DIKTAT MATA KULIAH

K I M I A O R G A N I K

Disusun oleh :Drs. Adiwarna

JURUSAN TEKNIK KIMIA FAKULTAS TEKNIK

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UNIVERSITAS MUHAMMADIYAH JAKARTA2008

DAFTAR ISI

TINJUAN MATAKULIAH

MODUL 1 : TEORI DASAR TENTANG ATOM DAN IKATAN ATOM Latihan Rangkuman Tes formatif

MODUL 2 : JENIS-JENIS IKATAN KIMIA Latihan Rangkuman Tes formatif

MODUL 3 : KONSEP DASAR SENYAWA ORGANIK

Latihan Rangkuman Tes formatif

MODUL 4 |: JENIS-JENIS REAKSI DALAM SENYAWA ORGANIK Latihan Rangkuman Tes formatif

MODUL 5 : JENIS-JENIS SENYAWA ORGANIK

Latihan Rangkuman Tes formatif

MODUL 6 : TEORI TENTANG STEREO KIMIA Latihan Rangkuman Tes formatif

MODUL 7 : PUSAT CHIRAL

Latihan Rangkuman Tes formatif

MODUL 8 : KARBOHIDRAT Latihan Rangkuman Tes formatif

MODUL 9 : ASAM AMINO DAN PROTEIN Latihan Rangkuman

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Tes formatif

MODUL 10 : TRIGLISERIDA Latihan Rangkuman Tes formatif

MODUL 11 : ALKALOID Latihan Rangkuman Tes formatif

MODUL 12 : TERPENOID Latihan Rangkuman Tes formatif

MODUL 13 : STEROID DAN SAPONIN Latihan Rangkuman Tes formatif

MODUL 14 : ASAM NUKLEAT Latihan Rangkuman Tes formatif

MODUL 15 : FLAVONOID DAN QUINONOID Latihan Rangkuman Tes formatif

MODUL 16 : POLIMER Latihan Rangkuman Tes formatif

KUNCI JAWABAN TES FORMATIFDAFTAR PUSTAKAKAMUS UMUM

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TINJAUAN MATAKULIAH

Mata kuliah kimia organik merupakan matakuliah MKDU yang diajarkan pada semester II. Diharapkan setelah mengikuti matakuliah ini mahasiswa dapat memahami tentang konfigurasi elektron dalam atom dan molekul, proses terjadinya ikatan kimia, sehingga dengan demikian mengetahui sifat keelektronegatifan, muatan formal, momen dipol, sifat keasaman dan kebasaan menurut bronsted Lowry dan Lewis.

Setelah mengetahui dasar-dasar pembentukan ikatan mahasiswa harus tahu tentang berbagai gugus fungsi pada senyawa organik, bermacam-macam reaksi organik, struktur senyawa organik, permberian nama senyawa organik, dan kelompok sennyawa organik.

Mata kuliah kimia organik meerupakan matakuliah wajib bagi mahasiswa yang mengikuti program S1 Teknik Kimia Fakultas Teknik Universitas Muhammadiyah jakarta. Setelah mengikuti matakkuliah ini mahasiswa diharapkan mampu :1. Mengetahui konsep dasar tentang atom dan molekul serta proses terjadinya ikatan kimia.2. Mengetahui sifat-sifat kimia akibat terjadinya ikatan kimia dan gugus fungsi pada senyawa

organik.3. Mengetahui struktur dan pemberian nama bermacam-macam senyawa organik dan

sintesanya.4. Bisa membedakan senyawa organik dengan senyawa anorganik.5. Mengenal tentang isomer, kiralitas berbagai senyawa organik serta bisa menentukan sifat

optis aktisnnya.6. Mengetahui bermacam-macam struktur senyawa karbohidrat, memberi nama, dan bisa

mengidentifikasi dengan reagen khusus.7. Mengetahui jenis-jenis struktur asam amino, pembentukan ikatan peptida menjadi protein,

serta bisa mensintesa asam amino dan protein..8. Mengetahui struktur ester trigliserida, bisa membedakan kelompok trigliserida, dan

mengenal biosintesa asam-asam lemak.9. Mengenal struktur dan bisa memeberi nama senyawa bahan alam yakni terpenoid, steroid,

alkaloid, flavonoid, quinonoid, saponin; dan bisa mensintesanya.10. Mengenal susunan struktur asam nukleat, bisa memberi nama, dan bisa menistesa.11. Menngenal struktur dan nama beberapa jenis-jenis polimer serta bisa mensintesanya.

Matakuliah kimia organik ini mempunyai bobot 3 sks dengan kode KIM008 terdiri dari 16 modulSebagai berikut :

MODUL 1 : Teori dasar tentang atom dan ikatan atom.MODUL 2 : Jenis-jenis ikatan kimia.MODUL 3 : Konsep dasar senyawa organik.MODUL 4 : Jenis-jenis reaksi dalam senyawa organik MODUL 5 : Jenis-jenis senyawa organik.MODUL 6 : Teori tentang stereo kimiaMODUL 7 : Pusat chiralMODUL 8 : KarbohidratMODUL 9 : Asam amino dan protein.MODUL 10 : TrigliseridaMODUL 11 : AlkaloidMODUL 12 : TerpenoidMODUL 13 : Steroid dan saponin

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MODUL 14 : Asam nukleatMODUL 15 : Flavonoid dan quinonoidMODUL 16 : PolimerMODUL I

I. TEORI DASAR TENTANG ATOM DAN IKATAN ATOMKonfigurasi Elektron dalam AtomMenurut Mendelejev electron dalam suatu atom akan mengisi orbital mulai dari tingkat energi terendah terlebih dahulu dari orbital 1s, 2s; 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d;

Tingkat energi tertinggi5f6p 6s4d5s4p3d4s3p3s2p2s1s

Tingkat energi terendahOrbital s maksimum terisi 2 elektron, orbital p maksimum terisi maksimum 6 elektron, orbital d maksimum terisi 10 elektron, orbital f maksimum terisi maksimum 14 elektron.Orbital s berbentuk lingkaran, orbital p berbentuk ellip yang tersusun dalam tiga dimensi, orbital d berbentuk ellip yang lebih lonjong yang tersusun dalam lima dimensi, dan orbital f berbentuk sangat lonjung yang tersusun dalam 7 dimensi

Orbital s Orbital p

Orbital d

Orbital d Orbital f

Contoh orbital s adalah atom hindrogen yang mempunyai 1 elektron ( biru ) dan 1 proton(merah).

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Tti

ngkat energi

Konfigurasi elektron dalam molekul

Susunan tingkat energi dasar dalam suatu atom dapat dijelaskan dengan teori orbital atom dan tingkat energinya. Ada tiga prinsip yang harus dipenuhi dalam pengisian electron pada suatu orbital atom :1. Electron mengisi orbital tingkat energi terendah terlebih dahulu.( prinsip Aufbau)2. Hanya maksimum dua electron menempati suatu orbital dengan spin yang berlawanan

arah. (prinsip ekslusi Pauli).3. Pengisian electron pada orbital bertingkat energi sama harus terisi satu-satu electron

terlebih dahulu ( Aturan Hund).

Orbital molekulBila dua atau lebih atom bergabung membentuk molekul unsur atau senyawa maka orbital electron molekul adalah merupakan gabungan dari orbital electron atom-atom penyusun molekul tersebut.

Contoh 1. orbital molekul H2

1s 1s H H H2

Contoh 2. Orbital molekul C2

2p

2p 2p 2p s

s s s

s s s C C s C2

Hibrida molekulBila dua electron dari dua atom bergabung membentuk ikatan maka akan terbentuk hibrida orbital. Bentuk hibrid orbital tergantung kepada asal orbital electron pembentuk ikatan, jika kedua electron tidak berpasangan dari dua atom berasal dari orbital s maka akan terbewntuk hibrid orbital s-s, jika dua electron tidak berpasangan dari dua atom berasal dari orbital s dan p maka akan terbewntuk hibrid orbital s-p, jika dua electron tidak berpasangan dari dua atom berasal dari orbital s dan d maka akan terbewntuk huibrid orbital s-d jika dua electron tidak berpasangan dari dua atom berasal dari orbital s dan f maka akan terbewntuk huibrid orbital s-f, jika dua electron tidak berpasangan dari dua atom berasal dari orbital p dan d maka akan terbewntuk huibrid orbital p-d, jika dua electron tidak berpasangan dari dua atom berasal dari orbital p dan f maka akan terbewntuk huibrid orbital p-f jika dua electron tidak berpasangan dari dua atom berasal dari orbital d dan f maka akan terbewntuk huibrid orbital d-f jika dua electron tidak berpasangan dari dua atom berasal dari orbital d dan d maka akan terbewntuk huibrid

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orbital d-d jika dua electron tidak berpasangan dari dua atom berasal dari orbital f dan f maka akan terbewntuk huibrid orbital f-f. jika electron tidak berpasangan dari dua atom berasal dari orbital 3s dan 3p maka akan terbewntuk huibrid orbital sp3, jika electron tidak berpasangan dari dua atom berasal dari orbital 2s dan 2p maka akan terbewntuk huibrid orbital sp2.

MODUL II

II. JENIS-JENIS IKATAN KIMIATeori tentang ikatan kimiaIkatan kimia antar atom-atom bisa terjadi apabila electron kulit terluar dari suatu atom ada yang tidak berpasangan. Suatu atom bisa berikatan dengan beberapa atom lain jika atom tersebut mempunyai banyak elekton terluar (valensi) tak berpasangan. Contohnya CH4.

2p

2p 2p H H H H s

s s

s s C s CH4

Sebelum membentuk molekul CH4 pada mulanya jika ikatan terjadi antara atom karbon dalam keadaan dasar dengan atom hindrogen hanya akan terbentuk molekul CH2, namun karbon sendiri bisa mengalami eksitasi dari keadaan dasar.

2p

2p + 2p H H s

s s

s s C s CH2

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2p

2p 2p 2p H H 1s 2s

+ 1s 2 s 2s 1s 2s

1s 1s 1 s 1s 4 H C C 1s Ground state Exited state CH4

Jenis-jenis ikatan kimiaIkatan ion

Ikatan ion terjadi dalam suatu molekul jika molekul tersebut mengalami polarisasi muatan elektrostatik. Hal ini terjadi pada molekul yang terdiri dari atom-atom elektropositif dan atom elektronegatif membentuk molekul polar. Molekul polar apabila dilarutkan dalam pelarut polar maka jarak atom elektropositif dan elektronegatif menjadi lebih jauh, sehingga dengan demikian akan terjadi polarisasi muatan elektrostatik, dimana electron terkuar dari atom elektro positif beredar pada inti atom elektronegatif sehingga atom elektropoasitif akan kekurangan electron dan kelebihan proton keadaan seperti ini membentuk mnuatan positif, sebaliknya atom elektronegatif akan menarik satu electron at6om elektropositif yang beredar pada inti atom elektronegatif sehingga terbentuklah muatan negative akibat atom elektronegatif kelebihan electron seperti reaksi berikut :

11Na8OH + H2O 10Na(H2O)2+ + 9OH-

Atom Natrium yang mempunyai 11 elektron dan 11 proton, pada molekul Na(H2O)2+

Elektron atom Natrium hanya 10 elektron yang mengitari orbit inti atom Natrium sehingga atom natrium kekurangan 1 elektron sehingga menjadi bermuatan (+) sedangkan atom oksigen yang mempunyai 8 elektron pada molekul OH- atom oksigen mempunyai 9 elektron sehingga bermuatan (-). Senyawa organic kebannyakan tidak ada yang berikatan polar tetapi hanya berikatan semi polar.

Ikatan kovalenIkatan kovalen adalah pemasangan electron tunggal dua atom atau lebih membentuk molekul tanpa terjadinya polarisasi electron. Kedua electron yang berpasangan dari dua atom berotasi mengitari inti dari masing-masing atom penyusunnya. Contohnya molekul CH4. :

H .

C. + 4 H. H C H

HIkatan hydrogen

Ikatan hydrogen adalah ikatan atom hydrogen dalam molekul senyawa asam Lewis dengan atom-atom elektronegatif dalam dasa Lewis. Ikatan hydrogen terjadi apabila electron dari atom hydrogen dalam suatu molekul beredarar pada orbit electron atom. Ikatan hydrogen dikenal dari sifat air yang mempunyai titik didih lebih tinggi dari molekul lain seperti H 2S

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dan CH4, air dengan berat molekul 18 mempunyai titik didih 100 oC sedangkan H2S dengan berat molekul 34 mempunyai titik didih 25 oC dan C2H6 dengan berat molekul 30 mempunyai titik didih 25 oC -5 C

ikatan vanderwallsLondon force

Bentuk-bentuk hibrida molekulHibridisasi adalah penggabungan electron yang tidak berpasangan dalam orbital suatu atom dengan electron yang tak berpasangan dari atom lain. Orbital yang terbentuk dari hibridisasi ini disebut hybrid orbital. Hybrida orbital bisa berbentuk s-s, s-p, s-d, s-f, p-p, p-d, p-f, d-d, d-f, atau f-f tergantung kepada asal orbital electron dari masing-masing atom. Hibrida molekul terjadi dari penggabungan electron tak berpasangan pada orbital dalam suatu molekul dari atom-atom penyusunnya. Bentuk hibrida molekul pada senyawa organic adalah sp3, sp2, dan sp. Sp3 ada pada senyawa alkana, sp2 ada pada senyawa alkena, dan sp ada pada senyawa alkuna.Hibridisasi sp3 pada molekul alkana berarti 1 dari 4 elektron orbital S hydrogen masuk ke orbital 2S dan 3 elektron orbital S dari hydrogen masuk ke 3 orbital P atom karbon. 2p

2p 2p 2p H H 1s 2s

+ 1s 2 s 2s 1s 2s

1s 1s 1 s 1s 4 H C C 1s Ground state Exited state CH4

Hibridisasi sp2 pada molekul alkena berarti 1 dari 3 elektron orbital S hydrogen masuk ke orbital 2S dan 3 elektron orbital S dari hydrogen masuk ke 3 orbital P dari atom karbon. 2p

2p 2p 2p H H 1s 2s

+ 1s 2 s 2s 1s 2s

1s 1s 1 s 1s 4 H C C 1s Ground state Exited state -CH3

Hibridisasi sp3 pada molekul alkana berarti 1 dari 4 elektron orbital S hydrogen masuk ke orbital 2S dan 3 elektron orbital S dari hydrogen masuk ke 3 orbital P dari atom karbon. 2p

2p 2p 2p H H 1s 2s

+ 1s 2 s 2s 1s 2s

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1s 1s 1 s 1s 4 H C C 1s Ground state Exited state -CH2

Polarisasi dan elektronegatifitas.Dari sekiian banyak molekul senyawa organic hanay sedikit sekalli yang ditemukan berupa senyawa dipolar. Akan tetapi kebanyakan molekul senyawa organic adalah polar. Hal ini menunjukan meskipun tidak bisa mengikuti muatan formal atom-atom, namun distribusi electron pada ikatan atom-atom tertentu adalah merupakan bentuk yang tidak simetris. Elektron-elektron Dallam atom tidak berpasangan secara sama oleh kedua inti atom.Sehinngga dengan demikian ikatan kimia pada atom-atom sangat ditentukan oleh kondisi atau situasi apakah yang terbentuk ikatan kovalen atau ionic. Belum ada penjelasan terperinci mengenai konsep ikatan kovalen polar, akan tetapi diperkirakan ikatan yang terjadi merupakan kelanjutan dari kemungkinan antara ikatan kovalen sempurna dengan distribusi elektron yang simetris atau sebaliknya, dan ikatan ionic sempurna atau sebaliknnya. Sebagai contohhnya ikatan -C-C- pada etana adalahh simetris, oleh karena itu merupakan ikatan kovalen sempurna, dua electron yang berikatan dipasangkan bersama antara kedua atom karbon yang setara. Sebaliknya ikatan pada Na-Cl adalah murni ionic dan terbentuk gaya tarik medan elektrostatik antara ion Natrium yang bermuatan positif dengan ion klorida yang bermuatan negative.

-C:C- ; -C :Cl ; Na+:Cl-

Pada ikatan -C-Cl kemungkinan besar terjadi penarikan electron agak kuat oleh suatu atom dari pada atom lainnya.Perbedaan kepolaran atom-atom yang berikatan mengakibatkan terjadinnya elektronegatifitas.

Tabel 1. . Elektronegatifitas dari beberapa jenis unsurUnsur elektronegatifitas unsur elektronegatifitasH 2.2 Mg 1.3Li 1.0 Al 1.6Be 1.6 Si 1.9B 2.0 P 2.2C 2.5 S 2.6N 3.0 Cl 3.1O 3.4 Br 3.0F 4.0 I 2.6Na 1.0 F 4

Unsur yang mempunyai elektronegatifitas diatas 2.5 dinyatakan dinyatakan lebih elektronegatif sedangkan unsur yang mempunyai elektronegatifitas dibawah 2.5 dinyatakan sebagai unsur elektropositif.

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S i f a t i o n i k

Dari table diatas terlihat bahwa antara atom karbon dan hydrogen mempunyai elektronegatifitas hamper sama maka iakatan –C-H adalah ikatan non polar. Unsur-unsur yang berada pada sebelah kanan table atom berkala seperti oksigen, florin, dan klorin adalah lebih elektronegatif dibandingkan dengan karbon, sehinga jika atom karbon berikatan dengan atom diatas akan menarik electron lebih kuat kearahnya dari pada atom karbon. Sehingga bila atom karbon berikatan dengan salah satu atom ini, maka terbetuklah ikatan terpolarisasi, sehingga dalam penggambarannya electron tertarik kearah atom elektronegatif ini dari pada atom karbon. Atom karbon akan menjadi bermuatan parsil positif yang dilambangkan dengan () dan atom elektronegatif akan menjadi bermuatan parsil negative yang dilambangkan dengan (). Sebagai contoh molekul H3C-Cl berikut :

H2,2

H2,2-C2,5 Cl-3,1

H2,2

Arah pada tanda panah digunakan untuk menunjukkan arah kepolaran. Berdasarkan konvensi kimia electron bergerah menuju arah panah. Ekor dari panah adalah atom yang kekurangan muatan electron dan kepala dari panah adalah atom yang kelebihan muatan electron. Unsur-unsur yang berada sebelah kiri table atom berkala adalah unsure-unsur elektropositif dari ppada karbon dan kurang kuat menarik electron.

Electron orbitalsElektron orbit atom dalam awan bentuk berbeda dan ukuran. Awan-awan elektron yang berlapis-lapis satu di dalam yang lain ke dalam satuan yang disebut kerang (berpikir boneka Rusia bersarang), dengan elektron menduduki shell, terkecil paling dalam memiliki keadaan energi terendah dan elektron di kulit, terbesar terluar memiliki keadaan energi tertinggi. Keadaan semakin tinggi energi, semakin besar energi potensial elektron memiliki, seperti sebuah batu di puncak bukit memiliki lebih energi potensial dari sebuah batu di dasar sebuah lembah. Konsep-konsep ini akan menjadi penting dalam memahami konsep-konsep kemudian seperti aktivitas optik senyawa kiral serta banyak hal menarik di luar bidang kimia organik (seperti bagaimana laser bekerja).

Wave nature of electrons

Elektron berperilaku sebagai partikel tapi juga sebagai gelombang. (Pekerjaan oleh Albert Einstein dan lain-lain mengungkapkan bahwa pada kenyataannya, cahaya dan materi semua berperilaku dengan sifat ganda, dan hal ini sangat jelas diamati pada partikel terkecil.) Salah satu hasil dari penelitian ini adalah bahwa elektron tidak hanya di orbit sederhana sekitar inti seperti yang kita bayangkan bulan untuk mengelilingi bumi, melainkan menempati ruang seolah-olah mereka gelombang pada permukaan bola.

Jika Anda melompat jumprope, Anda bisa membayangkan bahwa gelombang di tali adalah frekuensi fundamentalnya. Poin yang tinggi dan rendah jatuh tepat di tengah, dan tempat di mana tali tidak bergerak banyak (node) terjadi hanya pada dua ujung. Jika Anda menjabat tali cukup cepat dengan cara rythmic, menggunakan lebih banyak energi daripada Anda hanya akan lompat tali, Anda mungkin bisa membuat tali bergetar dengan panjang gelombang lebih pendek dari yang mendasar. Anda mereka mungkin melihat bahwa tali memiliki lebih dari satu tempat sepanjang

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panjangnya mana bergetar dari titik tertinggi ke tempat terendah. Selanjutnya, Anda akan melihat bahwa ada satu atau lebih tempat (atau node) sepanjang panjangnya mana tali

Or consider stringed musical instruments. The sound made by these instruments comes from the different ways, or modes the strings can vibrate. We can refer to these different patterns or modes of vibrations as linear harmonics. Going from there, we can recognize that a drum makes sound by vibrations that occur across the 2-dimensional surface of the drumhead. Extending this now into three dimensions, we think of the electron as vibrating across a 3-dimensional sphere, and the patterns or modes of vibration are referred to as spherical harmonics. The mathematical analysis of spherical harmonics were worked out by the French mathematician Legendre long before anyone started to think about the shapes of electron orbitals. The algebraic expressions he developed, known as Legendre polynomials, describe the three dimension shapes of electron orbitals in much the same way that the expression x2+y2 = z describes a circle (or, for that matter, a drumhead). Many organic chemists need never actually work with these equations, but it helps to understand where the pictures we use to think about the shapes of these orbitals come from.

Electron shells

Each different shell is subdivided into one or more orbitals, which also have different energy levels, although the energy difference between orbitals is less than the energy difference between shells.

Longer wavelengths have less energy; the s orbital has the longest wavelength allowed for an electron orbiting a nucleus and this orbital is observed to have the lowest energy.

Each shell in an orbital has a characteristic shape, and are named by a letter. They are: s, p, d, and f.

As one progresses up through the shells (represented by the principle quantum number n) more types of orbitals become possible.

S orbital

The s orbital is the orbital lowest in energy and is spherical in shape. Electrons in this orbital are in their fundamental frequency.

P orbital

The next lowest-energy orbital is the p orbital. Its shape is often described as like that of a dumbbell. There are three p-orbitals each oriented along one of the 3-dimensional coordinates x, y or z.

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These three different p orbitals can be referred to as the px, py, and pz.

The s and p orbitals are important for understanding most of organic chemistry as these are the orbitals that are occupied by the type of atoms that are most common in organic compounds.

D orbital

There are 5 types of d orbitals. Three of them are roughly X-shaped, as shown here, and might be viewed as being shaped like a crossed pair of dumbbells . They are referred to as dxy, dxz, and dyz. Like the p-orbitals, these three d orbitals have a node at the origin of the coordinate system where the three axes all come together. Unlike the p orbitals, however, these three d orbitals are not oriented along the x, y, or z axes, but instead are oriented in between them. The dxy orbital, for instance, lies in the xy plane, but the lobes of the orbital point out in between the x and y axes.

F orbital and beyond

There are 7 kinds of F orbitals, but we will not discuss their shapes here. F orbitals are filled in the elements of the lanthanide and actinide series, although electrons in these orbitals rarely come into play in organometallic reactions involving these elements.

Konfigurasi elektron dalam molekul

Susunan tingkat energi dasar dalam suatu atom dapat dijelaskan dengan teori orbital atom dan

tingkat energinya. Ada tiga prinsip yang harus dipenuhi dalam pengisian electron pada suatu

orbital atom :

1. Electron mengisi orbital tingkat energi terendah terlebih dahulu.( prinsip

Aufbau)

2. Hanya maksimum dua electron menempati suatu orbital dengan spin yang

berlawanan arah. (prinsip ekslusi Pauli).

3. Pengisian electron pada orbital bertingkat energi sama harus terisi satu-

satu electron terlebih dahulu ( Aturan Hund).

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Orbital molekul

Bila dua atau lebih atom bergabung membentuk molekul unsur atau senyawa maka orbital

electron molekul adalah merupakan gabungan dari orbital electron atom-atom penyusun

molekul tersebut.

Contoh 1. orbital molekul H2

1s 1s H H H2

Contoh 2. Orbital molekul C2

2p

2p 2p 2p s

s s s

s s s C C s C2

Hibrida molekulBila dua electron dari dua atom bergabung membentuk ikatan maka akan terbentuk

hibrida orbital. Bentuk hibrid orbital tergantung kepada asal orbital electron pembentuk

ikatan, jika kedua electron tidak berpasangan dari dua atom berasal dari orbital s maka

akan terbewntuk hibrid orbital s-s, jika dua electron tidak berpasangan dari dua atom

berasal dari orbital s dan p maka akan terbentuk hibrid orbital s-p, jika dua electron tidak

berpasangan dari dua atom berasal dari orbital s dan d maka akan terbewntuk huibrid

orbital s-d jika dua electron tidak berpasangan dari dua atom berasal dari orbital s dan f

maka akan terbewntuk huibrid orbital s-f, jika dua electron tidak berpasangan dari dua

atom berasal dari orbital p dan d maka akan terbewntuk huibrid orbital p-d, jika dua

electron tidak berpasangan dari dua atom berasal dari orbital p dan f maka akan

terbewntuk huibrid orbital p-f jika dua electron tidak berpasangan dari dua atom berasal

dari orbital d dan f maka akan terbewntuk huibrid orbital d-f jika dua electron tidak

berpasangan dari dua atom berasal dari orbital d dan d maka akan terbewntuk huibrid

orbital d-d jika dua electron tidak berpasangan dari dua atom berasal dari orbital f dan f

maka akan terbewntuk huibrid orbital f-f. jika electron tidak berpasangan dari dua atom

berasal dari orbital 3s dan 3p maka akan terbewntuk huibrid orbital sp3, jika electron tidak

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berpasangan dari dua atom berasal dari orbital 2s dan 2p maka akan terbewntuk huibrid

orbital sp2.

Teori tentang ikatan kimia

Ikatan kimia antar atom-atom bisa terjadi apabila electron kulit terluar dari suatu atom ada

yang tidak berpasangan. Suatu atom bisa berikatan dengan beberapa atom lain jika atom

tersebut mempunyai banyak elekton terluar (valensi) tak berpasangan. Contohnya CH4.

2p

2p 2p H H H H s

s s

s s C s CH4

Sebelum membentuk molekul CH4 pada mulanya jika ikatan terjadi antara atom karbon

dalam keadaan dasar dengan atom hindrogen hanya akan terbentuk molekul CH2, namun

karbon sendiri bisa mengalami eksitasi dari keadaan dasar.

2p

2p + 2p H H 2 s

2 s 2 s

1s

C 1 s CH2

2p

2p 2p 2p H H 1s 2s

+ 1s 2 s 2s 1s 2s

15

1s 1s 1 s 1s 4 H C C 1s Ground state Exited state CH4

Jenis-jenis ikatan kimia

Ikatan ion

Ikatan ion terjadi dalam suatu molekul jika molekul tersebut mengalami polarisasi muatan

elektrostatik. Hal ini terjadi pada molekul yang terdiri dari atom-atom elektropositif dan

atom elektronegatif membentuk molekul polar. Molekul polar apabila dilarutkan dalam

pelarut polar maka jarak atom elektropositif dan elektronegatif menjadi lebih jauh,

sehingga dengan demikian akan terjadi polarisasi muatan elektrostatik, dimana electron

terkuar dari atom elektro positif beredar pada inti atom elektronegatif sehingga atom

elektropoasitif akan kekurangan electron dan kelebihan proton keadaan seperti ini

membentuk mnuatan positif, sebaliknya atom elektronegatif akan menarik satu electron

at6om elektropositif yang beredar pada inti atom elektronegatif sehingga terbentuklah

muatan negative akibat atom elektronegatif kelebihan electron seperti reaksi berikut :

11Na8OH + H2O 10Na(H2O)2+ + 9OH-

Atom Natrium yang mempunyai 11 elektron dan 11 proton, pada molekul Na(H2O)2+

Elektron atom Natrium hanya 10 elektron yang mengitari orbit inti atom Natrium sehingga

atom natrium kekurangan 1 elektron sehingga menjadi bermuatan (+) sedangkan atom

oksigen yang mempunyai 8 elektron pada molekul OH- atom oksigen mempunyai 9

elektron sehingga bermuatan (-). Senyawa organic kebannyakan tidak ada yang berikatan

polar tetapi hanya berikatan semi polar.

Ikatan kovalen

Ikatan kovalen adalah pemasangan electron tunggal dua atom atau lebih membentuk

molekul tanpa terjadinya polarisasi electron. Kedua electron yang berpasangan dari dua

atom berotasi mengitari inti dari masing-masing atom penyusunnya. Contohnya molekul

CH4. :

H .

C. + H. H C H

16

H

Muatan Formal.

Cara penentuan muatan elektrostatik secara teoritis dapat ditentukan dengan cara

pendekatan muatan formal. Pada cara ini nilai muatan formal dihitung berdasarkan jumlah

electron kulit terluar dalam suatu atom dikurangi dengan jumlah electron kulit terluar

dalam atom berikatan atau jumlah electron kulit terluar

Jumlah electron jumlah electron

Mf = kulit terluar dalam – kulit terluar dalam.

Atom bebas atom berikatan

Jumlah electron ½ jumlah electron jumlah elektron

Mf = kulit terluar dalam – kulit terluar dalam – kulit terluar bebas

Atom bebas atom berikatan

Momen dipole

Bila masing-masing ikatan dalam suatu molekul polar memebentuk momen, maka

ikatan keseluruhan dalam molekul sering kali jadi polar. Kepolarann total ini bersal dari

penjumlahan kepolaran semua ikatan dan kontribusi pasangan electron bebas dalam

suatu molekul. Ukuran besaran keseluruhan kepolaran dari masing ikatan dalam molekul

ini disebut moment dipole. Kita bisa menggambarkan moment dipole dengan cara

berikut, misalkan ada suatu pusat grafitasi ari seluruh muatan positif dalam suatu

molekul, misalkan juga dalam molekul tersebut ada pusat grafitasi muatan negative. Jika

kedua pusat grafitasi muatan ini tak berimpitan maka molekul tersebut mempunyai

muatan listrik yang tak simetris dan mempunyai muatan total.. Moment dipole

(didefinisikan sebagai besaran unit muatan listrik (e) dikali jarak (d) antar pusat

muatan yang dinyatakan dalam satuan debye (D)

e ) x ( d ) x ( 10 18 ) = Debye

e = muatan listrik dalam satuan elektrostatik ( esu) = 4,8 x 10-10 esu

d = jarak antar muatan listrik statis dalam sentimeter

17

sebagai contoh jika satu proton dan satu electron ( e = 4.8 x 10 -10 esu ) dipisahkan satu sama

lainnya sejarak 1 Ao (10-8 cm) , maka didapatkan nilai sebagai berikut :

= ( 4.8 x 10 -10 esu ) (10-8 cm ) (1018) = 4,8 D

Secara percobaan akan relative lebih mudah mengukur moment dipole seperti nilainya

tercantum dalam table berikut :

Tabel 1. Nilai moment dipole dari beberapa senyawa kimia

senyawa Moment dipole

( D)

Senyawa Moment dipole

( D )

NaCl 9,00 H3C-CH3 0,00

CH3Cl 1,87 C6H6 0,00

H2O 1,85 BF3 0,00

H3COH 1,70 H2C=N+ =N- 1,50

NH3 1,47 H3C-N+=O

O-

3,46

H4C 0,00

CCl4 0,00

Dari table 1 diatas terlihat bahwa NaCl mempunyai nilai moment dipole yang luar biasa

besarnnya karena senyawwa ini bersifat ion. Nitrometana H3CNO2 mempunyai nilai moment

dipole cukup besar, karena senyawa ini mempunyai muatan formal pada dua atomnya.

Konsep dasar asam basa

Pengertian asam secara kimia menurut konsep bronsted-Lowry adalah suatu molekul yang

dapat melepaskan proton ( H+ ), sedangkan basa adalah suatu molekul menerima proton

( H+ ). Keasaman adalah kemampuan suatu senyawa melepaskan proton dan kebasaan

adalah kemampuan suatu senyawa untuk menerima proton. Menurut Lewis asam adalah

senyawa yang mempunyai orbital electron terluar yang kosong untuk ditempati oleh

pasangan electron bebas dari suatu molekul senyawa lain, sedangkan basa adalah suatu

18

molekul yang mempunyai pasangan electron bebas yang bisa didonorkan orbital electron

terluar yang kosong dari molekul lainnya.

MODUL III

III. KONSEP DASAR SENYAWA ORGANIK

Gugus fungsi senyawa organic

Penggolongan senyawa organic didasarkan atas reaktifitas dari gugus yang terdapat dalam

susunan molekul senyawa organic. Pusat reaksi senyawa organic berada pada gugus fungsi

tersebut. Ada senyawa organic yang mempunyai mono gugus fungsi dan ada pula yang

poli gugus fungsi. Gugus fungsi adalah merupakan bahagian dari molekul besar senyawa

organic. Ia tersusun dari atom atau gugus atom-atom yang menentukan karakteristik dari

kereaktifan kimia senyawa. Jika suatu senyawa hanya mempunyai satu gugus fungsi maka

senyawa itu disebut mono gugus fungsi. Jika suatu senyawa mempunyai banyak gugus

fungsi disebut poli gugus fungsi. Jenis-jenis gugus fungsi senyawa organic yang telah

diketahui

Tabel 2. Awalan substituen dimulai berurutan seuai abjad. (diluar jumlah substituen seperti di-, tri-, dll.), e.g. chlorofluoromethane, not fluorochloromethane. If there are multiple functional groups of the same type, either prefixed or suffixed, the position numbers are ordered numerically (thus ethane-1,2-diol, not ethane-2,1-diol.) The N position indicator for amines and amides comes before "1", e.g. CH3CH(CH3)CH2NH(CH3) is N,2-dimethylpropanamine.

Priority Functional group Formula Prefix Suffix

1Cations   e.g. Ammonium

 –NH4

+-onio-ammonio-

-onium-ammonium

2

Carboxylic acids   Thiocarboxylic acids   Selenocarboxylic acids   Sulfonic acids   Sulfinic acids   Sulfenic acids

–COOH–COSH–COSeH–SO3H–SO2H–SOH

carboxy-thiocarboxy-selenocarboxy-sulfo-sulfino-sulfeno-

-oic acid*-thioic acid*-selenoic acid*-sulfonic acid-sulfinic acid-sulfenic acid

3 Carboxylic acid derivatives   Esters

 –COOR

 R-oxycarbonyl-

 -R-oate

19

   Acyl halides   Amides   Imides   Amidines

–COX–CONH2

–CON=C<–C(=NH)NH2

halidealcanoyl-carbamoyl--imido-amidino-

-oyl halide*-amide*-imide*-amidine*

4Nitriles   Isocyanides

–CN–NC

cyano-isocyano-

-nitrile*isocyanide

5Aldehydes   Thioaldehydes

–CHO–CHS

formyl-thioformyl-

-al*-thial*

6Ketones   Thioketones

>CO>CS

oxo-thiono-

-one-thione

7

Alcohols   Thiols   Selenols   Tellurols

–OH–SH–SeH–TeH

hydroxy-sulfanyl-selanyl-tellanyl-

-ol-thiol-selenol-tellurol

8 Hydroperoxides –OOH hydroperoxy- -hydroperoxide

9Amines   Imines   Hydrazines

–NH2

=NH–NHNH2

amino-imino-hydrazino-

-amine-imine-hydrazine

10Ethers   Thioethers   Selenoethers

–O––S––Se–

-oxy--thio--seleno-

 

11Peroxides   Disulfides

–OO––SS–

-peroxy--disulfanyl-

 

*Note: These suffixes, in which the carbon atom is counted as part of the preceding chain, are the most commonly used. See individual functional group articles for more details.

20

Tabel 3. Jenis-jenis gugus fungsi senyawa organic yang telah dikenal

No Jenis senyawa Gugus fungsi Contohsenyawa

Akhiran nama

1 Alkana R-CH3 -ana2 Alkena C=C -ena3 Alkuna C C -una4 Halide alkana RX5 Alkanol ROH -ol6 Alkoksi alkana ROR -oksi -ana7 Alkanal R-C=O

H-al

8 Alkanon R-C=O R

-on

9 Alkil alkanoat R-C=O OR

-il -oat

10 Alkanoat R-C=O OH

-oat

11 Alkanoil halide R-C=O X

-oil -ida

12 Alkanoil amida R-C=O NH2

-oil –amida

13 Alkil amina RCH2NH2 -il -amina14 Alkil sianida RCH2-C N -il sianida15 Alkil nitrit RCH2NO2 -il nitrat16 Alkil sulfide RCH2SH -il sulfida17 Alkil Sulfoksi alkana R-SO-R -il sulfoksana18 Dialkil Sulfonat R-SO2-R -il 19 Alkil logam RCH2M -il logam20 Alkanoailsulfat R-C=O

OSO3H-oail sulfat

21 Alkanoail sianida R-C=O OCN

-oail sianida

22 Alkanoail halide R-C=O OX

-oail halida

23 Alkanoail amida R-C=O ONH2

-oail amida

24 Alkanoilsianida R-C=O CN

-oil sianidda

25 Alkil karbamat R-C=S SH

-il karbamat

26 diAlkil disulfida R-S-S-R’ -il disulfida27 Dialkil sulfida R-S-R -il sulfida28 Dithiokarbonat RO-C=S

SH-il thiokarbonat

29 Alkilsulfonat OR-O-S-OH O

Il sulfonat

21

30 Alkil sulfinat R-O-S=O OH

-il sulfinat

31 Dialkilsulfat R-O-SO2-OR -il sulfat32 Alkil posfat R-PO3H2 -il posfit33 Alkanoil posfit R-C=O

OPO3H2

-il posfat

34 Alkanoail posfat R-C=O PO4H2

Posfo alakanoat

35 Alkil posfat ROPO2H

Table of Functional groups

Alk is the prefix of the group (Meth, Eth, Prop, etc.)

Family StructureIUPAC

nomenclature

IUPAC nomenclature for cyclic parent chains (if different from

straight chains)

Common nomenclature

Alkyl groups

R— Alkyl - Alkyl

HalogensR—

halogenHalo'alkane - Alkyl halide

Alcohols R—OH Alkanol - Alkyl alcohol

Amines R—NH2 Alkanamine - Alkyl amine

Carboxylic acids

(Alk + 1)anoic acid

Cycloalkanecarboxylic acid -

Aldehydes Alkanal Cycloalkanecarboxaldehyde -

22

Ketones Alkanone -Alk(1)yl Alk(2)yl

ketone

Thiols R—SH Alkanethiol - -

Amides(Alk +

1)anamideCycloalkanecarboxamide -

EthersR1—O—

R2alkoxyalkane -

Alk(1)yl Alk(2)yl ether

EstersAlk(1)yl

Alk(2)aneoateAlk(1)yl Cycloalk(2)anecarboxylate

Alk(1)yl (Alk + 1)(2)anoate

Alcohols

Organic Chemistry/Overview of Functional Groups

The number of known organic compounds is quite large. In fact, there are many times more organic compounds known than all the other (inorganic) compounds discovered so far, about 7 million organic compounds in total. Fortunately, organic chemicals consist of a relatively few similar parts, combined in different ways, that allow us to predict how a compound we have never seen before may react, by comparing how other molecules containing the same types of parts are known to react.

These parts of organic molecules are called functional groups. The identification of functional groups and the ability to predict reactivity based on functional group properties is one of the cornerstones of organic chemistry.

Functional groups are specific atoms, ions, or groups of atoms having consistent properties. A functional group makes up part of a larger molecule.

For example, -OH, the hydroxy group that characterizes alcohols, is an oxygen with a hydrogen attached. It could be found on any number of different molecules.

Just as elements have distinctive properties, functional groups have characteristic chemistries. An -OH group on one molecule will tend to react similarly, although perhaps not identically, to an -OH on another molecule.

23

Organic reactions usually take place at the functional group, so learning about the reactivities of functional groups will prepare you to understand many other things about organic chemistry.

Memorizing Functional Groups

Don't deceive yourself and think that you can simply skim over the functional groups and move on. As you proceed through the text, the writing will be in terms of functional groups. It will be assumed that the student is familiar with most of the ones in the tables below. It's simply impossible to discuss chemistry without knowing the "lingo". It's like trying to learn French without first learning the meaning of some of the words.

One of the easiest ways to learn functional groups is by making flash cards. Get a pack of index cards and write the name of the functional group on one side, and draw its chemical representation on the other.

For now, a list of the most important ones you should know is provided here. Your initial set of cards should include, at the very least: Alkene, Alkyne, Alkyl halide (or Haloalkane), Alcohol, Aldehyde, Ketone, Carboxylic Acid, Acyl Chloride (or Acid Chloride), Ester, Ether, Amine, Sulfide, and Thiol. After you've learned all these, add a couple more cards and learn those. Then add a few more and learn those. Every functional group below is eventually discussed at one point or another in the book. But the above list will give you what you need to continue on.

And don't just memorize say, the names of the structures. To test yourself, try going through your cards and looking at the names and then drawing their structure on a sheet of paper. Then try going through and looking at the structures and naming them. Once you have the minimal list above memorized backwards and forwards, you're ready to move on. But don't stop learning the groups. If you choose to move on without learning the "lingo", then you're not going to understand the language of the chapters to come. Again, using the French analogy, it's like trying to ignore learning the vocabulary and then picking up a novel in French and expecting to be able to read it.

Functional groups containing ...

In organic chemistry functional groups are submolecular structural motifs, characterized by specific elemental composition and connectivity, that confer reactivity upon the molecule that contains them.

Common functional groups include:

Chemical class

Group FormulaGraphical Formula

Prefix Suffix Example

Acyl halideHaloformy

lRCOX haloformyl- -oyl halide

Acetyl chloride(Ethanoyl chloride)

24

Alcohol Hydroxyl ROH hydroxy- -ol

Methanol

Aldehyde Aldehyde RCHO oxo- -al

:Acetaldehyde(Ethanal)

Alkane Alkyl RHn alkyl- -ane

Methane

Alkene Alkenyl R2C=CR2 alkenyl- -ene

Ethylene(Ethene)

Alkyne Alkynyl RC≡CR' alkynyl- -yne Acetylene(Ethyne)

AmideCarboxami

deRCONR2

carboxamido-

-amideAcetamide

(Ethanamide)

Amines Primary amine

RNH2 amino- -amine

Methylamine(Methanamine)

25

Secondary amine

R2NH amino- -amine

Dimethylamine

Tertiary amine

R3N amino- -amine

Trimethylamine

4° ammonium

ionR4N+ ammonio- -ammonium

Choline

Azo compound

Azo(Diimide)

RN2R' azo- -diazene

Methyl orange

Toluene derivative

BenzylRCH2C6H5

RBnbenzyl-

1-(substituent)tol

uene Benzyl bromide(1-Bromotoluene)

CarbonateCarbonate

esterROCOOR

alkyl carbonate

Carboxylate

Carboxylate

RCOO− carboxy- -oateSodium acetate

(Sodium ethanoate)

Carboxylic acid

Carboxyl RCOOH carboxy- -oic acid

Acetic acid(Ethanoic acid)

CyanatesCyanate ROCN cyanato- alkyl cyanate

Thiocyanate

RSCNthiocyanato

-alkyl

thiocyanate

26

Ether Ether ROR' alkoxy-alkyl alkyl

ether Diethyl ether(Ethoxyethane)

Ester Ester RCOOR' -oate Ethyl butyrate(Ethyl butanoate)

Haloalkane Halo RX halo- alkyl halide Chloroethane(Ethyl chloride)

Hydroperoxide (see organic

peroxide)

Hydroperoxy

ROOHhydroperox

y-alkyl

hydroperoxide Methyl ethyl ketone peroxide

Imine

Primary ketimine

RC(=NH)R' imino- -imine

Secondary ketimine

RC(=NR)R' imino- -imine

Primary aldimine

RC(=NH)H imino- -imine

Secondary aldimine

RC(=NR')H imino- -imine

Isocyanide Isocyanide RNC isocyano-alkyl

isocyanide

Isocyanates

Isocyanate RNCO isocyanato-alkyl

isocyanate

Isothiocyanate

RNCSisothiocyan

ato-alkyl

isothiocyanate Allyl isothiocyanate

Ketone Ketone RCOR' keto-, oxo- -one Methyl ethyl ketone

(Butanone)Nitrile Nitrile RCN cyano-

alkanenitrilealkyl cyanide

Benzonitrile

27

(Phenyl cyanide)

Nitro compound

Nitro RNO2 nitro-  

Nitromethane

Nitroso compound

Nitroso RNO nitroso-  

Nitrosobenzene

Peroxide Peroxy ROOR peroxy- alkyl peroxideDi-tert-butyl

peroxide

Benzene derivative

Phenyl RC6H5 phenyl- -benzene

Cumene(2-phenylpropane)

Phosphine Phosphino R3P phosphino- -phosphane Methylpropylphosphane

Phosphodiester

PhosphateHOPO(OR)

2

phosphoric acid

di(substituent) ester

di(substituent) hydrogenphosp

hateDNA

Phosphonic acid

PhosphonoRP(=O)(OH)2

phosphono-substituent phosphonic

acid Benzylphosphonic acid

Phosphate PhosphateROP(=O)

(OH)2phospho-

Glyceraldehyde 3-phosphate

Pyridine derivative

Pyridyl RC5H4N

4-pyridyl(pyridin-4-

yl)

3-pyridyl(pyridin-3-

yl)

2-pyridyl(pyridin-2-

yl)

-pyridine

Nicotine

28

Sulfide RSR'di(substituent)

sulfide Dimethyl sulfide

Sulfone Sulfonyl RSO2R' sulfonyl-di(substituent)

sulfone Dimethyl sulfone(Methylsulfonylmet

hane)

Sulfonic acid

Sulfo RSO3H sulfo-substituent

sulfonic acidBenzenesulfonic

acid

Sulfoxide Sulfinyl RSOR' sulfinyl-di(substituent)

sulfoxide

Diphenyl sulfoxide

Thiol Sulfhydryl RSHmercapto-, sulfanyl-

-thiol Ethanethiol(Ethyl mercaptan)

Note: The table above is adapted from the Functional Groups table on Wikipedia.

Combining the names of functional groups with the names of the parent alkanes generates a powerful systematic nomenclature for naming w:organic compounds.

The non-hydrogen atoms of functional groups are always associated with each by covalent bonds, as well as with the rest of the molecule. When the group of atoms is associated with the rest of the molecule primarily by ionic forces, the group is referred to more properly as a polyatomic ion or complex ion. And all of these are called radicals, by a meaning of the term radical that predates the free radical.

The first carbon after the carbon that attaches to the functional group is called the alpha carbon.

Retrieved from "http://en.wikibooks.org/wiki/Organic_Chemistry/Overview_of_Functional_Groups"

MODUL IV

IV. JENIS-JENIS REAKSI DALAM SENYAWA ORGANIK

Jenis-jenis reaksi pada senyawa organic

29

a. Reaksi addisi

C = C + H2 CH – CH

b. Reaksi substitusi

RX + OH- ROH + X-

c. Reaksi eliminasi

RCHX-CH3 RCH=CH2 + HX

d. Reaksi oksidasi

RCH2OH + KMnO4 RC =O H

e. Reaksi reduksi

RCN + LiAlH4 RCH2NH2

f. Reaksi penataan ulang (rearrangement)

H3C-H2C-CH=CH-CH=CH2 H3C-H2C=CH-CH=CH-CH3

Pada dasarnya jenis-jenis reaksi pada senyawa organic ada 3 ienis yakni reaksi polar, reaksi

radikal, dan reaksi perisiklik.

Kecepatan dan mekanisme reaksi senyawa organic

Energi ikatan pada senyawa organic

MODUL V

V. JENIS-JENIS SENYAWA ORGANIK

Alkana

30

Rumus umum senyawa alkana adalah CnH2n+2

Pemberian nama senyawa organic dengan dua standar :

1. IUPAC

2. Trivial :

a. Nama dagang

b. Nama sumber

c. Nama local

d Nama penemu

Pemberian nama pada deret homolog senyawa alkana dengan dua cara yaitu :

IUPAC ( International Union Pure and Applied Chemistry )

Rantai molekul lurus

Tata nama senyawa homolog hidrokarbon pada senyawa organic rantai lurus menurut IUPAC

adalah berdasarkan jumlah atom karbonnya sebagai berikut :

Senyawa Nama Senyawa Nama Senyawa NamaCH4 Metana C34H44 tetratriakontana C67H136 heptaHeksa kontanaC2H6 Etana C35H46 pentatriakontana C68H138 oktaHeksa kontanaC3H8 Propane C36H48 heksatriakontana C69H140 nonaHeksa kontanaC4H10 Butane C37H50 heptatriakontana C70H142 HeptakontanaC5H12 Pentane C38H52 oktatriakontana C71H144 henHeptakontanaC6H14 Heksana C39H54 nonatriakontana C72H146 DoHeptakontanaC7H16 Heptana C40H56 Tetrakontana C73H148 triHeptakontanaC8H18 Oktana C41H58 hentetrakontana C74H150 tetraHeptakontanaC9H20 Nonana C42H60 Dotetrakontana C75H152 pentaHeptakontanaC10H22 Dekana C43H62 Tritetrakontana C76H154 heksaHeptakontanaC11H24 Undekana C44H64 tetratetrakontana C77H156 heptaHeptakontanaC12H26 Dodekana C45H66 pentatetrakontana C78H158 oktaHeptakontanaC13H28 Tridekana C46H68 heksatetrakontana C79H160 nonaHeptakontanaC14H30 Tetradekana C47H70 heptatetrakontana C80H162 OktakontanaC15H32 Pentadekana C48H72 oktatetrakontana C81H164 henOktakontanaC16H34 Heksadekana C49H74 nonatetrakontana C82H166 doOktakontanaC17H36 Heptadekana C50H102 Pentakontana C83H168 triOktakontanaC18H38 Oktadekana C51H104 Henpentakontana C84H170 tetraOktakontanaC19H40 Nonadekana C52H106 dopentakontana C85H172 pentaOktakontanaC20H42 Eikosana C53H108 tripentakontana C86H174 heksaOktakontanaC21H44 Heneikosana C54H110 tetrapentakontana C87H176 heptaOktakontanaC22H46 Dokosana C55H112 pentapentakontana C88H178 oktaOktakontanaC23H48 Trikosana C56H114 heksapentakontana C89H180 nonaOktakontanaC24H50 Tetrakosana C57H116 heptapentakontana C90H182 NonakontanaC25H52 Pentakosana C58H118 Oktapentakontana C91H184 henNonakontanaC26H54 Heksakosana C59H120 nonapentakontana C92H186 doNonakontanaC27H56 Heptakosana C60H122 Heksa kontana C93H188 triNonakontanaC28H58 Oktakosana C61H124 HenHeksa kontana C94H190 tetraNonakontanaC29H60 Nonakosana C62H126 doHeksa kontana C95H192 pentaNonakontanaC30H62 Triakontana C63H128 triHeksa kontana C96H194 heksaNonakontanaC31H64 Hentriakontana C64H130 tetraHeksa kontana C97H196 HeptaNonakontanaC32H66 Dotriakontana C65H132 pentaHeksa kontana C98H198 oktaNonakontanaC33H68 Tritriakontana C66H134 heksaHeksa kontana C99H200 nonaNonakontanaC100H202 Hektana C400H802 Tetraktana C700H1402 HeptaktanaC200H402 Diktana C500H1002 Pentaktana C800H1602 Oktaktana

31

C300H6002 Triktana C600H12002 Heksaktana C900H1802 NonaktanaC1000H2002 kiliana C400H8002 Tetraliana C700H14002 HeptalianaC2000H4002 Dilianatana C500H10002 Penliaana C800H16002 OktalianaC3000H6002 Triliana C600H1202 Heksaliana C900H18002 Nonaliana

Rantai molekul bercabang

Untuk rantai molekul bercabang harus dipenuhi kaidah rantai lurus dan rantai lingkar.

Rantai molekul lurus bercabang lurus

Untuk pemberian nama senyawa hidrokarbon berantai molekul lurus bercabang didasarkan

pada aturan berikut :

a. rantai dasar ditentukan berdasarkan rantai molekul terpanjang.

14 15 16 17 18 19 20

CH3-CH2 CH3-(CH2)2 CH3 CH2-CH2-CH2-CH2-CH2-CH2-CH3

7 8 9 10 11 12 13

H3C-CH2-CH-CH2-CH - CH-CH2-CH2-CH-CH-CH3

1

(CH2)5-CH3 CH2CH3 CH3

7 isobutil, 9 propil, 10 etil, 11 metil, 13 isopropil eikosana

Tulisan berwarna biru menunjukkan rantai utama sedangkan tulisan berwarna merah

menunjukkan substituen.

b. Penomoran atom karbon pada hidrokarbon dimulai pada gugus tersubstitusi yang paling

dekat ke ujung rantai.

c. Bila ada beberapa gugus yang sama tersubstitusi pada rantai utama maka dinamai dengan

awalan di, tri dan seterusnya. Contoh

11 10 9 8 7 6 5 4 3 2 1

H3C-CH2-CH-CH2-CH2-CH-CH2-CH2-CH2-CH-CH3

CH3 CH3 CH3

2,6, 9 trimetil undekana

d. Urutan gugus tersubstitusi dimulai dari gugus berurutan dimulai berdasrkan abjad atau

nomor urut gugus yang paling dekat ke awal rantai

11 10 9 8 7 6 5 4 3 2 1

H3C-CH2-CH-CH2-CH2-CH-CH2-CH2-CH2-CH-CH3

CH3 CH3 CH3

32

2,6, 9 trimetil undekana

Rantai molekul lurus bercabang lingkar

H3C-CH2-CH-CH2-CH2-CH-CH2-CH2-CH2

Nonil sikloheksana

rantai molekul lingkar bercabang lingkar

Rantai molekul lingkar terkondensasi.

Rantai lingkara. Siklo propana

b. Siklo butana

e. Siklo pentana

f. Siklo heksana

g. Siklo oktana

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IUPAC nomenclature of organic chemistry

From Wikipedia, the free encyclopediaJump to: navigation, search

The IUPAC nomenclature of organic chemistry is a systematic method of naming organic chemical compounds as recommended[1] by the International Union of Pure and Applied Chemistry (IUPAC). Ideally, every organic compound should have a name from which an unambiguous structural formula can be drawn. There is also an IUPAC nomenclature of inorganic chemistry. See also phanes nomenclature of highly complex cyclic molecules.

The main idea of IUPAC nomenclature is that every compound has one and only one name, and every name corresponds to only one structure of molecules (i.e. a one-one relationship), thereby reducing ambiguity.

For ordinary communication, to spare a tedious description, the official IUPAC naming recommendations are not always followed in practice except when it is necessary to give a concise definition to a compound, or when the IUPAC name is simpler (viz. ethanol against ethyl alcohol). Otherwise the common or trivial name may be used, often derived from the source of the compound (See Sec 14. below)

Basic principles

In chemistry, a number of prefixes, suffixes and infixes are used to describe the type and position of functional groups in the compound.

The steps to naming an organic compound are:

1. Identify the parent hydrocarbon chain (The longest continuous chain of carbon atoms) 2. Identify the functional group, if any (If more than one, use the one with highest

precedence as shown here) 1. Identify the position of the functional group in the chain. 2. Number the carbon atoms in the parent chain. The functional group should end up

the least number possible (as there are two ways of numbering—right to left and left to right). The number (in Arabic numerals, i.e. 1, 2, 3....) is written before the name of the functional group suffix (such as -ol, -one, -al, etc.). If the group is a group that can only exist at the end of any given chain (such as the carboxylic acid and aldehyde groups), it need not be numbered.NOTE: If there are no functional groups, number in both directions, find the numbers of the side-chains (the carbon chains that are not in the parent chain) in both directions. The end result should be such that the first number should be the least possible. In the event of the first numbers being the same for two methods of numbering, the sum of the numbers of the side chains should be made the least possible; for example, 2,2,5-trimethylhexane (2 + 2 + 5 = 9) is preferred over 2,5,5-trimethylhexane (2 + 5 + 5 = 12), as they both start with '2', but the sum of the numbers of the former is less.

3. Identify the side-chains and number them. Side chains are the carbon chains that are not in the parent chain, but are branched off from it.If there is more than one of the same type of side-chain, add the prefix (di-, tri-, etc.) before it. The numbers for that type of side chain will be grouped in ascending order and

34

written before the name of the side-chain. If there are two side-chains with the same alpha carbon, the number will be written twice. Example: 2,2,3-trimethyl...

4. Identify the remaining functional groups, if any, and name them by the name of their ions (Such as hydroxy for -OH, oxy for =O , oxyalkane for O-R, etc.).Different side-chains and functional groups will be grouped together in alphabetical order. (The prefixes di-, tri-, etc. are not taken into consideration for grouping alphabetically. For example, ethyl comes before dihydroxy or dimethyl, as the "e" in "ethyl" precedes the "h" in "hydroxy" and the "m" in "dimethyl" alphabetically. The "di" is not considered in both cases.) In the case of there being both side chains and secondary functional groups, they should be written mixed together in one group rather than in two separate groups.

5. Identify double/triple bonds. Number them with the number of the carbon atom at the head of the bond (i.e the carbon atom with the lesser number that it is attached to). For example a double bond between carbon atoms 3 and 4 is numbered as 3-ene. Multiple bonds of one type (double/triple) are named with a prefix (di-, tri-, etc.). If both types of bonds exist, then use "ene" before "yne" e.g. "6 13 diene 19 yne"If all bonds are single, use "ane" without any numbers or prefixes.

6. Arrange everything like this: Group of side chains and secondary functional groups with numbers made in step 3 + prefix of parent hydrocarbon chain (eth, meth) + double/triple bonds with numbers (or "ane") + primary functional group suffix with numbers.Wherever it says "with numbers", it is understood that between the word and the numbers, you use the prefix(di-, tri-)

7. Add punctuation: 1. Put commas between numbers (2 5 5 becomes 2,5,5) 2. Put a hyphen between a number and a letter (2 5 5 trimethylhexane becomes 2,5,5-

trimethylhexane) 3. Successive words are merged into one word (trimethyl hexane becomes

trimethylhexane)NOTE: IUPAC uses one-word names throughout. This is why all parts are connected.

The finalized name should look like this: #,#-di<side chain>-#-<secondary functional group><-#-<side chain>-#,#,#-tri<secondary functional group><parent chain suffix><If all bonds are single bonds, use "ane">-#,#-di<double bonds>-#-<triple bonds>-#-<primary functional group>NOTE: # is used for a number. The group secondary functional groups and side chains may not look the same as shown here, as the side chains and secondary functional groups are arranged alphabetically. The di- and tri- have been used just to show their usage. (di- after #,#, tri- after #,#,# , etc.)

Example:Here is a sample molecule with the parent carbons numbered:

35

For simplicity, here is an image of the same molecule, where the hydrogens in the parent chain are removed and the carbons are shown by their numbers:

Now, we go by the steps:

1. The parent hydrocarbon chain has 23 carbons. It is called tricos-. 2. The functional groups with the highest precedence are the two ketone groups.

1. The groups are on carbon atoms 3 & 9. As there are two, we write 3,9-dione. 2. The numbering of the molecule is based on the ketone groups. when numbering

from left to right, the ketone groups get numbered 3 and 9.when numbering from right to left, the ketone groups get numbered 15 and 21. The sum of 3 & 9 (12) is less than the sum of 15 & 21 (36). Therefore, the numbering is done left to right, and the ketones are numbered 3 & 9.

3. The side chains are: an ethyl- at carbon 4, an ethyl- at carbon 8, and a butyl- at carbon 12.NOTE:The -O-CH3 at carbon atom 15 is not a side chain, but it is a methoxy functional group

o There are two ethyl- groups, so they are combined to create, 4,8-diethyl. o The side chains shall be grouped like this: 12-butyl-4,8-diethyl. (But this is not the

final grouping, as functional groups may be added in between.) 2. The secondary functional groups are: a hydroxy- at carbon 5, a chloro- at carbon 11, a

methoxy- at carbon 15, and a bromo- at carbon 18. Grouped with the side chains, we get 18-bromo-12-butyl-11-chloro-4,8-diethyl-5-hydroxy-15-methoxy

3. There are two double bonds: one between carbons 6 & 7, and one between carbons 13 & 14. They will be called 6,13-diene. There is one triple bond between carbon atoms 19 & 20. It will be called 19-yne

4. The arrangement(with punctuation) is: 18-bromo-12-butyl-11-chloro-4,8-diethyl-5-hydroxy-15-methoxytricos-6,13-diene-19-yne-3,9-dione

The final name is 18-bromo-12-butyl-11-chloro-4,8-diethyl-5-hydroxy-15-methoxytricos-6,13-diene-19-yne-3,9-dione.

AlkanesMain article: Alkanes

Straight-chain alkanes take the suffix "-ane" and are prefixed depending on the number of carbon atoms in the chain, following standard rules. The first few are:

36

Number of carbo

ns

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 20 30

PrefixMeth

Eth

Prop

But

Pent

Hex

Hept

Oct

Non

Dec

Undec

Dodec

Tridec

Tetradec

Pentadec

Eicos

Triacont

For example, the simplest alkane is CH4 methane, and the nine-carbon alkane CH3(CH2)7CH3 is named nonane. The names of the first four alkanes were derived from methanol, ether, propionic acid and butyric acid, respectively. The rest are named with a Greek numeric prefix, with the exceptions of nonane which has a Latin prefix, and undecane and tridecane which have mixed-language prefixes.

Cyclic alkanes are simply prefixed with "cyclo-", for example C4H8 is cyclobutane and C6H12 is cyclohexane.

Branched alkanes are named as a straight-chain alkane with attached alkyl groups. They are prefixed with a number indicating the carbon the group is attached to, counting from the end of the alkane chain. For example, (CH3)2CHCH3, commonly known as isobutane, is treated as a propane chain with a methyl group bonded to the middle (2) carbon, and given the systematic name 2-methylpropane. However, although the name 2-methylpropane COULD be used, it is easier and more logical to call it simply methylpropane - the methyl group could not possible occur on any of the other cabon atoms (that would lengthen the chain and result in butane, not propane) and therefore the use of the number "2" is not necessary.

If there is ambiguity in the position of the substituent, depending on which end of the alkane chain is counted as "1", then numbering is chosen so that the smallest number is used. For example, (CH3)2CHCH2CH3 (isopentane) is named 2-methylbutane, not 3-methylbutane.

37

If there are multiple side-branches of the same size alkyl group, their positions are separated by commas and the group prefixed with di-, tri-, tetra-, etc., depending on the number of branches (e.g. C(CH3)4 2,2-dimethylpropane). If there are different groups, they are added in alphabetical order, separated by commas or hyphens: 3-ethyl-4-methylhexane. The longest possible main alkane chain is used; therefore 3-ethyl-4-methylhexane instead of 2,3-diethylpentane, even though these describe equivalent structures. The di-, tri- etc. prefixes are ignored for the purpose of alphabetical ordering of side chains (e.g. 3-ethyl-2,4-dimethylpentane, not 2,4-dimethyl-3-ethylpentane).

.

] Cyclic compounds

Cycloalkanes and aromatic compounds can be treated as the main parent chain of the compound, in which case the position of substituents are numbered around the ring structure. For example, the three isomers of xylene CH3C6H4CH3, commonly the ortho-, meta-, and para- forms, are 1,2-dimethylbenzene, 1,3-dimethylbenzene, and 1,4-dimethylbenzene. The cyclic structures can also be treated as functional groups themselves, in which case they take the prefix "cycloalkyl-" (e.g. "cyclohexyl-") or for benzene, "phenyl-".

The IUPAC nomenclature scheme becomes rapidly more elaborate for more complex cyclic structures, with notation for compounds containing conjoined rings, and many common names such as phenol, furan, indole, etc. being accepted as base names for compounds derived from them.

38

Order of precedence of groups

When compounds contain more than one functional group, the order of precedence determines which groups are named with prefix or suffix forms. The highest precedence group takes the suffix, with all others taking the prefix form. However, double and triple bonds only take suffix form (-en and -yn) and are used with other suffixes.

Common nomenclature - trivial names

Common nomenclature is an older system of naming organic compounds. Instead of using the prefixes for the carbon skeleton above, another system is used. The pattern can be seen below.

Number of carbons

Prefix as in new system

Common name for alcohol

Common name for aldehyde

Common name for acid

1 MethMethyl alcohol (wood alcohol)

Formaldehyde Formic acid

2 EthEthyl alcohol (grain alcohol)

Acetaldehyde Acetic acid

3 Prop Propyl alcohol Propionaldehyde Propionic acid

4 But Butyl alcohol Butyraldehyde Butyric acid

5 Pent Amyl alcohol Valeraldehyde Valeric acid

6 Hex - Caproaldehyde Caproic acid

7 Hept Enanthyl alcohol Enanthaldehyde Enanthoic acid

8 Oct Capryl alcohol Caprylaldehyde Caprylic acid

9 Non - Pelargonaldehyde Pelargonic acid

10 Dec Capric alcohol Capraldehyde Capric acid

39

12 Dodec Lauryl alcohol Lauraldehyde Lauric acid

14 Tetradec - Myristaldehyde Myristic acid

16 Hexadec Cetyl alcohol Palmitaldehyde Palmitic acid

17 Heptadec - - Margaric acid

18 Octadec Stearyl alcohol Stearaldehyde Stearic acid

20 Icos Arachidyl alcohol - Arachidic acid

22 Docos Behenyl alcohol - Behenic acid

24 Tetracos Lignoceryl alcohol - Lignoceric acid

26 Hexacos Cerotinyl alcohol - Cerotinic acid

28 Octacos Montanyl alcohol - Montanic acid

30 Triacont Melissyl alcohol - Melissic acid

Aldehydes

The common name for an aldehyde is derived from the common name of the corresponding carboxylic acid by dropping the word acid and changing the suffix from -ic or -oic to -aldehyde.

Formaldehyde Acetaldehyde

Ions

The IUPAC nomenclature also provides rules for naming ions.

Hydron

Hydron is a generic term for hydrogen cation; protons, deuterons and tritons are all hydrons.

40

Parent hydride cations

Simple cations formed by adding a hydron to a hydride of a halogen, chalcogen or nitrogen-family element are named by adding the suffix "-onium" to the element's root: H4N+ is ammonium, H3O+ is oxonium, and H2F+ is fluoronium. Ammonium was adopted instead of nitronium, which commonly refers to NO2

+.

If the cationic center of the hydride is not a halogen, chalcogen or nitrogen-family element then the suffix "-ium" is added to the name of the neutral hydride after dropping any final 'e'. H5C+ is methanium, HO-O+H2 is dioxidanium (HO-OH is dioxidane), and H2N-N+H3 is diazanium (H2N-NH2 is diazane).

Cations and substitution

The above cations except for methanium are not, strictly speaking, organic, since they do not contain carbon. However, many organic cations are obtained by substituting another element or some functional group for a hydrogen.

The name of each substitution is prefixed to the hydride cation name. If many substitutions by the same functional group occur, then the number is indicated by prefixing with "di-", "tri-" as with halogenation. (CH3)3O+ is trimethyloxonium. CH3F3N+ is trifluoromethylammonium.

Nama trivial ( nama lain )

Nama trivial adalah penamaan senyawa hidrokarbon tidak dengan sistematika seperti pada

aturan pemberian nama menurut IUPAC, tetapi dengan nama tertentu seperti :

a. nama dagang

b. nama lokal

c. nama penemu

d. nama sumber

Sintesa alkana

H2Oa. RX + Na R-R + NaXb. C = C + H2 CH – CH

c. R-CH2X+ R’Na RCH2-R’ + NaX

d. RC CH + H2 RCH2-CH3

e. R-X + Mg RMgX + H2O RH + MgXOH

e. CO + 3H2 CH4 + H2O

41

Alkena

Main articles: Alkenes and Alkynes

Alkenes are named for their parent alkane chain with the suffix "-ene" and an infixed number indicating the position of the double-bonded carbon in the chain: CH2=CHCH2CH3 is but-1-ene. Multiple double bonds take the form -diene, -triene, etc., with the size prefix of the chain taking an extra "a": CH2=CHCH=CH2 is buta-1,3-diene. Simple cis and trans isomers are indicated with a prefixed cis- or trans-: cis-but-2-ene, trans-but-2-ene. More complex geometric isomerisations are described using the Cahn Ingold Prelog priority rules.

Alkynes are named using the same system, with the suffix "-yne" indicating a triple bond: ethyne (acetylene), propyne (methylacetylene).

Pemberian nama

a. Alkena alifatik

aa. senyawa Alkena alifatik mempunyai struktur molekul terbuka seperti berikut :

R-CH = CH2

Tabel 5. Nama alkena alifatik sesuai dengan deret homolog alkana, akhiran nama ana diganti

dengan ena. Contoh

Senyawa Nama Senyawa Nama Senyawa NamaCH4 Metena C34H44 tetratriakontena C67H136 heptaHeksa kontenaC2H6 Etena C35H46 pentatriakontena C68H138 oktaHeksa kontenaC3H8 Propena C36H48 heksatriakontena C69H140 nonaHeksa kontenaC4H10 Butena C37H50 heptatriakontena C70H142 HeptakontenaC5H12 Pentena C38H52 oktatriakontena C71H144 henHeptakontena

42

C6H14 Heksena C39H54 nonatriakontena C72H146 DoHeptakontenaC7H16 Heptena C40H56 Tetrakontena C73H148 triHeptakontenaC8H18 Oktena C41H58 hentetrakontena C74H150 tetraHeptakontenaC9H20 Nonena C42H60 Dotetrakontena C75H152 pentaHeptakontenaC10H22 Dekena C43H62 Tritetrakontena C76H154 heksaHeptakontenaC11H24 Undekena C44H64 tetratetrakontena C77H156 heptaHeptakontenaC12H26 Dodekena C45H66 pentatetrakontena C78H158 oktaHeptakontenaC13H28 Tridekena C46H68 heksatetrakontena C79H160 nonaHeptakontenaC14H30 Tetradekena C47H70 heptatetrakontena C80H162 OktakontenaC15H32 Pentadekena C48H72 Oktatetrakontena C81H164 henOktakontenaC16H34 Heksadekena C49H74 nonatetrakontena C82H166 doOktakontenaC17H36 Heptadekena C50H102 Pentakontena C83H168 triOktakontenaC18H38 Oktadekena C51H104 Henpentakontena C84H170 tetraOktakontenaC19H40 Nonadekena C52H106 dopentakontena C85H172 pentaOktakontenaC20H42 Eikosena C53H108 tripentakontena C86H174 heksaOktakontenaC21H44 Heneikosena C54H110 tetrapentakontena C87H176 heptaOktakontenaC22H46 Dokosena C55H112 pentapentakontena C88H178 oktaOktakontenaC23H48 Trikosena C56H114 heksapentakontena C89H180 nonaOktakontenaC24H50 Tetrakosena C57H116 heptapentakontena C90H182 NonakontenaC25H52 Pentakosena C58H118 Oktapentakontena C91H184 henNonakontenaC26H54 Heksakosena C59H120 nonapentakontena C92H186 doNonakontenaC27H56 Heptakosena C60H122 Heksa kontena C93H188 triNonakontenaC28H58 Oktakosena C61H124 HenHeksa kontena C94H190 tetraNonakontenaC29H60 Nonakosena C62H126 doHeksa kontena C95H192 pentaNonakontenaC30H62 Triakontena C63H128 triHeksa kontena C96H194 heksaNonakontenaC31H64 Hentriakontena C64H130 tetraHeksa kontena C97H196 HeptaNonakontenaC32H66 Dotriakontena C65H132 pentaHeksa kontena C98H198 oktaNonakontenaC33H68 Tritriakontena C66H134 heksaHeksa kontena C99H200 nonaNonakontenaC100H202 Hektena C400H802 Tetraktena C700H1402 HeptahektenaC200H402 Diktena C500H1002 Pentaktena C800H1602 OktaktenaC300H6002 Triktena C600H12002 Heksaktena C900H1802 NonaktenaC1000H2002 Kiliena C400H8002 Tetraliena C7000H14002 HeptalienaC2000H4002 Diliena C5000H10002 Pentaliena C8000H16002 OktalienaC3000H6002 Triliena C6000H1202 Heksaliena C9000H18002 Nonaliena

CH3-CH2-CH2-CH = CH2 Pentena

b. alkapoliena

Nama senyawa alkapoliena alifatik disesuaikan dengan nama homolog alkana, akhiran ana

diganti menjadi poliena tergantung banyaknya gugus ena yang terdapat dalam senyawa

tersebut contoh :

1 2 3 4 5 6 7 8 9 10

CH2=CH-CH=CH-CH2-CH=CH-CH2-CH = CH2

1,3,6,9 dekatetraenaPada senyawa ini Karenna ada 4 gugus ena maka namanya mendapat akhiran tetraena

c.Alkena siklik

43

Siklopropena siklobutadiena siklopentena

Alkenes are aliphatic hydrocarbons containing carbon-carbon double bond and general formula CnH2n.

Naming Alkenes

Alkenes are named as if they were alkanes, but the "-ane" suffix is changed to "-ene". If the alkene contains only one double bond and that double bond is terminal (the double bond is at one end of the molecule or another) then it is not necessary to place any number in front of the name.

butane: C4H10 (CH3CH2CH2CH3)butene: C4H8 (CH2=CHCH2CH3)

If the double bond is not terminal (if it is on a carbon somewhere in the center of the chain) then the carbons should be numbered in such a way as to give the first of the two double-bonded carbons the lowest possible number, and that number should precede the "ene" suffix with a dash, as shown below.

correct: pent-2-ene (CH3CH=CHCH2CH3)incorrect: pent-3-ene (CH3CH2CH=CHCH3)The second one is incorrect because flipping the formula horizontally results in a lower number for the alkene.

If there is more than one double bond in an alkene, all of the bonds should be numbered in the name of the molecule - even terminal double bonds. The numbers should go from lowest to highest, and be separated from one another by a comma. The IUPAC numerical prefixes are used to indicate the number of double bonds.

octa-2,4-diene: CH3CH=CHCH=CHCH2CH2CH3

deca-1,5-diene: CH2=CHCH2CH2CH=CHCH2CH2CH2CH3

Note that the numbering of "2-4" above yields a molecule with two double bonds separated by just one single bond. Double bonds in such a condition are called "conjugated", and they represent an enhanced stability of conformation, so they are energetically favored as reactants in many situations and combinations.

EZ Notation

Earlier in stereochemistry, we discussed cis/trans notation where cis- means same side and trans- means opposite side. Alkenes can present a unique problem, however in that the cis/trans notation sometimes breaks down. The first thing to keep in mind is that alkenes are planar and there's no rotation of the bonds, as we'll discuss later. So when a substituent is on one side of the double-bond, it stays on that side.

44

cis-but-2-ene and trans-but-2-ene

The above example is pretty straight-forward. On the left, we have two methyl groups on the same side, so it's cis-but-2-ene. And on the right, we have them on opposite sides, so we have trans-but-2-ene. So in this situation, the cis/trans notation works and, in fact, these are the correct names.

(Z)-3-methylpent-2-ene and (E)-3-methylpent-2-ene

From the example above, how would you use cis and trans? Which is the same side and which is the opposite side? Whenever an alkene has 3 or 4 differing substituents, one must use the what's called the EZ nomenclature, coming from the German words, Entgegen (opposite) and Zusammen (same).

E: Entgegen, opposite sides of double bondZ: Zusammen, same sides (zame zides) of double bond

Let's begin with (Z)-3-methylpent-2-ene. We begin by dividing our alkene into left and right halves. On each side, we assign a substituent as being either a high priority or low priority substituent. The priority is based on the atomic number of the substituents. So on the left side, hydrogen is the lowest priority because its atomic number is 1 and carbon is higher because its atomic number is 6.

On the right side, we have carbon substituents on both the top and bottom, so we go out to the next bond. On to the top, there's another carbon, but on the bottom, a hydrogen. So the top gets high priority and the bottom gets low priority.

Because the high priorities from both sides are on the same side, they are Zusammen (as a mnemonic, think 'Zame Zide').

Now let's look at (E)-3-methylpent-2-ene. On the left, we have the same substituents on the same sides, so the priorities are the same as in the Zusammen version. However, the substituents are reversed on the right side with the high priority substituent on the bottom and the low priority

45

substituent on the top. Because the High and Low priorities are opposite on the left and right, these are Entgegen, or opposite.

The system takes a little getting used to and it's usually easier to name an alkene than it is to write one out given its name. But with a little practice, you'll find that it's quite easy.

Comparison of E-Z with cis-trans

(Z)-but-2-ene (E)-but-2-ene

cis-but-2-ene trans-but-2-ene

To a certain extent, the Z configuration can be regarded as the cis- isomer and the E as the trans- isomers. This correspondence is exact only if the two carbon atoms are identically substituted.

In general, cis-trans should only be used if each double-bonded carbon atom has a hydrogen atom (i.e. R-CH=CH-R').

IUPAC Gold book on cis-trans notation.

IUPAC Gold book on E-Z notation.

Properties

Alkenes are molecules with carbons bonded to hydrogens which contain at least two sp2 hybridized carbon atoms. That is, to say, at least one carbon-to-carbon double bond, where the carbon atoms, in addition to an electron pair shared in a sigma (σ) bond, share one pair of electrons in a pi (π) bond between them.

The general formula for an aliphatic alkene is: CnH2n -- e.g. C2H4 or C3H6

Diastereomerism

Restricted rotation

Because of the characteristics of pi-bonds, alkenes have very limited rotation around the double bonds between two atoms. In order for the alkene structure to rotate the pi-bond would first have to be broken - which would require about 60 or 70 kcal of energy. For this reason alkenes have different chemical properties based on which side of the bond each atom is located.

For example, but-2-ene exists as two diastereomers:

46

(Z)-but-2-ene (E)-But-2-ene

cis-but-2-ene trans-but-2-ene

Relative stability

Observing the reaction of the addition of hydrogen to 1-butene, (Z)-2-butene, and (E)-2-butene, we can see that all of the products are butane. The difference between the reactions is that each reaction has a different energy: -30.3 kcal/mol for 1-butene, -28.6 kcal/mol for (Z)-2-butene and -27.6 kcal/mol for (E)-2-butene. This illustrates that there are differences in the stabilities of the three species of butene isomers, due to the difference in how much energy can be released by reducing them.

The relative stability of alkenes may be estimated based on the following concepts:

An internal alkene (the double bond not on the terminal carbon) is more stable than a terminal alkene (the double bond is on a terminal carbon).

Internal alkenes are more stable than terminal alkenes because they are connected to more carbons on the chain. Since a terminal alkene is located at the end of the chain, the double bond is only connected to one carbon, and is called primary (1°). Primary carbons are the least stable. In the middle of a chain, a double bond could be connected to two carbons. This is called secondary (2°). The most stable would be quaternary (4°).

In general, the more and the bulkier the alkyl groups on a sp2-hybridized carbon in the alkene, the more stable that alkene is.

A trans double bond is more stable than a cis double bond.

Reactions

Preparation

There are several methods for creating alcohols.[1] Some of these methods, such as the Wittig reaction, we'll only describe briefly in this chapter and instead, cover them in more detail later in the book. For now, it's enough to know that they are ways of creating alkenes.

Dehydrohalogenation of Haloalkanes

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Synthesis of alkene by dehydrohalogenation

Dehydrohalogenation is a very common method for creating alkenes. It uses the E2 elimination mechanism that we'll discuss in detail at the end of this chapter. The base used is generally a strong base such as KOH (potassium hydroxide) or NaOCH3 (sodium methoxide). The haloalkane must have a hydrogen and halide 180° from each other on neighboring carbons. If there is no hydrogen 180° from the halogen on a neighboring carbon, the reaction will not take place.

Dehalogenation of Vicinal Dibromides

Synthesis of alkene via debromination of vicinal dihalides using Sodium Iodide

Synthesis of alkene via debromination of vicinal dihalides using Zinc

The dehalogenation of vicinal dihalides (halides on two neighboring carbons, think "vicinity") is another method for synthesizing alkenes. The reaction can take place using either sodium iodide in a solution of acetone, or it can be performed using zinc dust in a solution of either heated ethanol or acetic acid.

This reaction can also be performed with magnesium in ether, though the mechanism is different as this actually produces, as an intermediate, a Grignard reagent that reacts with itself and and causes an elimination, resulting in the alkene.

Dehydration of alcohols

Synthesis of alkene by dehydration of an alcohol

When an alcohol is treated with a strong acid, for example H2SO4, it is converted into an alkene. The mechanism of this reaction is fairly straight-forward. A lone pair from the alcohol's oxygen attacks a proton (H+) from the acid. This create a hydronium ion which easily leaves the carbon, creating a carbocation. The acid, now deficient a proton, and the carbocation wanting to stabilize and get a bond, a hydrogen from an adjacent bond leaves, without its electron, and the adjacent carbons form a pi bond, creating the alkene.

The underlying mechanism is the E1 mechanism which is described below.

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Wittig Reaction

Synthesis of alkene via Wittig reaction

Markovnikov's Rule

Before we continue discussing reactions, we need to take a detour and discuss a subject that's very important in Alkene reactions, "Markovnikov's Rule." This is a simple rule stated by the Russian Vladmir Markovnikov in 1869, as he was showing the orientation of addition of HBr to alkenes.

His rule states:"When an unsymmetrical alkene reacts with a hydrogen halide to give an alkyl halide, the hydrogen adds to the carbon of the alkene that has the greater number of hydrogen substituents, and the halogen to the carbon of the alkene with the fewer number of hydrogen substituents" (This rule is often compared to the phrase: "The rich get richer and the poor get poorer." Aka, the Carbon with the most Hydrogens gets another Hydrogen and the one with the least Hydrogens gets the halogen)

This means that the nucleophile of the electophile-nucleophile pair is bonded to the position most stable for a carbocation, or partial positive charge in the case of a transition state.

Examples

CH2 = CH − CH3 + H − Br − > CH3 − CHBr − CH3 Here the Br attaches to the middle carbon over the terminal carbon, because of Markovnikov's rule, and this is called a Markovnikov product.

Markovnikov product

The product of a reaction that follows Markovnikov's rule is called a Markovnikov product. in

Markovnikov addition

Markovnikov addition is an addition reaction which follows Markovnikov's rule, producing a Markovnikov product.

Anti-Markovnikov addition

Certain reactions produce the opposite of the Markovnikov product, yielding what is called anti-Markovnikov product. That is, hydrogen ends up on the more substituted carbon of the double bond. The hydroboration/oxidation reaction that we'll discuss shortly, is an example of this, as are reactions that are conducted in peroxides.

A modernized version of Markovnikov's rule often explains the "anti-Markovnikov" behavior. The original Markovnikov rule predicts that the hydrogen (an electrophile) being added across a double bond will end up on the carbon with more hydrogens. Generalizing to all electrophiles, it is really the electrophile which ends up on the carbon with the greatest number of hydrogens.

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Usually hydrogen plays the role of the electrophile; however, hydrogen can also act as an nucleophile in some reactions. The following expansion of Markovnikov's rule is more versitile:

"When an alkene undergoes electrophilic addition, the electrophile adds to the carbon with the greatest number of hydrogen substituents. The nucleophile adds to the more highly substituated carbon."

Or more simply:

"The species that adds first adds to the carbon with the greatest number of hydrogens."

The fact that some reactions reliably produce anti-Markovnikov products is actually a powerful tool in organic chemistry. For example, in the reactions we discuss below, we'll show two different ways of creating alcohols from alkenes: Oxymercuration-Reduction and Hydroboration/Oxidation. Oxymercuration produces a Markovnikov product while Hydroboration produces an anti-Markovnikov product. This gives the organic chemist a choice in products without having to be stuck with a single product that might not be the most desired.

Why it works

Markovnikov's rule works because of the stability of carbocation intermediates. Experiments tend to reveal that carbocations are planar molecules, with a carbon that has three substituents at 120° to each other and a vacant p orbital that is perpendicular to it in the 3rd plane. The p orbital extends above and below the trisubstituent plane.

This leads to a stabilizing effect called hyperconjugation. Hyperconjugation is what happens when there is an unfilled (antibonding or vacant) C-C π orbital and a filled C-H σ bond orbital next to each other. The result is that the filled C-H σ orbital interacts with the unfilled C-C π orbital and stabilizes the molecule. The more highly substituted the molecule, the more chances there are for hyperconjugation and thus the more stable the molecule is.

Another stabilizing effect is an inductive effect.

Exceptions to the Rule

There are a few exceptions to the Markovnikov rule, and these are of tremendous importance to organic synthesis.

1. HBr in Hydrogen Peroxide: Due to formation of free radicals, and the mechanism in which it reacts, the alkyl free radical forms at the middle atom, where it is most stable, and a hydrogen attaches itself here. Note here hydrogen addition is the second step, unlike in the above example.

Addition reactions

Hydroboration

Hydroboration is a very useful reaction in Alkenes, not as an end product so much as an intermediate product for further reactions. The primary one we'll discuss below is the Hydroboration/Oxidation reaction which is actually an a hydroboration reaction followed by a completely separate oxidation reaction.

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Hydroboration mechanism

The addition of BH3 is a concerted reaction in that several bonds are broken and formed at the same time. Hydroboration happens in what's called syn-addition because the boron and one of its hydrogens attach to the same side of the alkene at the same time. As you can see from the transition state in the center of the image, this produces a sort of box between the two alkene carbons and the boron and its hydrogen. In the final step, the boron, along with its other two hydrogens, remains attached to one carbon and the other hydrogen attaches to the adjacent carbon.

This description is fairly adequate, however, the reaction actually continues to happen and the -BH2 continue to react with other alkenes giving an R2BH and then again, until you end up with a complex of the boron atom attached to 3 alkyl groups, or R3B.

This trialkyl-boron complex is then used in other reactions to produce various products.

B2H6 complex BH3-THF complex

Borane, in reality, is not stable as BH3. Boron, in this configuration has only 6 electrons and wants 8, so in its natural state it actually creates the B2H6 complex shown on the left.

Furthermore, instead of using B2H6 itself, BH3 is often used in a complex with tetrahydrofuran (THF) as shown in the image on the right.In either situation, the result of the reactions are the same.

Hydroboration/Oxidation

[2]

Hydroboration/Oxidation reaction

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Hydroboration/Oxidation is a 2 part reaction. The first step is the above described hydroboration. After this step, the trialkyl-boron complex is oxidized with hydrogen peroxide (H2O2) in a basic solution. The result is an alcohol.

As mentioned in the discussion of Markovnikov's rule, Hydroboration produces an anti-markovnikov product in that the hydrogen attaches to the most substituted side of the alkene instead of the least substituted side.

Oxymercuration/Reduction

[2]

Oxymercuration/Reduction of 1-propene

Another useful method for creating alcohols from alkenes, is Oxymercuration/Reduction. Like the Hydroboration/Reduction, this too is a two-step process. In the first step, the alkene is reacted with mercury acetate in water and THF. In the second step, the mercury is reduced by the addition of sodium borohydride.

Unlike Hydroboration/Oxidation, this reaction, as can be seen in the image above, follows Markovnikov's rule. The hydrogen is added to the least substituted side and the hydroxyl group is added to the most substituted side.

Hydroboration/Oxidation of 1-propene

By way of comparison, here's the same reaction using the Hydroboration/Oxidation reaction. Here, the hydrogen ends up on the most substituted side and the hydroxyl group on the least substituted side, in an anti-Markovnikov product.

Catalytic addition of hydrogen

Catalytic hydrogenation of alkenes produce the corresponding alkanes. The reaction is carried out under pressure in the presence of a metallic catalyst. Common industrial catalysts are based on platinum, nickel or palladium, but for laboratory syntheses, Raney's nickel (an alloy of nickel and aluminium) is often employed.

The catalytic hydrogenation of ethylene to yield ethane proceeds thusly:

CH2=CH2 + H2 + catalyst → CH3-CH3

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Electrophilic addition

Most addition reactions to alkenes follow the mechanism of electrophilic addition. An example is the Prins reaction, where the electrophile is a carbonyl group.

Halogenation

Addition of elementary bromine or chlorine to alkenes yield vicinal dibromo- and dichloroalkanes, respectively.

The decoloration of a solution of bromine in water is an analytical test for the presence of alkenes: CH2=CH2 + Br2 → BrCH2-CH2Br

The reaction works because the high electron density at the double bond causes a temporary shift of electrons in the Br-Br bond causing a temporary induced dipole. This makes the Br closest to the double bond slightly positive and therefore an electrophile.

Hydrohalogenation

Addition of hydrohalic acids like HCl or HBr to alkenes yield the corresponding haloalkanes.

an example of this type of reaction: CH3CH=CH2 + HBr → CH3-CHBr-CH3

If the two carbon atoms at the double bond are linked to a different number of hydrogen atoms, the halogen is found preferentially at the carbon with less hydrogen substituents (Markovnikov's rule).

Addition of a carbene or carbenoid yields the corresponding cyclopropane

Oxidation

Alkenes are oxidized with a large number of oxidizing agents. In the presence of oxygen, alkenes burn with a bright flame to carbon dioxide and water. Catalytic oxidation with oxygen or the reaction with percarboxylic acids yields epoxides.

Reaction with ozone in ozonolysis leads to the breaking of the double bond, yielding two aldehydes or ketones: R1-CH=CH-R2 + O3 → R1-CHO + R2-CHO + H2O

This reaction can be used to determine the position of a double bond in an unknown alkene.

Polymerization

Polymerization of alkenes is an economically important reaction which yields polymers of high industrial value, such as the plastics polyethylene and polypropylene. Polymerization can either proceed via a free-radical or an ionic mechanism.

f. Alkena aromatik

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Menurut kaidah Huckel senyawa alkena menjadi aromatic apabila mempunyai jumlah electron

4n+2 dengan struktur senyawa lingkar, dimana n adalah bilangan bulat dari 0,1 , 2, 3, 4,

5, dst. Setiap ikatan ganda karbon C=C mempunyai dua electron

Siklo heksa triena (benzen)

Pada senyawa sikloheksatriena ini ada 3 x 2 = 6 elektron

Teori aromatisitas didasarkan pada sifat benzene yang mengikuti postulat Huckel berikut :

1. Benzen adalah senyawa lingkar terkonyugasi dengan rumus C6H6.

2. Benzen biasanya tidak stabil. Panas hidrogenasinya adalah 36 kcal/mole lebih kecil dari

pada panas hidrogenasi triena normal.

3. Benzen adalah molekul simetris, berupa bidang datar, dan merupakan heksagonal, semua

ikatan -C-C-C- adalah 120o, dan panjang semua ikatan –C-C- adalah 1,39 Ao

4. Benzen bisa mengalami reaksi substitusi yang mengikuti konyugasi lingkar, dari pada

reaksi addisi elektrofilik yang mengakibatkan putusnya konyugasi ikatan .

5. Benzen memenuhi teori hibrida resonansi yang strukturnya merupakan peralihan antara

dua bentuk struktur menurut Kekule.

Kekule Siklo heksa triena (benzena)

Benzen ( Fisher ) Benzen ( Dewar ) Benzen (Ladenburg )

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6. Ikatan pada benzen dapat lagi dengan menggunakan teori orbital molekul. Enam orbital p

bergabung membentuk enem orbital molekul benzene dengan resultante delokalisasi

electron melelui sistim konyugasi.

.

After understanding the usefulness of unsaturated compound, or conjugated system, we hope to explore the unique structure of aromatic compounds, including why benzene should not be called 1,3,5-cyclohexatriene because it is more stable than a typical triene, and seemingly unreactive. Called "aromatic" initially because of its fragrance, aromaticity now refers to the stability of compounds that are considered aromatic, not only benzene. Any cyclic compound with 4n+2 pi electrons in the system is aromatic. The stability of aromatic compounds arises because all bonding orbitals are filled and low in energy.

History of Aromatics

Early in the 19th century, advances in equipment, technique and communications resulted in chemists discovering and experimenting with novel chemical compounds. In the course of their investigations they stumbled across a different kind of stable compound with the molecular formula of C6H6. Unable to visualize what such a compound might look like, the scientists invented all sorts of models for carbon-to-carbon bonding -- many of which were not entirely stable -- in order to fit what they had observed to what they expected the C6H6 compound to look like.

Benzene (which is the name that was given to the aromatic compound C6H6) is probably the most common and industrially important aromatic compound in wide use today. It was discovered in 1825 by Michael Faraday, and its commercial production from coal tar (and, later on, other natural sources) began in earnest about twenty-five years later. The structure of benzene emerged during the 1860s, the result of contributions from several chemists, most famously that of Kekulé.

Scientists of the time did not have the benefit of understanding that electrons are capable of delocalization, so that all carbon atoms could share the same π-bond electron configuration equally. Huckel was the first to apply the new theory of quantum mechanics to clearly separating σ and π electrons. He went on to develop a theory of π electron bonding for benzene, which was the first to explain the electronic origins of aromaticity.

Benzene Structure

Benzene is a hexagonal ring of six carbon atoms connected to each other through one p-orbital per carbon. Its chemical formula is C6H6, and its structure is a hexagonal ring of carbons sharing symmetrical bonds, with all six hydrogen atoms protruding outwards from the carbon ring, but in the same plane as the ring. The p-orbital system contains 6 electrons, and one way to distribute the electrons yields the following structure:

However, another resonance form of benzene is possible, where the single bonds of the first structure are replaced with double bonds, and the double bonds with single bonds. These two resonance forms are co-dominant in benzene. (Other forms, such as a structure with a π bond

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connecting opposite carbons, are possible but negligible.) Thus, each bond in benzene has been experimentally shown to be of equal length and strength, and each is accounted as approximately a "1.5" bond instead of either a single or double bond alone.

Electron density is shared between carbons, in effect yielding neither a single nor a double bond, but a sort of one-and-a-half bond between each of the six carbons. Benzene has a density of negative charge both above and below the plane formed by the ring structure. Although benzene is very stable and does not tend to react energetically with most substances, electrophilic compounds may be attracted to this localized electron density and such substances may form a bond with the aromatic benzene ring.

An electron delocalisation ring can be used to show in a single picture both dominant resonance forms of benzene:

Benzene Properties

Benzene is a colorless, flammable liquid with a sweet aroma and carcinogenic effects. The aromatic properties of benzene make it far different from other alkenes in many ways.

Benzene ReactionsMain article: Aromatic reactions

Unlike alkenes, aromatic compounds such as benzene undergo substitution reactions instead of addition reactions. The most common reaction for benzene to undergo is electrophilic aromatic substitution (EAS), although in a few special cases, it can undergo nucleophilic aromatic substitution.

Benzene Health Effects

In the body, benzene is metabolized, and benzene exposure may have quite serious health effects. Breathing in very high levels of benzene can result in death, while somewhat lower (but still high) levels can cause drowsiness, dizziness, rapid heart rate, headaches, tremors, confusion, and unconsciousness. Eating or drinking foods containing high levels of benzene can cause vomiting, irritation of the stomach, dizziness, sleepiness, convulsions, rapid heart rate, and even death.

The major effect of benzene from chronic (long-term) exposure is to the blood. Benzene damages the bone marrow and can cause a decrease in red blood cells, leading to anemia. It can also cause excessive bleeding and depress the immune system, increasing the chance of infection. Some women who breathed high levels of benzene for many months had irregular menstrual periods and a decrease in the size of their ovaries. It is not known whether benzene exposure affects the developing fetus in pregnant women or fertility in men, however animal studies have shown low birth weights, delayed bone formation, and bone marrow damage when pregnant animals breathed benzene.

The US Department of Health and Human Services (DHHS) also classifies benzene as a human carcinogen. Long-term exposure to high levels of benzene in the air can cause leukemia, a

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potentially fatal cancer of the blood-forming organs. In particular, Acute Myeloid Leukemia (AML) may be caused by benzene.

Aromaticity

Aromaticity in organic chemistry does not refer to whether or not a molecule triggers a sensory response from olfactory organs (whether it "smells"), but rather refers to the arrangement of electron bonds in a cyclic molecule. Many molecules that have a strong odor (such as diatomic chlorine Cl2) are not aromatic in structure -- odor has little to do with chemical aromaticity. It was the case, however, that many of the earliest-known examples of aromatic compounds had distinctively pleasant smells. This property led to the term "aromatic" for this class of compounds, and hence the property of having enhanced stability due to delocalized electrons came to be called "aromaticity".

Definition

Aromaticity is a chemical property in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone. It can also be considered a manifestation of cyclic delocalization and of resonance.

This is usually considered to be because electrons are free to cycle around circular arrangements of atoms, which are alternately single- and double-bonded to one another. These bonds may be seen as a hybrid of a single bond and a double bond, each bond in the ring identical to every other. This commonly-seen model of aromatic rings was developed by Kekulé. The model for benzene consists of two resonance forms, which corresponds to the double and single bonds' switching positions. Benzene is a more stable molecule than would be expected of cyclohexatriene, which is a theoretical molecule.

Theory

By convention, the double-headed arrow indicates that two structures are simply hypothetical, since neither can be said to be an accurate representation of the actual compound. The actual molecule is best represented by a hybrid (average) of most likely structures, called resonance forms. A carbon-carbon double bond is shorter in length than a carbon-carbon single bond, but aromatic compounds are perfectly geometrical (that is, not lop-sided) because all the carbon-carbon bonds have the same length. The actual distance between atoms inside an aromatic molecule is intermediate between that of a single and that of a double bond.

A better representation than Lewis drawings of double and single bonds is that of the circular π bond (Armstrong's inner cycle), in which the electron density is evenly distributed through a π bond above and below the ring. This model more correctly represents the location of electron density within the aromatic molecule's overall structure. The single bonds are sigma (σ) bonds formed with electrons positioned "in line" between the carbon atoms' nuclei. Double bonds consist of one "in line" σ bond and another non-linearly arranged bond -- a π-bond. The π-bonds

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are formed from the overlap of atomic p-orbitals simultaneously above and below the plane of the ring formed by the "in line" σ-bonds.

Since they are out of the plane of the atoms, π orbitals can interact with each other freely, and thereby they become delocalized. This means that, instead of being tied to one particular atom of carbon, each electron can be shared by all the carbon atoms in an aromatic ring. Thus, there are not enough electrons to form double bonds on all the carbon atoms, but the "extra" electrons strengthen all of the bonds of the ring equally.

Characteristics

An aromatic compound contains a set of covalently-bound atoms with specific characteristics:

1. A delocalized conjugated pi system, most commonly an arrangement of alternating single and double bonds

2. Coplanar structure, with all the contributing atoms in the same plane 3. Contributing atoms arranged in one or more rings 4. A number of pi delocalized electrons that is even, but not a multiple of 4. (This is known

as Hückel's rule. Permissible numbers of π electrons include 6, 10, 14, and so on) 5. Special reactivity in organic reactions such as electrophilic aromatic substitution and

nucleophilic aromatic substitution

Whereas benzene is aromatic (6 electrons, from 3 double bonds), cyclobutadiene is not, since the number of π delocalized electrons is 4, which is not satisfied by any n integer value. The cyclobutadienide (2−) ion, however, is aromatic (6 electrons). An atom in an aromatic system can have other electrons that are not part of the system, and are therefore ignored for the 4n + 2 rule. In furan, the oxygen atom is sp2 hybridized. One lone pair is in the π system and the other in the plane of the ring (analogous to C-H bond on the other positions). There are 6 π electrons, so furan is aromatic.

Aromatic molecules typically display enhanced chemical stability, compared to similar non-aromatic molecules. The circulating (that is, delocalized) π electrons in an aromatic molecule generate significant local magnetic fields that can be detected by NMR techniques. NMR experiments show that protons on the aromatic ring are shifted substantially further down-field than those on aliphatic carbons. Planar monocyclic molecules containing 4n π electrons are called anti-aromatic and are, in general, destabilized. Molecules that could be anti-aromatic will tend to alter their electronic or conformational structure to avoid this situation, thereby becoming merely non-aromatic.

Aromatic molecules are able to interact with each other in so-called π-π stacking: the π systems form two parallel rings overlap in a "face-to-face" orientation. Aromatic molecules are also able to interact with each other in an "edge-to-face" orientation: the slight positive charge of the substituents on the ring atoms of one molecule are attracted to the slight negative charge of the aromatic system on another molecule.

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Monosubstituted Benzenes

Benzene is a very important basic structure which is useful for analysis and synthesis in most aspects of organic chemistry. The benzene ring itself is not the most interesting or useful feature of the molecule; which substitutents and where they are placed on the ring can be considered the most critical aspect of benzene chemistry in general.

Effects of Different Substituents

Depending on the type of substituent, atoms or groups of atoms may serve to make the benzene ring either more reactive or less reactive. If the atom or group makes the ring more reactive, it is called activating, and if less, then it is called deactivating.

Generally, the terms activating and deactivating are in terms of the reactions that fall into the category of Electrophilic Aromatic Substitution (EAS). These are the most common forms of reactions with aromatic rings. Aromatic rings can undergo other types of reactions, however, and in the case of Nucleophilic Aromatic Substitution, the activating and deactivating nature of substituents on the rings is reversed. In EAS, a hydroxyl groups is strongly activating, but in Nucleophilic Aromatic Substitution, a hydroxyl group is strongly deactivating. But since EAS is the most common reaction with aromatic rings, when discussing activation and deactivation, it's normally done in terms of the EAS.

In addition to activating or deactivating, all groups and/or substituent atoms on a benzene ring are directing. An atom or group may encourage additional atoms or groups to add or not to add to certain other carbons in relation to the carbon connected to the directing group. This concept will be further discussed in the next chapter, but when memorizing the groups below it is helpful to also memorize whether it is O (ortho), M (meta) or P (para)-directing.

Another factor that heavily influences direction, however, is steric hindrance. If, for example, you have a tert-butyl substituent on the ring, despite the fact that it is ortho/para directing, the ortho positions will be largely blocked by the tert-butyl group and thus nearly all the product would be para.

Activating Substituents

Activating substituents make benzene either slightly more reactive or very much more reactive, depending on the group or atom in question. In general, if one of the major heteroatoms (nitrogen or oxygen) is directly attached to the carbon ring then the result is probably activation. This is merely a rule of thumb, and many exceptions exist, so it is best to memorize the groups listed below instead of counting on a quick and dirty rule of thumb.

Group Strength Directing

-NH2, -NHR, -NRR very strong ortho/para

-OH, -O- very strong ortho/para

-NHCOCH3, -NHCOR strong ortho/para

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-OCH3, -OR strong ortho/para

-CH3, -C2H5, -R weak ortho/para

-C6H5 very weak ortho/para

Deactivating Substituents

A deactivating group is a functional group attached to a benzene molecule that removes electron density from the benzene ring, making electrophilic aromatic substitution reactions slower and more difficult than they would be on benzene alone. As discussed above for activating groups, deactivating groups may also determine the positions (relative to themselves) on the benzene ring where substitutions take place, so each deactivating group is listed below along with its directing characteristic.

Group Strength Directing

-NO2 very strong meta

-NR3+ very strong meta

-CF3, CCl3 very strong meta

-CN strong meta

-SO3H strong meta

-CO2H, -CO2R strong meta

-COH, -COR strong meta

-F weak ortho/para

-Cl weak ortho/para

-Br weak ortho/para

Activation vs. Deactivation and ortho/para vs. meta directing

So why are some substituents activating or deactivating? Why are some meta directing and others ortho/para directing? From the above tables, it seems pretty clear there's a relationship.

There are primarily two effects that substituents impart on the ring that affect these features:

1. Resonance effects 2. Inductive effects

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Resonance Effects

Let's first look at resonance effects. Resonance effects are the ability or inability of a substituent to provide electrons to the ring and enhance its resonance stability. To see this, we must first get a basic understanding of the mechanism of Electrophilic Aromatic Subsitution. We'll discuss EAS in more detail in the next section, but some basics are called for here.

As you can see in the image above, the electrophile is attacked by pi electrons in the ring. The same carbon is now bonded to both the hydrogen that was bonded to it and the electrophile. This in turn creates a carbocation on the adjacent carbon, making the ring non-aromatic. But aromatic rings like to remain aromatic. The nucleophile which was previously bonded to the electrophile now attacks the hydrogen, abstracting it from the ring and allowing the pi-bond to re-form and returning the ring to its aromatic nature.

As we've seen before in some other reactions, when a carbocation is created as an intermediate, stability of that carbocation is crucial to the reaction. This is the case in Electrophilic Aromatic Subsitution as well.

So what is the effect of substituents on the ring?

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Let's look at the situation above. In this case we have Phenol, a benzene ring with an -OH (hydroxyl) group attached. When we nitrate the ring with nitric acid in sulfuric acid (a reaction we'll discuss in the next section), a nitro group is attached to the benzene ring.

There are 3 possible places for the nitro group to attach: An ortho, meta, or para position. To understand the stability of the carbocation, we need to look at the resonance structures for a given attack and see what the results are.

The first resonance structure of the ortho attack results in a positive charge on the carbon with the hydroxyl group. This happens to be the most stable of the 3 resonance structures for an ortho attack because the two negative electron pairs in the oxygen act to stabilize the positive charge on the carbon. The other two resonance forms leave a carbon with a hydrogen attached, to hold the positive charge. Hydrogen can do nothing to stabilize the charge and thus, these are less stable forms.

In the para attack situation, notice that the second resonance form also puts a positive charge on the carbon with the hydroxyl group. This provides for stability just as it does in the case of an ortho attack and thus, the middle resonance form is very stable.

Finally, in the meta attack situation, all of the resonance forms result in a positive charge on a carbon with only a hydrogen attached. None of these is stable, and thus, meta attack with a hydroxyl group attached, is a very small percentage of the product.

So the electron pairs in the oxygen act to stabilize the ortho and para attacks.

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Inductive Effects

Now let's look at the inductive effects of deactivating substituents. Let's imagine that, instead of a hydroxyl group, we instead have a carbonyl group attached to the ring in its place. When a carbonyl is attached, the ring is bonded to a carbon which in turn, is double-bonded to an oxygen, the double-bonded oxygen is withdrawing electrons and this inductive effect is felt on the ring, strongly deactivating its pi-bond nature and putting a positive dipole on the carbon. Looking at the resonance structures, this carbon, which already has some positive nature is now given the added resonance of a positive charge, in the case of ortho and para attacks. Positive plus positive equals more positive and thus, less stable. There's no negative charge or negative electron pair to stabilize this positive charge.

So in this case, not only is the entire ring less activated, but the ortho and para attacks result in much more unstable carbocation resonance forms. Hence, meta is the preferred position, but the overall reaction is less active than plain benzene.

Halides as the Exception

Notice that in the list of activating vs. deactivating substituents, the activating ones are all ortho/para directing. In the deactivating substituents, all but the halides, are meta directing. Why are halides an exception?

Halides are more electronegative than carbon and thus they put a positive dipole on the carbon they're attached to and thus deactivate the ring. But halides also have a bunch of electrons in their outer shell to share with the ring, making the resonance structures with ortho and para attacks relatively more stable than the meta attack resonance forms. This means that, though halides do deactivate the ring to some extent, they are still ortho/para directing.

Detailed Effects of Substituents

We've discussed some generalities about the effects of substituents and even some specifics about certain ones, but let's look more closely at the substituents and try to understand the details of what makes them activating vs. deactivating.

-NH2, -NHR, and -NRR are all very strongly activating. Though nitrogen is more electronegative than carbon, its ability to share a pair of electrons greatly outweighs its electron withdrawing effect.

-OH and -O- is similar in that it is even more electronegative than nitrogen, but it has two pairs of electrons to share, which also greatly outweighs its electon withdrawing effect.

-NHCOCH3 and -NHCOR are also strongly activating, but the inductive effect of the double-bonded oxygen acts to make the nitrogen more electron withdrawing, so they're not quite as activating as the other -N subsituents above.

-OCH3 and -OR are also still strongly activating, but less so, because the electron density is shared on both sides of the oxygen.

-CH3 and -R in general provide some electron density sharing, but not nearly as much as a pair of electrons. Thus their effect is only weakly felt.

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For deactivating groups we have:

-NO2, or nitro and -NR3+. The nitro group is very strongly deactivating because of its resonance

structure. The nitro group has two resonance forms: O=N+-O- and O--N+=O. Both of these forms leave a full positive charge on the nitrogen making it completely unable to help stabilize the positive carbocation intermediate. The same applies to -NR3

+.

-CF3 and -CCl3 both have an inductive electronegative effect of 3 halides, but with no electrons to share with the ring, leaving them also very strongly deactivating.

-CN has a triple bond between the carbon and nitrogen with a resonance form of a double bond between the carbon and nitrogen and a positive charge on the carbon, meaning that between the electronegativity of the nitrogen and positively charged carbon in the resonance form, it destabilizes the carbocation and offer no electrons to the ring.

-SO3, -COR, -CO2R - all of these have electronegative oxygens giving the carbon a positive partial charge and providing no electrons for stability on the ring.

-F, -Cl, -Br, all have a similar effect. They are electronegative and deactivate the ring, but have electrons to share that, to some degree, makes up for it, allowing the ortho/para direction. But to understand their effects better, you need to look at them in terms of their placement on the periodic chart. Florine is the most electronegative element and it's very small and thus very close to the hydrogen it's bonded to. This gives its electromagnetic influence a stronger deactivating character. Chlorine is less electronegative, but it's also larger and thus further away from the carbon, making it harder for it to share its electrons. And so on.

Polysubstituted Benzenes

Unsubstituted benzene is seldom encountered in nature or in the laboratory, and you will find in your studies that most often benzene rings are found as parts of other, more complicated molecules. In order for benzene to react in most situations, it gains or loses some functionality dependent on which functional groups are attached. Although the simplest case is to work with benzene that has only one functional group, it is also essential to understand the interactions and competitions between multiple functional groups attached to the same benzene ring.

When there is more than one substituent present on a benzene ring the spatial relationship betwen groups becomes important, which is why the arene substitution patterns ortho, meta and para were devised. For example three isomers exist for the molecule cresol because the methyl group and the hydroxyl group can be placed either next to each other (ortho), one position removed from each other (meta) or two positions removed from each other (para). Where each group attaches is most often a function of which order they were attached in, due to the activating/deactivating and directing activities of previously attached groups.

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Competition Between Functional Groups

When a ring has more than one functional group, the effects of the groups are combined and their total effect must be taken into account. In general, effects are summed. For example, toluene (methylbenzene) is weakly activated. But p-nitrotoluene has both a methyl group and a nitro group. The methyl group is weakly activating and the nitro is pretty strongly deactivating, so overall, the group is very deactivated. In terms of direction, however, both substitutents agree on the direction. The methyl group is ortho/para directing. The nitro group occupies the para position, so the methyl will now want just ortho direction. The nitro group is meta directing. The positions meta to the nitro are also ortho to the methyl, so this works out and further substituents will be almost entirely in the positions ortho to the methyl group.

If two functional groups disagree on direction, the more activating group is the one that controls direction. That is, if you had m-nitrotoluene, most of your product would tend to be ortho/para to the toluene and not meta to the nitro, despite the nitro having a stronger influence on overall activation.

Naming Conventions

When a benzene ring has more than one substituent group attached, the location of all of the groups not directly attached to carbon number one must be explicitly declared. This is done by listing the number of the carbon atom where the group is attached, followed by a hyphen and the group's name. The carbon atoms of the benzene ring should be numbered in order of previously established precedence, i.e., a bromine would take precedence over a nitro group, which itself would take precedence over an alcohol or alkane group. The names of the groups should be listed in alphabetical order, i.e. "2-methyl-5-nitrobenzaldehyde."

. Sintesa alkena

H2Oa. RCH2CH2X + KOH RCH=CH2+ KX + H2Ob. RCHOH-CH3 + H2SO4 RCH=CH2 + H2O

c. RCHXCH2X + Zn RCH=CH2 + ZnX2 H2O

d. R-CH = CH2 + Hg(OCOCH3)2 R-CH = CH2 + NaBH4 R-CH = CH3 25 oC OH HgOCOCH3 OH

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Alkuna

Pemberian nama alkuna berdasarkan nama homolog alkana dimana akhiran ana diganti dengan

una. Contohnya

HC CH etuna

Alkuna alifatik

RC CH

Senyawa Nama Senyawa Nama Senyawa NamaCH4 Metuna C34H44 tetratriakontuna C67H136 heptaHeksa kontunaC2H6 Etuna C35H46 pentatriakontuna C68H138 oktaHeksa kontunaC3H8 Propuna C36H48 heksatriakontuna C69H140 nonaHeksa kontunaC4H10 Butuna C37H50 heptatriakontuna C70H142 HeptakontunaC5H12 Pentana C38H52 oktatriakontuna C71H144 henHeptakontunaC6H14 Heksuna C39H54 nonatriakontuna C72H146 DoHeptakontunaC7H16 Heptuna C40H56 Tetrakontuna C73H148 triHeptakontanaC8H18 Oktuna C41H58 hentetrakontuna C74H150 tetraHeptakontunaC9H20 Nonuna C42H60 Dotetrakontuna C75H152 pentaHeptakontunaC10H22 Dekuna C43H62 Tritetrakontuna C76H154 heksaHeptakontanaC11H24 Undekuna C44H64 tetratetrakontuna C77H156 heptaHeptakontunaC12H26 Dodekuna C45H66 pentatetrakontuna C78H158 oktaHeptakontunaC13H28 Tridekuna C46H68 heksatetrakontuna C79H160 nonaHeptakontunaC14H30 Tetradekuna C47H70 heptatetrakontuna C80H162 OktakontunaC15H32 Pentadekuna C48H72 oktatetrakontuna C81H164 henOktakontunaC16H34 Heksadekuna C49H74 nonatetrakontuna C82H166 doOktakontunaC17H36 Heptadekuna C50H102 Pentakontuna C83H168 triOktakontunaC18H38 Oktadekuna C51H104 Henpentakontuna C84H170 tetraOktakontunaC19H40 Nonadekuna C52H106 dopentakontuna C85H172 pentaOktakontunaC20H42 Eikosuna C53H108 tripentakontuna C86H174 heksaOktakontunaC21H44 Heneikosuna C54H110 tetrapentakontuna C87H176 heptaOktakontunaC22H46 Dokosuna C55H112 pentapentakontuna C88H178 oktaOktakontunaC23H48 Trikosuna C56H114 heksapentakontuna C89H180 nonaOktakontunaC24H50 Tetrakosuna C57H116 heptapentakontuna C90H182 NonakontunaC25H52 Pentakosuna C58H118 Oktapentakontuna C91H184 henNonakontunaC26H54 Heksakosuna C59H120 nonapentakontuna C92H186 doNonakontunaC27H56 Heptakosuna C60H122 Heksa kontana C93H188 triNonakontunaC28H58 Oktakosuna C61H124 HenHeksa kontuna C94H190 tetraNonakontunaC29H60 Nonakosuna C62H126 doHeksa kontuna C95H192 pentaNonakontunaC30H62 Triakontuna C63H128 triHeksa kontuna C96H194 heksaNonakontunaC31H64 Hentriakontuna C64H130 tetraHeksa kontuna C97H196 HeptaNonakontunaC32H66 Dotriakontuna C65H132 pentaHeksa kontuna C98H198 oktaNonakontunaC33H68 Tritriakontuna C66H134 heksaHeksa kontuna C99H200 nonaNonakontunaC100H202 Hektuna C400H802 Tetraktuna C700H1402 HeptaktunaC200H402 Diktuna C500H1002 Pentaktuna C800H1602 OktaktunaC300H6002 Triktuna C600H12002 Heksaktuna C900H1802 NonaktunaC1000H2002 kiliuna C4000H8002 Tetraliuna C7000H14002 HeptaliunaC2000H4002 Diliuna C500H10002 Pentaliuna C8000H16002 OktaliunaC3000H6002 Triliuna C3000H6002 Heksaliuna C9000H18002 Nonaliuna

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Alkapoliuna

R(C CH)n

Contohnya :

HC CH-HC CH Butadiuna

Sintesa Alkunasintesa alkuna dalam Industri

a. CH4 + 3H2 HC CH b. CH4 + O2 HC CH c. CaC2 + H2O HC CH + Ca(OH)2

Sintesa alkuna di laboratorium

d. RCHXCH2X + KNH2 R-C CH e. RCX2CH2X + Zn R-C CH

The triple carbon bonds is formed in alkenes, due to the absence of hydrogens, thus allowing carbon bonds to become stronger, due to the nucleus central force which pulls in nearby atoms

<< Alkenes |Alkynes| Dienes >>

Alkynes are hydrocarbons containing carbon-carbon triple bond. They exhibit neither geometric nor optical isomerism. The simplest alkyne is ethyne (HCCH), commonly known as acetylene, as shown at right.

Multiple Bonds Between Carbon Atoms

As you know from studying alkenes, atoms do not always bond with only one pair of electrons. In alkenes (as well in other organic and inorganic molecules) pairs of atoms can share between themselves more than just a single pair of electrons. Alkynes take this sharing a step further than alkenes, sharing three electron pairs between carbons instead of just two.

Two π Bonds

As you should know already, carbon is generally found in a tetravalent state - it forms four covalent bonds with other atoms. As you know from the section on alkenes, all four bonds are not necessarily to different atoms, because carbon atoms can double-bond to one another. What this does is create the appearance of only being bound to three other atoms, but in actuality four bonds exist.

Alkenes are molecules that consist of carbon and hydrogen atoms where one or more pairs of carbon atoms participate in a double bond, which consists of one sigma (σ) and one pi (π) bond.

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Alkynes are also molecules consisting of carbon and hydrogen atoms, but instead of forming a double bond with only one sigma (σ) and one pi (π) bond, the alkyne has at least one pair of carbon atoms who have a σ and two π bonds -- a triple bond.

The carbon-carbon triple bond, then, is a bond in which the carbon atoms share an s and two p orbitals to form just one σ and two π bonds between them. This results in a linear molecule with a bond angle of about 180 ﾟ. Since we know that double bonds are shorter than single covalent bonds, it would be logical to predict that the triple bond would be shorter still, and this is, in fact, the case. The triple bond’s length, 1.20Ǎ, is shorter than that of ethane and ethene’s 1.54 and 1.34 angstroms, respectively, but the difference between the triple and double bonds is slightly less than the difference between the single and double bonds.

The chemistry is very similar to alkenes in that both are formed by elimination reactions, and the major chemical reactions that alkynes undergo are addition type reactions.

Index Of Hydrogen Deficiency

If we compare the general molecular formulas for the Alkane, Alkene, and Alkyne families as well as the Cycloalkane and cycloalkene families we see the following relationship:

Family Molecular Formula

Alkane CnH2n+2

Alkene CnH2n

Cycloalkane CnH2n

Alkyne CnH2n-2

Cycloalkene CnH2n-2

We see that for a ring structure or a double bond there is a difference of two hydrogens compared to the alkane structure with the same number of carbons. If there is a ring + double bond (cycloalkene) or a triple bond (alkyne) then the difference is four hydrogens compared to the alkane with the same number of carbons. We say that the Index of Hydrogen Deficiency is equal to the number of pairs of Hydrogens that must be taken away from the alkane to get the same molecular formula of the compound under investigation. Every π-bond in the molecule increases the index by one. Any ring structure increases the index by one. Here is a list of possibilities:

Per molecule Index of Hydrogen Deficiency

One double bond 1

1 ring 1

1 double bond and 1 ring 2

2 double bonds 2

1 triple bond 2

1 triple bond + 1 double bond 3

3 double bonds 3

2 double bonds + 1 ring 3

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2 triple bonds 4

4 double bonds 4

Just remember that double bonds have 1 π bond, triple bonds have 2 π bonds and each π bond is an index of 1. We can use the index and the molecular formula to identify possibilities as to the exact nature of the molecule. For example, determine the molecular formula and speculate on what kind of Pi bonding and/or ring structure the molecules would have if the Index was given to be 3 and it is a 6 carbon hydrocarbon.

Identify the Alkane molecular formula for six carbons. For n = 6 we would have CnH2n+2. That would be C6H14.

Since an index of 3 means that there are 3 pairs(2) of hydrogen atoms less in the compound compared with the alkane we determined in step 1, then we would have C6H14-6 or C6H8.

In speculating as to what the bonding and structure could be with an index of 3 that could mean:

o Three double bonds in a non-cyclic structure like hexatriene o Two double bonds in a ring structure like a cyclohexadiene o One triple bond and one double bond in a non-cyclic structure

Clearly the answer cannot be determined from the formula alone, but the formula will give important clues as to a molecule's structure.

Cycloalkynes

Cycloalkynes are seldom encountered, and are not stable in small rings due to angle strain. Cyclooctyne has been isolated, but is very reactive, and will polymerize with itself quickly. Cyclononyne is the smallest stable cycloalkyne.

Benzyne is another cycloalkyne that has been proposed as an intermediate for elimination-addition reactions of benzene.

Preparation

In order to synthesize alkynes, one generally starts with a vicinal or geminal dihalide (an alkane with two halogen atoms attached either next to one another or across from one another). Adding sodium amide (NaNH2) removes the halogens with regiochemistry subject to Zaitsev's Rule, resulting in a carbon-carbon triple bond due to the loss of both halogens as well as two hydrogen atoms from the starting molecule. This is called a double dehydrohalogenation.

The starting compound is a salt already containing a carbon-carbon double bond. One such compound is maleic acid. Mechanism is similar to that of formation of ethane using kolbe's electrolysis.

CH-COONa| (sodium maleate) (maleic acid)CH-COONa

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At Anode: At cathode:CH-COO- 2Na+ + 2e- -> 2Na||CH-COO- 2Na + H20 -> 2NaOH + H2

-2e- ->

CH-COO* CH* CH|| -> -2CO2 -> || -> |||CH-COO* CH* CH(free radical formation)

In this manner, alkyne is obtained at anode, while NaOH is formed at cathode and hydrogen gas is liberated.

Vicinal dihalides may be converted into alkynes by using extreme conditions such as sodium amide NaNH2 typically at 150°C or molten/fused potassium hydroxide KOH typically at 200°C.

From Calcium carbide

Calcium carbide is the compound CaC2, which consists of calcium ions (Ca2+) and acetylide ions, C2

2-. It is synthesized from lime and coke in the following reaction:

CaO + 3C → CaC2 + CO

This reaction is very endothermic and requires a temperature of 2000o C. For this reason it is produced in an electrical arc furnace.

Calcium carbide may formally be considered a derivative of acetylene, an extremely weak acid (though not as weak as ammonia). The double deprotonation means that the carbide ion has very high energy. Instant hydrolysis occurs when water is added to calcium carbide, yielding acetylene gas.

From alkyl or aryl halides

Properties

Physical properties

Most alkynes are less dense than water (they float on top of water), but there are a few exceptions.

Chemical properties

Liquid alkynes are non-polar solvents, immiscible with water. Alkynes are, however, more polar than alkanes or alkenes, as a result of the electron density near the triple bond.

Alkynes with a low ratio of hydrogen atoms to carbon atoms are highly combustible. Carbon-carbon triple bonds are highly reactive and easily broken or converted to double or single bonds.

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Triple bonds store large amounts of chemical energy and thus are highly exothermic when broken. The heat released can cause rapid expansion, so care must be taken when working with alkynes such as acetylene.

One synthetically important property of terminal alkynes is the acidity of their protons. Whereas the protons in alkanes have pKa's around 60 and alkene protons have pKa's in the mid-40's, terminal alkynes have pKa's of about 25. Substitution of the alkyne can reduce the pKa of the alkyne even further; for example, PhCCH has a pKa around 23, and Me3SiCCH has a pKa around 19. The acidity of alkynes allows them easily to be deprotonated by sufficiently strong bases, such as butyllithium BuLi or the amide ion NH2

-. More acidic alkynes such as PhCCH can even be deprotonated by alkoxide bases under the right conditions.

Reactions

Alkynes can be hydrated into either a ketone or an aldehyde form. A (Markovnikov) ketone can be created from an alkyne using a solution of aqueous sulfuric acid (H2O/H2SO4) and HgSO4, whereas the anti-Markovnikov aldehyde product requires different reagents and is a multi-step process.

Hydrohalogenation of Alkynes

Alkynes react very quickly and to completion with hydrogen halides. Addition is anti, and follows the Markovnikov Rule.

RCCH + H-Br (1 equiv) --> RCBr=CH2

RCCH + H-Br (2 equivs) --> RCBr2CH3

Adding a halide acid such as HCl or HBr to an alkyne can create a geminal dihalide via a Markovnikov process, but adding HBr in the presence of peroxides results in the Anti-Markovnikov alkenyl bromide product.

Halogenation of Alkynes

Adding diatomic halogen molecules such as Br2 or Cl2 results in 1,2-dihaloalkene, or, if the halogen is added in excess, a 1,1,2,2-tetrahaloalkane.

Adding H2O along with the diatomic halide results in a halohydrin addition and an α-halo ketone.

Combustion

Alkynes burn in air with a sooty, yellow flame, like alkanes. Alkenes also burn yellow, while alkanes burn with blue flames. Acetylene burns with large amounts of heat, and is used in oxyacetylene torches for welding metals together, for example, in the superstructures of skyscrapers.

2 C2H2 + 5 O2 --> 4 CO2 + 2 H2O

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Reduction

Alkynes can be hydrogenated by adding H2 with a metallic catalyst, such as palladium-carbon or platinum or nickel, which results in a both of the alkyne carbons becoming fully saturated. If Lindlar's catalyst is used instead, the alkyne hydrogenates to a Z enantiomer alkene, and if an alkali metal in an ammonia solution is used for hydrogenating the alkyne, an E enantiomer alkene is the result.

Complete Hydrogenation of Alkynes

As mentioned above, alkynes are reduced to alkanes in the presence of an active metal catalyst, such as Pt, Pd, Rh, or Ni in the presence of heat and pressure.

RCCR' + 2 H2 (Pt cat.)--> RCH2CH2R'

Syn-Hydrogenation of an Alkyne

There are two kinds of addition type reactions where a π-bond is broken and atoms are added to the molecule. If the atoms are added on the same side of the molecule then the addition is said to be a "syn" addition. If the added atoms are added on opposite sides of the molecule then the addition is said to be an "anti" addition. Hydrogen atoms can be added to an alkyne on a one mole to one mole ratio to get an alkene where the hydrogen atoms have been added on the same side of the molecule. Isotopic identification allows chemists to determine when this syn-hydrogenation has occurred.

As mentioned above, alkynes can be reduced to cis-alkenes by hydrogen in the presence of Lindlar Pd, i.e. palladium doped with CaSO4 or BaSO4.

RCCR + H2 cis-RCH=CHR

Anti-Hydrogenation of an Alkyne

In regards to the syn-hydrogenation, anti is hydrogenation when one hydrogen is added from the top of the pi bond and the other is added from the bottom.

Anion formation

Because of the acidity of the protons of terminal alkynes, they are easily converted into alkynyl anions in high yield by strong bases.

Examples

RCCH + NaNH2 -> RCCNa + NH3 C4H9Li + RCCH -> C4H10 +RCCLi

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Alkynes are stronger bases than water, and acetylene (ethyne) is produced in a science classroom reaction of calcium carbide with water.

CaC2 + 2 H20 --> Ca(OH)2 + C2H2

Alkynyl anions are useful in lengthening carbon chains. They react by nucleophilic substitution with alkyl halides.

R-Cl + R'CCNa --> RCCR' + NaCl

The product of this reaction can be reduced to an alkane with hydrogen and a platinum or rhodium catalyst, or an alkene with Lindlar palladium.

Alkil halide

Halogens (Alkyl Halides)Main article: Halogens

Halogen functional groups are prefixed with the bonding position and take the form fluoro-, chloro-, bromo-, iodo-, etc., depending on the halogen. Multiple groups are dichloro-, trichloro-, etc, and dissimilar groups are ordered alphabetically as before. For example, CHCl3 (chloroform) is trichloromethane. The anesthetic Halothane (CF3CHBrCl) is 2-bromo-2-chloro-1,1,1-trifluoroethane.

5.4.1. Pemberian nama alkyl halida

Senyawa Nama Senyawa Nama Senyawa NamaCH4 Metil halida C34H44 Tetratriakontil halida C67H136 heptaHeksa kontil

halidaC2H6 Etil halida C35H46 Pentatriakontil halida C68H138 oktaHeksa kontil halidaC3H8 Propil halida C36H48 Heksatriakontil halide C69H140 nonaHeksa kontanaC4H10 Butil halida C37H50 Heptatriakontil halide C70H142 Heptakontil halidaC5H12 Pentil halida C38H52 Oktatriakontil halida C71H144 henHeptakontil halideC6H14 Heksil halida C39H54 Nonatriakontil halida C72H146 DoHeptakontil halideC7H16 Heptil halide C40H56 Tetrakontil halida C73H148 triHeptakontil halideC8H18 Oktil halide C41H58 Hentetrakontil halida C74H150 tetraHeptakontil halideC9H20 Nonil halide C42H60 Dotetrakontil halide C75H152 pentaHeptakontil halide

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C10H22 Dekil halide C43H62 Tritetrakontil halida C76H154 heksaHeptakontil halideC11H24 Undekil halide C44H64 Tetratetrakontil

halidaC77H156 heptaHeptakontil halide

C12H26 Dodekil halide C45H66 Pentatetrakontil halida

C78H158 oktaHeptakontil halide

C13H28 Tridekil halide C46H68 Heksatetrakontil halida

C79H160 nonaHeptakontil halide

C14H30 Tetradekil halide C47H70 Heptatetrakontil halida

C80H162 Oktakontil halide

C15H32 Pentadekil halide C48H72 Oktatetrakontil halida C81H164 henOktakontil halideC16H34 Heksadekil

halideC49H74 Nonatetrakontil

halideC82H166 doOktakontil halida

C17H36 Heptadekil halide C50H102 Pentakontil halide C83H168 triOktakontil halideC18H38 Oktadekil halide C51H104 Henpentakontil halide C84H170 tetraOktakontil halideC19H40 Nonadekil halide C52H106 Dopentakontil halide C85H172 pentaOktakontil halideC20H42 Eikosil halide C53H108 Tripentakontil halide C86H174 heksaOktakontil halideC21H44 Heneikosil halide C54H110 Tetrapentakontil

halideC87H176 heptaOktakontil halide

C22H46 Dokosil halide C55H112 Pentapentakontil halida

C88H178 oktaOktakontil halide

C23H48 Trikosil halide C56H114 Heksapentakontil halida

C89H180 nonaOktakontil halide

C24H50 Tetrakosil halide C57H116 Heptapentakontil halida

C90H182 Nonakontil halide

C25H52 Pentakosil halide C58H118 Oktapentakontil halida

C91H184 henNonakontil halide

C26H54 Heksakosil halide C59H120 Nonapentakontil halida

C92H186 doNonakontil halide

C27H56 Heptakosil halide C60H122 Heksa kontil halide C93H188 triNonakontil halideC28H58 Oktakosil halide C61H124 HenHeksa kontil

halideC94H190 tetraNonakontil halide

C29H60 Nonakosil halide C62H126 doHeksa kontil halide C95H192 pentaNonakontil halideC30H62 Triakontil halide C63H128 triHeksa kontil halide C96H194 heksaNonakontil halideC31H64 Hentriakontil

halideC64H130 tetraHeksa kontil

halideC97H196 HeptaNonakontil halide

C32H66 Dotriakontil halide

C65H132 pentaHeksa kontil halide

C98H198 oktaNonakontil halide

C33H68 Tritriakontil halida

C66H134 heksaHeksa kontil C99H200 nonaNonakontil halide

C100H202 Hektil halida C400H802 Tetrahektil halide C700H1402 Heptahektil halideC200H402 Dohektil halide C500H1002 Pentahektil halide C800H1602 Oktahektil halideC300H6002 Trihektil halide C600H12002 Heksahektil halide C900H1802 Nonahektil halideC1000H2002 Kiliil halide C400H8002 Tetraliil halide C700H14002 Heptaliil halideC2000H4002 Diliil halide C500H10002 Penliil halide C800H16002 Oktaliil halideC3000H6002 Triliil halida C600H1202 Heksaliil halide C900H18002 Nonaliil halide

5.4.2. Sintesa alkil halida

a. C6H5CH3 + X2 C6H5CH2X + HXb. (CH3)3CCH3 + X2 (CH3)3CCH2X + HX

c. R-CH2CH2OH + NaX + H2SO4 R-CH2CH2X + Na2SO4 + H2O

d. R-CH2CH2OH + HX R-CH2CH2X + H2O

e. R-CH2CH2OH + SOX2 R-CH2CH2X + H2SO4

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f. R-CH2CH2OH + PX3 R-CH2CH2X + H3PO4

g. RHC=CH2 + HX R-CH2CH2X

5.4.2. Reaksi-reaksi alkil halide

Alkanol

Alcohols (R-OH) take the suffix "-ol" with an infix numerical bonding position: CH3CH2CH2OH is propan-1-ol. The suffixes -diol, -triol, -tetraol, etc., are used for multiple -OH groups: Ethylene glycol CH2OHCH2OH is ethane-1,2-diol.

If higher precedence functional groups are present (see order of precedence, below), the prefix "hydroxy" is used with the bonding position: CH3CHOHCOOH is 2-hydroxypropanoic acid.

Alcohols (R-OH) take the suffix "-ol" with an infix numerical bonding position: CH3CH2CH2OH is propan-1-ol. The suffixes -diol, -triol, -tetraol, etc., are used for multiple -OH groups: Ethylene glycol CH2OHCH2OH is ethane-1,2-diol.

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If higher precedence functional groups are present (see order of precedence, below), the prefix "hydroxy" is used with the bonding position: CH3CHOHCOOH is 2-hydroxypropanoic acid.

Pemberian nama deret homolog alkanol

Senyawa Nama Senyawa Nama Senyawa NamaCH4 Metanol C34H44 Tetratriakontanol C67H136 heptaHeksa kontanolC2H6 Etanol C35H46 Pentatriakontanol C68H138 oktaHeksa kontanolC3H8 Propanol C36H48 Heksatriakontanol C69H140 nonaHeksa kontanolC4H10 Butanol C37H50 Heptatriakontanol C70H142 HeptakontanolC5H12 Pentanol C38H52 Oktatriakontanol C71H144 henHeptakontanolC6H14 Heksanol C39H54 Nonatriakontanol C72H146 DoHeptakontanolC7H16 Heptanol C40H56 Tetrakontanol C73H148 triHeptakontanolC8H18 Oktanol C41H58 Hentetrakontanol C74H150 tetraHeptakontanolC9H20 Nonanol C42H60 Dotetrakontanol C75H152 pentaHeptakontanolC10H22 Dekanol C43H62 Tritetrakontanol C76H154 heksaHeptakontanolC11H24 Undekanol C44H64 Tetratetrakontanol C77H156 heptaHeptakontanolC12H26 Dodekanol C45H66 Pentatetrakontanol C78H158 oktaHeptakontanolC13H28 Tridekanol C46H68 Heksatetrakontanol C79H160 nonaHeptakontanolC14H30 Tetradekanol C47H70 Heptatetrakontanol C80H162 OktakontanolC15H32 Pentadekanol C48H72 Oktatetrakontanol C81H164 henOktakontanolC16H34 Heksadekanol C49H74 Nonatetrakontanol C82H166 doOktakontanolC17H36 Heptadekanol C50H102 Pentakontanol C83H168 triOktakontanolC18H38 Oktadekanol C51H104 Henpentakontanol C84H170 tetraOktakontanolC19H40 Nonadekanol C52H106 Dopentakontanol C85H172 pentaOktakontanolC20H42 Eikosanol C53H108 Tripentakontanol C86H174 heksaOktakontanolC21H44 Heneikosanol C54H110 Tetrapentakontanol C87H176 heptaOktakontanolC22H46 Dokosanol C55H112 Pentapentakontanol C88H178 oktaOktakontanolC23H48 Trikosanol C56H114 Heksapentakontanol C89H180 nonaOktakontanolC24H50 Tetrakosanol C57H116 Heptapentakontanol C90H182 NonakontanolC25H52 Pentakosanol C58H118 Oktapentakontanol C91H184 henNonakontanolC26H54 Heksakosanol C59H120 Nonapentakontanol C92H186 doNonakontanolC27H56 Heptakosanol C60H122 Heksa kontanol C93H188 triNonakontanolC28H58 Oktakosanol C61H124 HenHeksa kontanol C94H190 tetraNonakontanolC29H60 Nonakosanol C62H126 doHeksa kontanol C95H192 pentaNonakontanolC30H62 Triakontanol C63H128 triHeksa kontanol C96H194 heksaNonakontanolC31H64 Hentriakontanol C64H130 tetraHeksa kontanol C97H196 HeptaNonakontanolC32H66 Dotriakontanol C65H132 pentaHeksa kontanol C98H198 oktaNonakontanolC33H68 Tritriakontanol C66H134 heksaHeksa kontanol C99H200 nonaNonakontanolC100H202 Hektanol C400H802 Tetrahektanol C700H1402 HeptahektanolC200H402 Dohektanol C500H1002 Pentahektanol C800H1602 OktahektanolC300H6002 Trihektanol C600H12002 Heksahektanol C900H1802 NonahektanolC1000H2002 Kilianol C400H8002 Tetralianol C700H14002 HeptalianolC2000H4002 Dilianatanol C500H10002 Pentaliaanol C800H16002 OktalianolC3000H6002 Trilianol C600H1202 Heksalianol C900H18002 Nonalianol

Sintesa alkanol

a. RX + OH- ROH + X-

b. C = C + H2O CH – COH

c. R-CH = CH2 + B2H6 (RCH2– CH2)3-B+ H2O2 RCH2– CH2OH OH-

76

H2O d. R-CH = CH2 + Hg(OCOCH3)2 R-CH - CH2 + NaBH4 R-CH-CH3 25 oC OH HgOCOCH3 OH

H R R e. RMgX + R-C= O RCHOMgX + H2O RCHOH + MgXOH

g. LiAlH4 + RCHO RCH2OH

Reaksi-reaksi alkanol

Alkoksi alkana

Main article: Ethers

Ethers (R-O-R) consist of an oxygen atom between the two attached carbon chains. The shorter of the two chains becomes the first part of the name with the -ane suffix changed to -oxy, and the longer alkane chain become the suffix of the name of the ether. Thus CH3OCH3 is methoxymethane, and CH3OCH2CH3 is methoxyethane (not ethoxymethane). If the oxygen is not attached to the end of the main alkane chain, then the whole shorter alkyl-plus-ether group is treated as a side-chain and prefixed with its bonding position on the main chain. Thus CH3OCH(CH3)2 is 2-methoxypropane.

Senyawa Nama Senyawa Nama Senyawa NamaCH3O- Metoksi C34H44 tetratriakontoksi C67H136 heptaHeksa kontoksiC2H5O- Etoksi C35H46 pentatriakontoksi C68H138 oktaHeksa kontoksiC3H8 Propoksi C36H48 heksatriakontoksi C69H140 nonaHeksa kontoksiC4H10 Butoksi C37H50 heptatriakontoksi C70H142 HeptakontoksiC5H12 Pentoksi C38H52 oktatriakontoksi C71H144 henHeptakontoksiC6H14 Heksoksi C39H54 nonatriakontoksi C72H146 DoHeptakontoksiC7H16 Heptoksi C40H56 Tetrakontoksi C73H148 triHeptakontoksiC8H18 Oktoksi C41H58 hentetrakontoksi C74H150 tetraHeptakontoksiC9H20 Nonoksi C42H60 Dotetrakontoksi C75H152 pentaHeptakontoksiC10H22 Dekoksi C43H62 Tritetrakontoksi C76H154 heksaHeptakontoksiC11H24 Undekoksi C44H64 tetratetrakontoksi C77H156 heptaHeptakontoksiC12H26 Dodekoksi C45H66 pentatetrakontoksi C78H158 oktaHeptakontoksiC13H28 Tridekoksi C46H68 heksatetrakontoksi C79H160 nonaHeptakontoksiC14H30 Tetradekoksi C47H70 heptatetrakontoksi C80H162 OktakontoksiC15H32 Pentadekoksi C48H72 oktatetrakontoksi C81H164 henOktakontoksiC16H34 Heksadekoksi C49H74 nonatetrakontoksi C82H166 doOktakontoksiC17H36 Heptadekoksi C50H102 Pentakontoksi C83H168 triOktakontoksiC18H38 Oktadekoksi C51H104 Henpentakontoksi C84H170 tetraOktakontoksiC19H40 Nonadekoksi C52H106 Dopentakontoksi C85H172 pentaOktakontoksiC20H42 Eikosoksi C53H108 Tripentakontoksi C86H174 heksaOktakontoksiC21H44 Heneikosoksi C54H110 Tetrapentakontoksi C87H176 heptaOktakontosiC22H46 Dokosoksi C55H112 Pentapentakontoksi C88H178 oktaOktakontoksi

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C23H48 Trikosoksi C56H114 Heksapentakontoksi C89H180 nonaOktakontoksiC24H50 Tetrakosoksi C57H116 Heptapentakontoksi C90H182 NonakontoksiC25H52 Pentakosoksi C58H118 Oktapentakontoksi C91H184 henNonakontoksiC26H54 Heksakosoksi C59H120 Nonapentakontoksi C92H186 doNonakontoksiC27H56 Heptakosoksi C60H122 Heksa kontoksi C93H188 triNonakontoksiC28H58 Oktakosoksi C61H124 HenHeksa kontoksi C94H190 tetraNonakontoksiC29H60 Nonakosoksi C62H126 doHeksa kontoksi C95H192 pentaNonakontoksiC30H62 Triakontoksi C63H128 triHeksa kontoksi C96H194 heksaNonakontoksiC31H64 Hentriakontoksi C64H130 tetraHeksa kontoksi C97H196 HeptaNonakontoksiC32H66 Dotriakontoksi C65H132 pentaHeksa kontoksi C98H198 oktaNonakontoksiC33H68 Tritriakontoksi C66H134 heksaHeksa kontoksi C99H200 nonaNonakontoksiC100H202 Hektoksi C400H802 Tetrahektosi C700H1402 HeptahektoksiC200H402 Dohektoksi C500H1002 Pentahektoksi C800H1602 OktahektoksiC300H6002 Trihektoksi C600H12002 Heksahektosi C900H1802 NonahektoksiC1000H2002 Kilioksi C400H8002 Tetralioksi C700H14002 HeptaliokaiC2000H4002 Dilioksi C500H10002 Penlioksi C800H16002 OktalioksiC3000H6002 Trilioksi C600H1202 Heksalioksi C900H18002 Nonalioksi

Pemberian nama

Nama senyawa alkoksi alkana adalah nama homolog alkana, dimana nama alkana sebelum

atom oksigen akhiran nama alkana diganti dengan akhiran oksi dan nama homolog alkana

sesudah atom oksigen sesuai dengan homolog alkananya.

Contoh

H3C-CH2-CH2-O-CH2-CH3

Etoksi propanaSintesa alkoksi alkana

a. H3C-CH2OH + H2SO4 H3C-CH2-O-H2C-CH3 b. (H3C)2-CHCl + Ag2O . (H3C)2-CH-O-CH-(H3C)2

c. R-O-Na + R’Cl R-O-R’ + NaCl

BF3

d. C7H13OH + CH2N2 C7H13OCH3 + N2

e. C6H5OH + CH2N2 C6H5OCH3 + N2

f. R-CH = CH2 + Hg(OCOCF3)2 + R’OH R-CH - CH2 + NaBH4 OR HgOCOCF3

AlkanalMain article: Aldehydes

78

Aldehydes (R-CHO) take the suffix "-al".If other functional groups are present, the chain is numbered such that the aldehyde carbon is in the "1" position.

If a prefix form is required, "oxo-" is used (as for ketones), with the position number

indicating the end of a chain: CHOCH2COOH is 3-oxopropanoic acid. If the carbon in the

carbonyl group cannot be included in the attached chain (for instance in the case of cyclic

aldehydes), the prefix "formyl-" or the suffix "-carbaldehyde" is used: C6H11CHO is

cyclohexanecarbaldehyde. If a aldehyde is attached to a benzene and is the main functional

group, the suffix becomes benzaldehyde.

5.7.1. Pemberian nama alkanal

Nama alkanal berasal dari homolog alkana dengan mengganti akhiran a dengan al

Senyawa Nama Senyawa Nama Senyawa NamaCH4 Metanal C34H44 Tetratriakontanal C67H136 heptaHeksa kontanalC2H6 Etanal C35H46 Pentatriakontanal C68H138 oktaHeksa kontanalC3H8 Propanal C36H48 Heksatriakontanal C69H140 nonaHeksa kontanalC4H10 Butanal C37H50 Heptatriakontanal C70H142 HeptakontanalC5H12 Pentanal C38H52 Oktatriakontanal C71H144 henHeptakontanalC6H14 Heksanal C39H54 Nonatriakontanal C72H146 DoHeptakontanalC7H16 Heptanal C40H56 Tetrakontanal C73H148 triHeptakontanalC8H18 Oktanal C41H58 Hentetrakontanal C74H150 tetraHeptakontanalC9H20 Nonanal C42H60 Dotetrakontanal C75H152 pentaHeptakontanalC10H22 Dekanal C43H62 Tritetrakontanal C76H154 heksaHeptakontanalC11H24 Undekanal C44H64 Tetratetrakontanal C77H156 heptaHeptakontanalC12H26 Dodekanal C45H66 Pentatetrakontanal C78H158 oktaHeptakontanalC13H28 Tridekanal C46H68 Heksatetrakontanal C79H160 nonaHeptakontanalC14H30 Tetradekanal C47H70 Heptatetrakontanal C80H162 OktakontanalC15H32 Pentadekanal C48H72 Oktatetrakontanal C81H164 henOktakontanalC16H34 Heksadekanal C49H74 Nonatetrakontanal C82H166 doOktakontanalC17H36 Heptadekanal C50H102 Pentakontanal C83H168 triOktakontanalC18H38 Oktadekanal C51H104 Henpentakontanal C84H170 tetraOktakontanalC19H40 Nonadekanal C52H106 Dopentakontanal C85H172 pentaOktakontanalC20H42 Eikosanal C53H108 Tripentakontanal C86H174 heksaOktakontanalC21H44 Heneikosanal C54H110 Tetrapentakontanal C87H176 heptaOktakontanalC22H46 Dokosanal C55H112 pentapentakontanal C88H178 oktaOktakontanalC23H48 Trikosanal C56H114 Heksapentakontanal C89H180 nonaOktakontanal

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C24H50 Tetrakosanal C57H116 Heptapentakontanal C90H182 NonakontanalC25H52 Pentakosanal C58H118 Oktapentakontanal C91H184 henNonakontanalC26H54 Heksakosanal C59H120 Nonapentakontanal C92H186 doNonakontanalC27H56 Heptakosanal C60H122 Heksa kontanal C93H188 triNonakontanalC28H58 Oktakosanal C61H124 HenHeksa kontanal C94H190 tetraNonakontanalC29H60 Nonakosanal C62H126 doHeksa kontanal C95H192 pentaNonakontanalC30H62 Triakontanal C63H128 triHeksa kontanal C96H194 heksaNonakontanalC31H64 Hentriakontanal C64H130 tetraHeksa kontanal C97H196 HeptaNonakontanalC32H66 Dotriakontanal C65H132 pentaHeksa kontana C98H198 oktaNonakontanalC33H68 Tritriakontanal C66H134 heksaHeksa kontanal C99H200 nonaNonakontanalC100H202 Hektanal C400H802 Tetrahektanal C700H1402 HeptahektanalC200H402 Dohektanal C500H1002 Pentahektanal C800H1602 OktahektanalC300H6002 Trihektanal C600H12002 Heksahektanal C900H1802 NonahektanalC1000H2002 Kilianal C400H8002 Tetralianal C700H14002 HeptalianalC2000H4002 Dilianatanal C500H10002 Penliaanal C800H16002 OktalianalC3000H6002 Trilianal C600H1202 Heksalianal C900H18002 Nonalianal

5.7.2. Sintesa alkanal

a. RCH2OH + KMnO4 RC =O O H

b. H3C-(CH2)6I + CH3 - S - CH3 H3C- (CH2)5 C =O + H3C-S-CH3

H

c. Ar-CH3 + Cl2 Ar-CH-Cl2 + H2O ArCHO

d. RCOCl + LiAl{(CH3)3CO}3)2H R-CHO + LiCl + Al{(CH3)3CO}3)2

HCl, AlCl3

e. C6H5(CH3)2 + CO p-(CH3)2CHC6H4CHO CuCl

5.7.3. Reaksi-reaksi alkanal

Alkanon

Main article: Ketones

In general ketones (R-CO-R) take the suffix "-one" (pronounced own, not won) with an infix

position number: CH3CH2CH2COCH3 is pentan-2-one. if a higher precedence suffix is in use, the

prefix "oxo-" is used: CH3CH2CH2COCH2CHO is 3-oxohexanal.

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Pemberian nama alkanon

Nama alkanon berasal dari homolog alkana dengan mengganti akhiran a dengan on

Senyawa Nama Senyawa Nama Senyawa NamaCH4 Metan……. C34H44 Tetratriakontanon C67H136 heptaHeksa kontanonC2H6 Etan…….. C35H46 Pentatriakontanon C68H138 oktaHeksa kontanonC3H8 Propanon C36H48 heksatriakontanon C69H140 nonaHeksa kontanonC4H10 Butanon C37H50 Heptatriakontanon C70H142 HeptakontanonC5H12 Pentanon C38H52 Oktatriakontanon C71H144 henHeptakontanonC6H14 Heksanon C39H54 Nonatriakontanon C72H146 DoHeptakontanonC7H16 Heptanon C40H56 Tetrakontanon C73H148 triHeptakontanonC8H18 Oktanon C41H58 Hentetrakontanon C74H150 tetraHeptakontanonC9H20 Nonanon C42H60 Dotetrakontanon C75H152 pentaHeptakontanonC10H22 Dekanon C43H62 Tritetrakontanon C76H154 heksaHeptakontanonC11H24 Undekanon C44H64 Tetratetrakontanon C77H156 heptaHeptakontanonC12H26 Dodekanon C45H66 Pentatetrakontanon C78H158 oktaHeptakontanonC13H28 Tridekanon C46H68 Heksatetrakontanon C79H160 nonaHeptakontanonC14H30 Tetradekanon C47H70 Heptatetrakontanon C80H162 OktakontanonC15H32 Pentadekanon C48H72 Oktatetrakontanon C81H164 henOktakontanonC16H34 Heksadekanon C49H74 Nonatetrakontanon C82H166 doOktakontanonC17H36 Heptadekanon C50H102 Pentakontanon C83H168 triOktakontanonC18H38 Oktadekanon C51H104 Henpentakontanon C84H170 tetraOktakontanonC19H40 Nonadekanon C52H106 Dopentakontanon C85H172 pentaOktakontanonC20H42 Eikosanon C53H108 Tripentakontanon C86H174 heksaOktakontanonC21H44 Heneikosanon C54H110 Tetrapentakontanon C87H176 heptaOktakontanonC22H46 Dokosanon C55H112 Pentapentakontanon C88H178 oktaOktakontanonC23H48 Trikosanon C56H114 heksapentakontanon C89H180 nonaOktakontanonC24H50 Tetrakosanon C57H116 Heptapentakontanon C90H182 NonakontanonC25H52 Pentakosanon C58H118 Oktapentakontanon C91H184 henNonakontanonC26H54 Heksakosanon C59H120 Nonapentakontanon C92H186 doNonakontanonC27H56 Heptakosanon C60H122 Heksa kontanon C93H188 triNonakontanonC28H58 Oktakosanon C61H124 HenHeksa kontanon C94H190 tetraNonakontanonC29H60 Nonakosanon C62H126 doHeksa kontanon C95H192 pentaNonakontanonC30H62 Triakontanon C63H128 triHeksa kontanon C96H194 heksaNonakontanonC31H64 Hentriakontanon C64H130 tetraHeksa kontanon C97H196 HeptaNonakontanonC32H66 Dotriakontanon C65H132 pentaHeksa kontanon C98H198 oktaNonakontanonC33H68 Tritriakontanon C66H134 heksaHeksa kontanon C99H200 nonaNonakontanonC100H202 Hektanon C400H802 Tetrahektanon C700H1402 HeptahektanonC200H402 Dohektanon C500H1002 Pentahektanon C800H1602 OktahektanonC300H6002 Trihektanon C600H12002 Heksahektanon C900H1802 NonahektanonC1000H2002 Kilianon C400H8002 Tetralianon C700H14002 HeptalianonC2000H4002 Dilianatanon C500H10002 Penliaanon C800H16002 OktalianonC3000H6002 Trilianon C600H1202 Heksalianon C900H18002 Nonalianon

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Sintesa alkanon

a. R2CHOH + KMnO4 + 8 H+ R2C=O + Mn+2 + 4H2O + K+

AlCl3

b ArH + RCOCl ArCOR + HCl

O R O

c. R-CClCH = O + H2C=CHR (R-C-CH2– CHCl) + RCCH=CHR

O

d. R-ClC = O + R2Cd R-C-R + CdCl2

e. HOOC(CH2)nCOOH + BaO (CH2)n C=O + BaCO3 + H2O

CH3 CH3 CH3 O f. CrO3

+ B2H6 H3O+

3B

5.8.3. Reaksi-reaksi alkanon

Alkanoat

Main article: Carboxylic acids

In general carboxylic acids are named with the suffix -oic acid (etymologically a back-formation from benzoic acid). As for aldehydes, they take the "1" position on the parent chain, but do not have their position number indicated. For example, CH3CH2CH2CH2COOH (valeric acid) is named pentanoic acid. For common carboxylic acids some traditional names such as acetic acid are in such widespread use they are considered retained IUPAC names, although "systematic" names such as ethanoic acid are also acceptable. For carboxylic acids attached to a benzene ring such as Ph-COOH, these are named as benzoic acid or its derivatives.

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If there are multiple carboxyl groups on the same parent chain, the suffix "-carboxylic acid" can be used (as -dicarboxylic acid, -tricarboxylic acid, etc.). In these cases, the carbon in the carboxyl group does not count as being part of the main alkane chain. The same is true for the prefix form, "carboxyl-". Citric acid is one example; it is named 2-hydroxypropane- 1,2,3-tricarboxylic acid, rather than 2-carboxy, 2-hydroxypentanedioic acid.

Senyawa Nama Senyawa Nama Senyawa NamaCH4 Metanoat C34H44 tetratriakontanoat C67H136 heptaHeksa kontanoatC2H6 Etanoat C35H46 pentatriakontanoat C68H138 oktaHeksa kontanoatC3H8 Propanoat C36H48 heksatriakontanoat C69H140 nonaHeksa kontanoatC4H10 Butanoat C37H50 heptatriakontanoat C70H142 HeptakontanoatC5H12 Pentanoat C38H52 oktatriakontanoat C71H144 henHeptakontanoatC6H14 Heksanoat C39H54 nonatriakontanoat C72H146 DoHeptakontanoatC7H16 Heptanoat C40H56 Tetrakontanoat C73H148 triHeptakontanoatC8H18 Oktanoat C41H58 Hentetrakontanoat5 C74H150 tetraHeptakontanoatC9H20 Nonanoat C42H60 Dotetrakontanoat C75H152 pentaHeptakontanoatC10H22 Dekanoat C43H62 Tritetrakontanoat C76H154 heksaHeptakontanoatC11H24 Undekanoat C44H64 tetratetrakontanoat C77H156 heptaHeptakontanoatC12H26 Dodekanoat C45H66 Pentatetrakontanoat C78H158 oktaHeptakontanoatC13H28 Tridekanoat C46H68 heksatetrakontanoat C79H160 nonaHeptakontanoatC14H30 Tetradekanoat C47H70 heptatetrakontanoat C80H162 OktakontanoatC15H32 Pentadekanoat C48H72 oktatetrakontanoat C81H164 henOktakontanoatC16H34 Heksadekanoat C49H74 nonatetrakontanoat C82H166 doOktakontanoatC17H36 Heptadekanoat C50H102 Pentakontanoat C83H168 triOktakontanoatC18H38 Oktadekanoat C51H104 Henpentakontanoat C84H170 tetraOktakontanoatC19H40 Nonadekanoat C52H106 dopentakontanoat C85H172 pentaOktakontanoatC20H42 Eikosanoat C53H108 tripentakontanoat C86H174 heksaOktakontanoatC21H44 Heneikosanoat C54H110 tetrapentakontanoat C87H176 heptaOktakontanoatC22H46 Dokosanoat C55H112 pentapentakontanoat C88H178 oktaOktakontanoatC23H48 Trikosanoat C56H114 heksapentakontanoat C89H180 nonaOktakontanoatC24H50 Tetrakosanoat C57H116 heptapentakontanoat C90H182 NonakontanoatC25H52 Pentakosanoat C58H118 Oktapentakontanoat C91H184 henNonakontanoatC26H54 Heksakosanoat C59H120 nonapentakontanoat C92H186 doNonakontanoatC27H56 Heptakosanoat C60H122 Heksa kontanoat C93H188 triNonakontanoatC28H58 Oktakosanaoat C61H124 HenHeksa kontanoat C94H190 tetraNonakontanoatC29H60 Nonakosanoat C62H126 doHeksa kontanoat C95H192 pentaNonakontanoatC30H62 Triakontanoat C63H128 triHeksa kontanoat C96H194 heksaNonakontanoatC31H64 Hentriakontanoat C64H130 tetraHeksa kontanoat C97H196 HeptaNonakontanoatC32H66 Dotriakontanoat C65H132 pentaHeksa kontanoat C98H198 oktaNonakontanoatC33H68 Tritriakontanoat C66H134 heksaHeksa

kontanoatC99H200 nonaNonakontanoat

C100H202 Hektanoat C400H802 Tetrahektanoat C700H1402 HeptahektanoatC200H402 Dohektanoat C500H1002 Pentahektanoat C800H1602 OktahektanoatC300H6002 Trihektanoat C600H12002 Heksahektanoat C900H1802 NonahektanoatC1000H2002 Kilianoat C400H8002 Tetralianoat C700H14002 HeptalianoatC2000H4002 Dilianatanoat C500H10002 Penliaanoat C800H16002 OktalianoatC3000H6002 Trilianoat C600H1202 Heksalianoat C900H18002 Nonalianoat

Sintesa alkanoat

a. RCH2CH2OH + (O) RCH2COOH b. RCH2CH=O + Ag(NH3)2

+ R –CH2-COOH

83

c. R-CH-CO-CH3 + NaOX R –CH2-COOH

d. R-CH2 MgX + CO2 + H+ RCH2COOH

H3O+

e. RCH2CN + H2O RCH2COOH + NH3

f. RCH2CONH2 + H2O RCH2COOH

g. RCH2COOR + H2O RCH2COOH + ROH

h. RCH2COOX + H2O RCH2COOH + HX

i. (RCH2CO2)2 + H2O 2 RCH2COOH

Alkil amina

Amines and AmidesMain articles: Amine and Amide

Amines (R-NH2) are named for the attached alkane chain with the suffix "-amine" (e.g. CH3NH2 methanamine). If necessary, the bonding position is infixed: CH3CH2CH2NH2 propan-1-amine, CH3CHNH2CH3 propan-2-amine. The prefix form is "amino-".

For secondary amines (of the form R-NH-R), the longest carbon chain attached to the nitrogen atom becomes the primary name of the amine; the other chain is prefixed as an alkyl group with location prefix given as an italic N: CH3NHCH2CH3 is N-methylethanamine. Tertiary amines (R-NR-R) are treated similarly: CH3CH2N(CH3)CH2CH2CH3 is N-ethyl-N-methylpropanamine. Again, the substituent groups are ordered alphabetically.

84

Amides (R-CO-NH2) take the suffix "-amide". There is no prefix form, and no location number is required since they always terminate a carbon chain, e.g. CH3CONH2 (acetamide) is named ethanamide.

Secondary and tertiary amides are treated similarly to the case of amines: alkane chains bonded to the nitrogen atom are treated as substituents with the location prefix N: HCON(CH3)2 is N,N-dimethylmethanamide.

Senyawa amina adalah merupakan turunan hidrokarbon yang mempunyai gugus amina pada salah satu atau beberapa atom karbonnya dalam rantai molekul hidrokarbon. Amina digolongkan menjadi amina primer RNH2, amina sekunder R2NH, dan amina tersier R3N yang ditentukan oleh derajad substuitusi atom nitrogennya Pemberina nama IUPAC dari senyawa amino didasrkan pada nama homolog induk alkil alkananya kemudian ditambah dengan amina dibelakangnya

Amina alifatik

Senyawa Nama Senyawa Nama Senyawa NamaCH4 Metil amiana C34H44 Tetratriakontil amina C67H136 heptaHeksakontil aminaC2H6 Etetil amina C35H46 Pentatriakonil amina C68H138 oktaHeksakontilaminaC3H8 Propil amina C36H48 Heksatriakontil amina C69H140 nonaHeksakontil aminaC4H10 Butil amina C37H50 Heptatriakontil amina C70H142 Heptakontil aminaC5H12 Pentil amina C38H52 Oktatriakontil amina C71H144 henHeptakontil aminaC6H14 Heksil amina C39H54 Nonatriakontil amina C72H146 DoHeptakontil aminaC7H16 Heptil amina C40H56 Tetrakontil amina C73H148 triHeptakontanaC8H18 Oktil amina C41H58 Hentetrakontil amina C74H150 tetraHeptakontanaC9H20 Nonil amina C42H60 Dotetrakontil amina C75H152 pentaHeptakontanaC10H22 Dekil amina C43H62 Tritetrakontil amina C76H154 heksaHeptakontanaC11H24 Undekil amina C44H64 Tetratetrakontil

aminaC77H156 heptaHeptakontana

C12H26 Dodekil amina C45H66 Pentatetrakontil amina

C78H158 oktaHeptakontana

C13H28 Tridekil amina C46H68 Heksatetrakontil amina

C79H160 nonaHeptakontana

C14H30 Tetradekil amina C47H70 Heptatetrakontil amina

C80H162 Oktakontana

C15H32 Pentadekilamina C48H72 Oktatetrakontil amina C81H164 henOktakontanaC16H34 Heksadekil

aminaC49H74 Nonatetrakontil

aminaC82H166 doOktakontana

C17H36 Heptadekil amina C50H102 Pentakontil amina C83H168 triOktakontanaC18H38 Oktadekil amina C51H104 Henpentakontana C84H170 tetraOktakontanaC19H40 Nonadekil amina C52H106 dopentakontana C85H172 pentaOktakontanaC20H42 Eikosil amina C53H108 tripentakontana C86H174 heksaOktakontanaC21H44 Heneikosil amina C54H110 tetrapentakontana C87H176 heptaOktakontanaC22H46 Dokosil amina C55H112 pentapentakontana C88H178 oktaOktakontanaC23H48 Trikosil amina C56H114 heksapentakontana C89H180 nonaOktakontanaC24H50 Tetrakosana C57H116 heptapentakontana C90H182 NonakontanaC25H52 Pentakosana C58H118 Oktapentakontana C91H184 henNonakontanaC26H54 Heksakosana C59H120 nonapentakontana C92H186 doNonakontanaC27H56 Heptakosana C60H122 Heksa kontana C93H188 triNonakontanaC28H58 Oktakosana C61H124 HenHeksa kontana C94H190 tetraNonakontanaC29H60 Nonakosana C62H126 doHeksa kontana C95H192 pentaNonakontanaC30H62 Triakontana C63H128 triHeksa kontana C96H194 heksaNonakontanaC31H64 Hentriakontana C64H130 tetraHeksa kontana C97H196 HeptaNonakontanaC32H66 Dotriakontana C65H132 pentaHeksa kontana C98H198 oktaNonakontanaC33H68 Tritriakontana C66H134 heksaHeksa kontana C99H200 nonaNonakontanaC100H202 Hektana C400H802 Tetrahektana C700H1402 Heptahektana

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C200H402 Dohektana C500H1002 Pentahektana C800H1602 OktahektanaC300H6002 Trihektana C600H12002 Heksahektana C900H1802 NonahektanaC1000H2002 kiliana C400H8002 Tetraliana C700H14002 HeptalianaC2000H4002 Dilianatana C500H10002 Penliaana C800H16002 OktalianaC3000H6002 Triliana C600H1202 Heksaliana C900H18002 Nonaliana

Amina alisiklikSikloaminaSintesa amina

a. RX + NH3 RNH3 X- + NaOH R NH2 + NaX + H2Ob. RX + RNH2 RRNH2X + NaOH RRNH + NaX + H2O

c. RX + RRNH RRRNHX + NaOH RRRN + NaX

d. RX + RRRN RRRNX + NaOH RRRRN + NaOH + H2O

e. RX + NaN3 RN3 + LiAlH4 H2O RNH2

ether

f. RX + NaCN RCN + LiAlH4 H2O RNH2

ether

h. C6H5NO2 + Zn + HCl C6H5NH2

i. RCN + LiAlH4 RCH2NH2

j. RCONR2 + LiAlH4 RCH2NHR2

O NOH NH2

k.

+ H2NOH C2H5OH Na

Sikloheksanon sikloheksilhidroksiamin sikloheksilamin

H2/Nil. CH3COH + NH3 CH3CH2NH2

m. RCONH2 + Br2 + 4 KOH RNH2 + K2CO3 + 2 KBr + 2 H2O

Alkil sulfide

Senyawa Nama Senyawa Nama Senyawa NamaCH4 Metil sulfida C34H44 Tetratriakontil sulfida C67H136 heptaHeksa kontanaC2H6 Etil sulfida C35H46 Pentatriakontil sulfida C68H138 oktaHeksa kontanaC3H8 Propil sulfida C36H48 Heksatriakontil C69H140 nonaHeksa kontana

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sulfidaC4H10 Butil sulfida C37H50 heptatriakontana C70H142 HeptakontanaC5H12 Pentil sulfida C38H52 oktatriakontana C71H144 henHeptakontanaC6H14 Heksil sulfida C39H54 nonatriakontana C72H146 DoHeptakontanaC7H16 Heptil sulfida C40H56 Tetrakontana C73H148 triHeptakontanaC8H18 Oktil sulfida C41H58 hentetrakontana C74H150 tetraHeptakontanaC9H20 Nonil sulfida C42H60 Dotetrakontana C75H152 pentaHeptakontanaC10H22 Dekil sulfida C43H62 Tritetrakontana C76H154 heksaHeptakontanaC11H24 Undekana C44H64 tetratetrakontana C77H156 heptaHeptakontanaC12H26 Dodekana C45H66 pentatetrakontana C78H158 oktaHeptakontanaC13H28 Tridekana C46H68 heksatetrakontana C79H160 nonaHeptakontanaC14H30 Tetradekana C47H70 heptatetrakontana C80H162 OktakontanaC15H32 Pentadekana C48H72 oktatetrakontana C81H164 henOktakontanaC16H34 Heksadekana C49H74 nonatetrakontana C82H166 doOktakontanaC17H36 Heptadekana C50H102 Pentakontana C83H168 triOktakontanaC18H38 Oktadekana C51H104 Henpentakontana C84H170 tetraOktakontanaC19H40 Nonadekana C52H106 dopentakontana C85H172 pentaOktakontanaC20H42 Eikosana C53H108 tripentakontana C86H174 heksaOktakontanaC21H44 Heneikosana C54H110 tetrapentakontana C87H176 heptaOktakontanaC22H46 Dokosana C55H112 pentapentakontana C88H178 oktaOktakontanaC23H48 Trikosana C56H114 heksapentakontana C89H180 nonaOktakontanaC24H50 Tetrakosana C57H116 heptapentakontana C90H182 NonakontanaC25H52 Pentakosana C58H118 Oktapentakontana C91H184 henNonakontanaC26H54 Heksakosana C59H120 nonapentakontana C92H186 doNonakontanaC27H56 Heptakosana C60H122 Heksa kontana C93H188 triNonakontanaC28H58 Oktakosana C61H124 HenHeksa kontana C94H190 tetraNonakontanaC29H60 Nonakosana C62H126 doHeksa kontana C95H192 pentaNonakontanaC30H62 Triakontana C63H128 triHeksa kontana C96H194 heksaNonakontanaC31H64 Hentriakontana C64H130 tetraHeksa kontana C97H196 HeptaNonakontanaC32H66 Dotriakontana C65H132 pentaHeksa kontana C98H198 oktaNonakontanaC33H68 Tritriakontana C66H134 heksaHeksa kontana C99H200 nonaNonakontanaC100H202 Hektana C400H802 Tetrahektana C700H1402 HeptahektanaC200H402 Dohektana C500H1002 Pentahektana C800H1602 OktahektanaC300H6002 Trihektana C600H12002 Heksahektana C900H1802 NonahektanaC1000H2002 kiliana C400H8002 Tetraliana C700H14002 HeptalianaC2000H4002 Dilianatana C500H10002 Penliaana C800H16002 OktalianaC3000H6002 Triliana C600H1202 Heksaliana C900H18002 Nonaliana

H2Oa. RX + H2S RSH + HXb. C = C + H2O -CH – CHOH

c. R-CH = CH2 + B2H6 (RCH2– CH2)3-B+ H2O2 RCH2– CH2OH OH-

H2O d. R-CH = CH2 + Hg(OCOCH3)2 R-CH = CH2 + NaBH4 R-CH = CH3 25 oC OH HgOCOCH3 OH

Alkil fosfat adalah senyawa organic yang mengandung gugus posfat dengan rumus umum

sebagai berikut :

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R-PO3H2

Senyawa Nama Senyawa Nama Senyawa NamaCH4 Metil posfat C34H44 tetratriakontana C67H136 heptaHeksa kontanaC2H6 Etil posfat C35H46 pentatriakontana C68H138 oktaHeksa kontanaC3H8 Propil posfat C36H48 heksatriakontana C69H140 nonaHeksa kontanaC4H10 Butane C37H50 heptatriakontana C70H142 HeptakontanaC5H12 Pentane C38H52 oktatriakontana C71H144 henHeptakontanaC6H14 Heksana C39H54 nonatriakontana C72H146 DoHeptakontanaC7H16 Heptana C40H56 Tetrakontana C73H148 triHeptakontanaC8H18 Oktana C41H58 hentetrakontana C74H150 tetraHeptakontanaC9H20 Nonana C42H60 Dotetrakontana C75H152 pentaHeptakontanaC10H22 Dekana C43H62 Tritetrakontana C76H154 heksaHeptakontanaC11H24 Undekana C44H64 tetratetrakontana C77H156 heptaHeptakontanaC12H26 Dodekana C45H66 pentatetrakontana C78H158 oktaHeptakontanaC13H28 Tridekana C46H68 heksatetrakontana C79H160 nonaHeptakontanaC14H30 Tetradekana C47H70 heptatetrakontana C80H162 OktakontanaC15H32 Pentadekana C48H72 oktatetrakontana C81H164 henOktakontanaC16H34 Heksadekana C49H74 nonatetrakontana C82H166 doOktakontanaC17H36 Heptadekana C50H102 Pentakontana C83H168 triOktakontanaC18H38 Oktadekana C51H104 Henpentakontana C84H170 tetraOktakontanaC19H40 Nonadekana C52H106 dopentakontana C85H172 pentaOktakontanaC20H42 Eikosana C53H108 tripentakontana C86H174 heksaOktakontanaC21H44 Heneikosana C54H110 tetrapentakontana C87H176 heptaOktakontanaC22H46 Dokosana C55H112 pentapentakontana C88H178 oktaOktakontanaC23H48 Trikosana C56H114 heksapentakontana C89H180 nonaOktakontanaC24H50 Tetrakosana C57H116 heptapentakontana C90H182 NonakontanaC25H52 Pentakosana C58H118 Oktapentakontana C91H184 henNonakontanaC26H54 Heksakosana C59H120 nonapentakontana C92H186 doNonakontanaC27H56 Heptakosana C60H122 Heksa kontana C93H188 triNonakontanaC28H58 Oktakosana C61H124 HenHeksa kontana C94H190 tetraNonakontanaC29H60 Nonakosana C62H126 doHeksa kontana C95H192 pentaNonakontanaC30H62 Triakontana C63H128 triHeksa kontana C96H194 heksaNonakontanaC31H64 Hentriakontana C64H130 tetraHeksa kontana C97H196 HeptaNonakontanaC32H66 Dotriakontana C65H132 pentaHeksa kontana C98H198 oktaNonakontanaC33H68 Tritriakontana C66H134 heksaHeksa kontana C99H200 nonaNonakontanaC100H202 Hektana C400H802 Tetrahektana C700H1402 HeptahektanaC200H402 Dohektana C500H1002 Pentahektana C800H1602 OktahektanaC300H6002 Trihektana C600H12002 Heksahektana C900H1802 NonahektanaC1000H2002 kiliana C400H8002 Tetraliana C700H14002 HeptalianaC2000H4002 Dilianatana C500H10002 Penliaana C800H16002 OktalianaC3000H6002 Triliana C600H1202 Heksaliana C900H18002 Nonaliana

Biasanya senyawa alkyl posfat terdapat dalam molekul DNA dan RNA.

Organometallics is the branch of chemical science studying the chemistry of molecules that have direct carbon-metal bonds. (Dec 30, 2005)

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s ,d, p blocks

Main group organometallic chemistry

Alkali and akaline earths organometallic Li, Na, K organyls Be organyls Mg organyls

Aluminium group

Silicon group Si organyls Ga organyls

Pb, Sb, Sn, Hg

Transition-metal organometallic chemistry

The organometallic chemistry of the transition elements is quite different from the main-group ones due to the availability for bonding of the n d orbitals with consequent ability for the central atom to change geometry and expand the octet.

Crystal field theory

Single σ-bonding1. M-alkyl

β-elimination

π-acceptor bonding

alkene complexes

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CO complexes

1. σ *→dσ 2. dπ→π *

These interactions are synergicin increading the M-CO bond strength. In fact, the second interaction, as known as pi backbonding increases the available electron density on the CO.

The partial filling of the π* orbital leads to a weakened C-O triple bond, as showed from the stretching frequencies (in cm-1) of CO free and in M/CO complexes.

Free CO 2143V(CO)6 1976Ni(CO)4 2057Cr(CO)6 2000

Arene complexes

Carbenes and carbynes compounds

Fischer carbenes

By treatment of a CO complex with a strong nucleophile

Schrock carbenes

90

Catalysis by organometallic compounds

Metathesis

Richard Schrock(MIT, USA) and Robert Grubbs (CalTech, USA) received 2005 Nobel prize for their work on the subject. Metathesis is the exchange of the termination between two alkenes [1]

It occurs via the carbene species nowaday known as Schrock's carbenes

1. ̂   Grubbs, Olefin metathesis, Tetrahedron

Ziegler-Natta polymerisation

Ziegler-Natta catalyst Ziegler in the 40's worked on the oligomerisation of ethylene by aluminium alkyls via the reaction HAl-R + CH2=CH2 -> HAl-CH2CH2-R

Enantioselective hydrogenation

Wilkinson's

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Hydroformylation

Hydroformylation Hydroformylation is the process that transforms an alkene into an aldehyde by reaction with CO.

The catalyst is a hydridocarbonyl complex, HCO(CO)5

Fischer-Tropsch synthesis

Fischer-Tropsch synthesis is the heterogeneously-catalysed formation of hydrocarbons (alkanes and alkenes) from CO and hydrogen (synthesis gas). It can be seen as the inverse of synthesis gas preparation (although this is usually from methane and lighter hydrocarbons). It is the heart of the gas-to-liquids processes developed commercially by big petrochemical firms in the 90's.

Organometallics in living systems

The only example of a biological molecule containing direct carbon-metal bonds is cobalamin, as known as vitamin B12

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MODUL VI.

VI. TEORI TENTANG STEREO KIMIA

Reaksi inversi Walden

Pada tahun 1896 seorang ahli kimia Jerman yang bernama Paul Walden menemukan

peralihan bentuk isomer dari bentuk enasiomer asam malat (+) menjadi bentuk asam malat

(-), perubahan bentuk enansiomer ini terjadi melalui sederet siklus reaksi substitusi

sederhana. Bila bentuk isomer asam malat (-) direaksikan dengan PCl5 maka akan

terbentuk isomer asam klorosuksinat (+). Bila asam khloro suksinat (+) direaksikan

dengan Ag2O, maka akan terbentuk asam malat (+). Bila asam malat (+) direaksikan

dengan PCl5 dalam eter akan terbentuk isomer asam klorosuksinat (-). Selanjutnya bila

asam kloro suksinat (-) direaksikan dengan Ag2O dalam air akan terbentuk asam malat (-).

OH Cl

HO2C-CH2-CH-CO2HPCl5 HO2C-CH2-CH-CO2H

Asam malat (-) asam klorosuksinat (+)[ a]D = - 2,3

Ag2O H2O Ag2O H2O

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Cl OH

HO2C-CH2-CH-CO2HPCl5 HO2C-CH2-CH-CO2H

asam klorosuksinat (-) Asam malat (+) [ ]D = 2,3

Stereokimia dan reaksi substitusi nukleofilik

Sekalipun pada reaksi inverse Walden di atas terjadi perubahan konfigurasi yang berlangsung

dalam suatu siklus reaksi, namun tahap-tahap detil dari reaksi tersebut belum bisa diketahui.

Akan tetapi pada tahun 1920an Joseph Kenyon dan Henry Philips melalui sederet pengujian

yang dirancang untuk menentukan stereokimia dari reaksi substitusi, menemukan bahwa

adanya gugus asam karboksilat pada perlakuan Walden membuat masalah jadi rumit, oleh

karena itu dia melakukan reaksi yang lebih sederhana. Diantara sekian banyak pengujiannya

dia meneliti peralihan dua isomer 1fenil2propanol dengan reaksi sebagai berikut :

OH O-Tos

-CH-CH-CH3 -CH-CH-CH3

-

fenil-2propanol [a]D = 33o [a]D = 31,1o

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O

HO- O-C-CH3

H2O

O

O- C-CH3 CH3 O

-CH-CH-CH3 -CH-CH-O-C-CH3

[a]D = 7o [a]D = -7o

CH3 CH3

-CH2CH-O-Tos -CH2-CH-OH

[a]D = 31,0o [a]D = 33,2o

Kinetika Reaksi substitusi nukleofilikPara ahli kimia telah sepakat bahwa secara kualitatif suatu reaksi ditentukan oleh reaksi yang

lambat. Kecepatan pada saat bahan baku bereaksi memebntuk produk disebut kecepatan

reaksi, yang besarnanya dapat diukur. Penentuan kecepatan rreaksi dan ketergantungan

kecepatan reaksi terhadap konsentrasi reagen merupakan cara yang bisa digunakan untuk

menentukan mekanisme reaksi. Dari reaksi substitusi nukleofilik berikut :

H- + CH3Br ------------- HO-CH3 + Br-

Kecepatan reaksi = kecepatan hilangnya konsentrasi bahan baku

= k x [RX] x [HO-]

Dimana k = konstanta kecepatan reaksi

[RX] = konsentrasi CH3Br

[HO-] = konsentrasi HO-

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Reaksi SN1

Reaksi SN1 berati reaksi ini adalah reaksi substusi nukleofilik Orde satu.

Reaksi SN2

Reaksi SN2 erati reaksi ini adalah reaksi substusi nukleofilik Orde dua.

Kinetika reaksi substitusi elekrofilik

MEKANISME REAKSI SUBSTITUSI (SN) DAN ELIMINASI (E)

Reaksi Substitusi Nukleofilik

Reaksi substitusi nukleofilik (SN1 dan SN2) sangat erat kaitannya dengan E1 dan reaksi eliminasi E2, dibahas kemudian di bagian ini, dan umumnya ide yang baik untuk mempelajari reaksi bersama-sama, karena ada kesejajaran dalam mekanisme reaksi, substrat yang disukai, dan reaksi kadang-kadang bersaing satu sama lain

Sangat penting untuk memahami bahwa substitusi dan eliminasi reaksi tidak berhubungan dengan senyawa tertentu atau campuran begitu banyak karena mereka representasi dari bagaimana reaksi tertentu terjadi. Kadang-kadang, kombinasi dari mekanisme ini dapat terjadi bersama dalam reaksi yang sama atau mungkin bersaing satu sama lain, dengan pengaruh seperti pilihan pelarut atau nukleofil menjadi faktor penentu untuk yang reaksi akan mendominasi.

mencatatDalam notasi SN1 dan SN2,S adalah singkatan dari substitusi (sesuatu mengambil tempat sesuatu yang lain)N: singkatan nukleofilik (a menggantikan nukleofil nukleofil lain)1: singkatan unimolecular (konsentrasi hanya satu jenis molekul menentukan laju reaksi)2: singkatan Bimolekular (konsentrasi dua jenis molekul menentukan laju reaksi)

Dalam substitusi nukleofilik, nukleofil menyerang molekul dan mengambil tempat lain nukleofil, yang kemudian meninggalkan. Para nukleofil yang meninggalkan disebut kelompok pergi.Substitusi nukleofilik memerlukan1. nukleofil (seperti basa Lewis)2. sebuah elektrofil dengan sekelompok meninggalkanSekelompok meninggalkan adalah bagian bermuatan atau netral (kelompok) yang memecah gratis.

SN1 vs SN2Salah satu perbedaan utama antara SN1 dan SN2 adalah bahwa reaksi SN1 adalah reaksi 2-langkah, diprakarsai oleh disosiasi dari kelompok pergi. Reaksi SN2, di sisi lain, adalah reaksi 1-langkah di mana nukleofil menyerang, karena afinitas tinggi untuk dan ikatan kuat dengan karbon, memaksa kelompok meninggalkan pergi. Kedua hal ini terjadi dalam satu langkah.Kedua mekanisme yang berbeda menjelaskan perbedaan dalam laju reaksi antara SN1 dan SN2 reaksi. SN1 reaksi tergantung pada kelompok meninggalkan tidak dikaitkan dengan karbon. Ini

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adalah tingkat membatasi langkah dan dengan demikian, laju reaksi adalah reaksi orde pertama yang tingkat tergantung hanya pada langkah itu.

Rate = k[RX] Atau, dalam reaksi SN2, langkah tunggal nukleofil yang datang bersama-sama dengan reaktan dari sisi berlawanan dari kelompok pergi, adalah kunci untuk menilai nya. Karena itu, angka ini tergantung pada kedua konsentrasi nukleofil serta konsentrasi reaktan. Yang ini lebih tinggi dua konsentrasi, semakin sering tabrakan. Dengan demikian laju reaksi adalah reaksi orde kedua:Tingkat = k [Nu:] [RX] (di mana Nu: adalah nukleofil menyerang)

Reaksi SN2Ada terutama 3 hal yang mempengaruhi apakah reaksi SN2 akan berlangsung atau tidak. Yang paling penting adalah struktur. Itu adalah apakah alkil halida adalah pada metil, primer, karbon sekunder, atau tersier. Dua lainnya komponen yang menentukan apakah reaksi SN2 akan berlangsung atau tidak, adalah nucleophilicity dari nukleofil dan pelarut yang digunakan dalam reaksi.

Reactivity Due to Structure of SN2

CH3X > RCH2X > R2CHX >> R3CX

Struktur alkil halida memiliki efek yang besar pada mekanisme. CH3X & RCH2X adalah struktur yang lebih disukai untuk SN2. R2CHX dapat menjalani SN2 di bawah kondisi yang tepat (lihat bawah), dan R3CX jarang, jika pernah, terlibat dalam reaksi SN2.

Reaksi berlangsung oleh nukleofil menyerang dari sisi berlawanan dari atom brom. Perhatikan bahwa 3 lainnya Obligasi ini semua menunjuk jauh dari brom dan terhadap nukleofil menyerang. Saat ini 3 obligasi adalah obligasi hidrogen, ada hinderance sterik sangat sedikit dari nukleofil yang mendekat. Namun, karena meningkatnya jumlah R kelompok, demikian juga hinderance sterik, sehingga lebih sulit bagi nukleofil untuk mendapatkan cukup dekat dengan karbon α-, untuk mengusir atom brom. Bahkan, karbon tersier (R3CX) begitu sterik terhalang untuk mencegah mechanim SN2 dari mengambil tempat sama sekali.Dalam kasus contoh ini, sekunder α-karbon, masih banyak hinderance sterik dan dan apakah mekanisme SN2 akan terjadi akan tergantung sepenuhnya pada apa yang nukleofil dan pelarut. SN2 reaksi lebih disukai untuk metil halida dan halida primer.

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Hal penting lain yang perlu diingat, dan ini dapat dilihat dengan jelas dalam contoh di atas, selama reaksi SN2, molekul mengalami inversi sebuah. Obligasi melekat pada karbon-α yang menjauh sebagai pendekatan nukleofil. Selama keadaan transisi, obligasi ini menjadi planar dengan karbon dan, seperti daun brom dan obligasi nukleofil pada karbon-α, obligasi lainnya melipat kembali menjauh dari nukleofil tersebut. Hal ini sangat penting dalam molekul kiral atau pro-kiral, di mana konfigurasi R akan dikonversi menjadi konfigurasi S dan sebaliknya. Seperti yang akan Anda lihat di bawah, ini berbeda dengan hasil reaksi SN1.

contoh:OH-+ CH3-Cl → HO-CH3 + Cl-OH-adalah nukleofil tersebut, Cl adalah elektrofil, HOCH3 adalah produk, dan Cl-adalah kelompok pergi.atau,Na + I-+ CH3-Br → CH3 I-Na + + Br-Reaksi di atas, yang berlangsung di aseton sebagai natrium, pelarut dan iodida memisahkan hampir sepenuhnya dalam aseton, meninggalkan ion iodida bebas untuk menyerang CH-Br molekul. Ion iodida bermuatan negatif, nukleofil, menyerang molekul metil bromida, memaksa dari ion bromida bermuatan negatif dan mengambil tempat. Ion bromida adalah kelompok pergi.

NucleophilicityNucleophilicity adalah tingkat di mana nukleofil memindahkan kelompok berangkat reaksi. Umumnya, nucleophilicity adalah kuat, nukleofil yang lebih besar, lebih terpolarisasi, dan / atau kurang stabil. Tidak ada nomor tertentu atau satuan ukuran yang digunakan. Semua hal lain dianggap sama, nukleofil umumnya dibandingkan satu sama lain dalam hal reaktivitas relatif. Sebagai contoh, sebuah nukleofil kuat tertentu mungkin memiliki reaktivitas relatif dari 10.000 yang dari nukleofil lemah tertentu. Hubungan ini generalisasi sebagai hal-hal seperti pelarut dan substrat dapat mempengaruhi harga relatif, tapi mereka umumnya pedoman baik untuk spesies yang membuat nukleofil terbaik.Semua nukleofil adalah basa Lewis. Dalam reaksi SN2, yang nukleofil disukai adalah nukleofil kuat yang merupakan basa lemah. Contoh dari ini adalah N3-, RS-, I-, Br-, dan CN-.Atau, sebuah nukleofil kuat yang juga merupakan dasar yang kuat juga dapat bekerja. Namun, seperti yang disebutkan sebelumnya dalam teks, kadang-kadang mekanisme reaksi bersaing dan dalam kasus sebuah nukleofil kuat itu dasar yang kuat, mekanisme SN2 akan bersaing dengan mekanisme E2. Contoh nukleofil kuat yang juga basa kuat, termasuk RO-dan OH-.

List of descending nucleophilicities

I- > Br- > Cl- >> F- > -SeH > -OH > H2O

meninggalkan GrupMembiarkan kelompok adalah kelompok pada substrat yang meninggalkan. Dalam hal suatu alkil halida, ini adalah ion halida yang meninggalkan atom karbon ketika serangan nukleofil. Kecenderungan nukleofil untuk meninggalkan adalah

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Relative Reactivity of Leaving Groups

I- > Br- > Cl- >> F-

Fluoride ions are very poor leaving groups because they bond very strongly and are very rarely used in alkyl halide substitution reactions. Reactivity of a leaving group is related to its basicity with stronger bases being poorer leaving groups.

Solvent

The solvent can play an important role in SN2 reactions, particularly in SN2 involving secondary alkyl halide substrates, where it can be the determining factor in mechanism. Solvent can also have a great effect on reaction rate of SN2 reactions.

The SN2 mechanism is preferred when the solvent is an aprotic, polar solvent. That is, a solvent that is polar, but without a polar hydrogen. Polar, protic solvents would include water, alcohols, and generally, solvents with polar NH or OH bonds. Good aprotic, polar solvents are HMPA, CH3CN, DMSO, and DMF.

A polar solvent is preferred because it better allows the dissociation of the halide from the alkyl group. A protic solvent with a polar hydrogen, however, forms a 'cage' of hydrogen-bonded solvent around the nucleophile, hindering its approach to the substrate.

pelarutPelarut dapat memainkan peran penting dalam reaksi SN2, khususnya di SN2 melibatkan substrat sekunder alkil halida, dimana dapat menjadi faktor penentu dalam mekanisme. Pelarut juga dapat memiliki efek besar pada laju reaksi SN2 reaksi.Mekanisme SN2 lebih disukai bila pelarut adalah, aprotik pelarut polar. Artinya, suatu pelarut yang polar, tetapi tanpa hidrogen kutub. Polar, pelarut protik akan mencakup air, alkohol, dan umumnya, pelarut polar dengan NH atau obligasi OH. Baik aprotik, pelarut polar adalah HMPA, CH3CN, DMSO, dan DMF.Sebuah pelarut polar lebih disukai karena lebih baik memungkinkan pemisahan halida dari kelompok alkil. Sebuah pelarut protik dengan hidrogen kutub, bagaimanapun, membentuk sebuah 'kandang' hidrogen ikatan pelarut sekitar nukleofil itu, menghambat pendekatannya terhadap substrat.

Relative Reactivity of Solvents

HMPA > CH3CN > DMF > DMSO >> H2O

SN1 Reactions

The SN1 mechanism is very different from the SN2 mechanism. In some of its preferences, its exactly the opposite and, in some cases, the results of the reaction can be significantly different.

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Like the SN2 mechanism, structure plays an important role in the SN1 mechanism. The role of structure in the SN1 mechanism, however, is quite different and because of this, the reactivity of structures is more or less reversed.

Reactivity Due to Structure of SN1

CH3X < RCH2X << R2CHX < R3CX

The SN1 mechanism is preferred for tertiary alkyl halides and, depending on the solvent, may be preferred in secondary alkyl halides. The SN1 mechanism does not operate on primary alkyl halides or methyl halides. To understand why this is so, let's take a look at how the SN1 mechanism works.

SN1 nucleophilic substitution of a generic halide with a water molecule to produce an alcohol.

At the top of the diagram, the first step is the spontaneous dissociation of the halide from the alkyl halide. Unlike the SN2 mechanism, where the attacking nucleophile causes the halide to leave, the SN1 mechanism depends on the ability of the halide to leave on its own. This requires certain conditions. In particular, the stability of the carbocation is crucial to the ability of the halide to leave. Since we know tertiary carbocations are the most stable, they are the best candidates for the SN1 mechanism. And with appropriate conditions, secondary carbocations will also operate by the SN1 mechanism. Primary and methyl carbocations however, are not stable enough to allow this mechanism to happen.

Once the halide has dissociated, the water acts as a nucleophile to bond to the carbocation. In theSN2 reactions, there is an inversion caused by the nucleophile attacking from the opposite side

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while the halide is still bonded to the carbon. In the SN1 mechanism, since the halide has left, and the bonds off of the α-carbon have become planar, the water molecule is free to attack from either side. This results in, primarily, a racemic mixture. In the final step, one of the hydrogens of the bonded water molecule is attacked by another water molecule, leaving an alcohol.

Note: Racemic mixtures imply entirely equal amounts of mixture, however this is rarely the case in SN1. There is a slight tendency towards attack from the opposite side of the halide. This is the result some steric hinderence from the leaving halide which is sometimes close enough to the leaving side to block the nucleophile's approach from that side.

Solvent

Like the SN2 mechanism, the SN1 is affected by solvent as well. As with structure, however, the reasons differ. In the SN1 mechanism, a polar, protic solvent is used. The polarity of the solvent is associated with the dielectric constant of the solvent and solutions with high dielectric constants are better able to support separated ions in solution. In SN2 reactions, we were concerned about polar hydrogen atoms "caging" our nucleophile. This still happens with a polar protic solvent in SN1 reactions, so why don't we worry about it? You have to keep in mind the mechanism of the reaction. The first step, and more importantly, the rate-limiting step, of the SN1 reaction, is the ability to create a stable carbocation by getting the halide anion to leave. With a polar protic solvent, just as with a polar aprotic solvent,we're creating a stable cation, however it's the polar hydrogens that stabilize the halide anion and make it better able to leave. Improving the rate-limiting step is always the goal. The "caging" of the nucleophile is unrelated to the rate-limiting step and even in its "caged" state, the second step, the attack of the nucleophile, is so much faster than the first step, that the "caging" can simply be ignored.

Summary

SN1, SN2, E1, and E2, are all reaction mechanisms, not reactions themselves. They are mechanisms used by a number of different reactions. Usually in organic chemistry, the goal is to synthesize a product. In cases where you have possibly competing mechanisms, and this is particular the case where an SN1 and an E1 reaction are competing, the dominating mechanism is going to decide what your product is, so knowing the mechanisms and which conditions favor one over the other, will determine your product.

In other cases, knowing the mechanism allows you to set up an environment favorable to that mechanism. This can mean the difference between having your product in a few minutes, or sometime around the next ice age.

So when you're designing a synthesis for a product, you need to consider, I want to get product Y, so what are my options to get to Y? Once you know your options and you've decided on a reaction, then you need to consider the mechanism of the reaction and ask yourself, how do I create conditions that are going to make this happen correctly and happen quickly?

Reaksi eliminasiReaksi substitusi nukleofilik dan reaksi Penghapusan berbagi banyak karakteristik umum, di atas yang, E1 dan SN1 serta E2 dan SN2 reaksi kadang-kadang dapat bersaing dan, karena produk mereka berbeda, penting untuk memahami keduanya. Tanpa memahami kedua jenis mekanisme, akan sulit untuk mendapatkan produk yang anda inginkan dari reaksi.Selain itu, SN1 dan SN2 reaksi akan dirujuk cukup sedikit dengan cara perbandingan dan kontras, jadi mungkin lebih baik untuk membaca bagian yang pertama dan kemudian lanjutkan di sini.

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Reaksi eliminasi adalah mekanisme untuk menciptakan produk alkena dari reaktan haloalkana. E1 dan E2 eliminasi, tidak seperti SN1 dan SN2 substitusi, mekanisme tidak terjadi dengan metil halida karena reaksi menciptakan ikatan ganda antara dua atom karbon dan methylhalides hanya memiliki satu karbon.

mencatatDalam notasi E1 dan E2,E adalah singkatan dari eliminasi1: singkatan unimolecular (konsentrasi hanya satu jenis molekul menentukan laju reaksi)2: singkatan Bimolekular (konsentrasi dua jenis molekul menentukan laju reaksi)

E1 vs E2reaksi hargaE1 dan E2 adalah dua jalur yang berbeda untuk menciptakan alkena dari haloalkanes. Seperti SN1 dan SN2 reaksi, salah satu perbedaan utama adalah dalam laju reaksi, karena menyediakan wawasan besar ke dalam mekanisme.Reaksi E1, seperti SN1 reaksi adalah 2-langkah reaksi. Juga seperti reaksi SN1, tingkat membatasi langkah adalah disosiasi dari halida dari alkana nya, sehingga reaksi orde pertama, tergantung pada konsentrasi haloalkana, dengan laju reaksi dari:Tingkat = k [RX]Di sisi lain, reaksi E2, seperti reaksi SN2 1-langkah reaksi. Dan lagi, seperti dengan reaksi SN2, tingkat membatasi langkah adalah kemampuan nukleofil untuk melampirkan alkana dan menggantikan halida. Jadi itu adalah reaksi orde kedua yang tergantung pada konsentrasi dari kedua nukleofil dan haloalkana, dengan tingkat reaksi:Tingkat = k [Nu:] [RX] (di mana Nu: adalah nukleofil menyerang)

Zaitsev di PeraturanAturan Zaitsev itu (kadang-kadang dieja "Saytzeff") menyatakan bahwa dalam reaksi eliminasi, ketika beberapa produk yang mungkin, alkena paling stabil adalah produk utama. Artinya, yang paling sangat alkena tersubstitusi (dalam alkena dengan hidrogen sebagian besar non-substituen), adalah produk utama.Kedua E1 dan E2 reaksi menghasilkan campuran produk, bila mungkin, tetapi umumnya mengikuti aturan Zaitsev itu. Kita akan lihat di bawah mengapa reaksi E1 mengikuti aturan Zaitsev yang lebih andal dan cenderung menghasilkan produk yang lebih murni.

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Dehidrohalogenasi reaksi (S)-2-bromo-3-metilbutanaGambar di atas merupakan dua jalur yang mungkin untuk dehidrohalogenasi dari (S)-2-bromo-3-metilbutana. Kedua produk potensial adalah 2-methylbut-2-ena dan 3-methylbut-1-ene. Gambar di kanan disederhanakan gambar dari produk molekul ditunjukkan pada gambar di tengah.Seperti yang Anda lihat di sebelah kiri, bromin adalah pada karbon kedua dan dalam reaksi E1 atau E2, hidrogen bisa dihapus baik dari 1 atau karbon 3. Aturan Zaitsev mengatakan bahwa hidrogen akan dihapus terutama dari karbon ke-3. Pada kenyataannya, akan ada campuran, tetapi sebagian besar produk akan 2-methylbut-2-ena oleh mekanisme E1. Dengan reaksi E2, seperti yang akan kita lihat nanti, ini mungkin tidak selalu menjadi kasus.

E2

Reactivity Due to Structure of E2

RCH2X > R2CHX >> R3CX

Mekanisme E2 adalah terpadu dan higly stereospesifik, karena dapat terjadi hanya jika H dan X kelompok meninggalkan berada dalam posisi anti-coplanar. Artinya, dalam proyeksi Newman, H dan X harus 180 °, atau anti-konfigurasi. Perilaku ini berakar dari tumpang tindih terbaik dari orbital 2p dari karbon yang berdekatan ketika ikatan pi harus terbentuk. Jika H dan meninggalkan kelompok tidak dapat dibawa ke dalam posisi ini karena struktur molekul, mekanisme E2 tidak akan terjadi.

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Mechanism of E2 elimination. Note the anti-coplanarity of the X-C-C-H atomsKarena itu, hanya memiliki molekul diakses HX anti-coplanar konformasi dapat bereaksi melalui rute ini. Selanjutnya, mekanisme E2 akan beroperasi bertentangan dengan aturan Zaitsev kalau hidrogen anti-coplanar hanya dari hasil kelompok meninggalkan dalam alkena paling stabil. Sebuah contoh yang baik tentang bagaimana ini bisa terjadi adalah dengan melihat bagaimana sikloheksana dan turunannya sikloheksena mungkin beroperasi dalam kondisi E2

E2 with preferential elimination

Let's look at the example above. The reactant we're using is 1-chloro-2-isopropylcyclohexane. The drawing at the top left is one conformation and the drawing below is after a ring flip. In the center are Newman projections of both conformations and the drawings on the right, the products.

If we assume we're treating the 1-chloro-2-isopropylcyclohexane with a strong base, for example CH3CH2O- (ethanolate), the mechanism that dominates is E2. There are 3 hydrogens off of the carbons adjacent to our chlorinated carbon. The red and the green ones are two of them. The third would be hard to show but is attached to the same carbon as the red hydrogen, angled a little down from the plane and towards the viewer. The red hydrogen is the only hydrogen that's 180° from the chlorine atom, so it's the only one eligible for the E2 mechanism. Because of this, the product is going to be only 3-isopropylcylcohex-1-ene. Notice how this is contrary to Zaitsev's rule which says the most substituted alkene is preferred. By his rule, 1-isopropylcyclohexene should be our primary product, as that would leave the most substituted alkene. However it simply can't be produced because of the steric hindrance.

The images below shows the molecule after a ring flip. In this conformation, no product is possible. As you can see from the Newman projection, there are no hydrogens 180° from the chlorine atom.

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So it's important, when considering the E2 mechanism, to understand the geometry of the molecule. Sometimes the geometry can be used to your advantage to preferentially get a single product. Other times it will prevent you from getting the product you want, and you'll need to consider a different mechanism to get your product.

Note: Often the word periplanar is used instead of coplanar. Coplanar implies precisely 180 degree separation and "peri-", from Greek for "near", implies near 180 degrees. Periplanar may actually be more accurate. In the case of the 1-chloro-3-isopropylcyclohexane example, because of molecular forces, the chlorine atom is actually slightly less than 180 degrees from both the hydrogen and the isopropyl group, so in this case, periplanar might be a more correct term.

E1

E1 elimination of an alkyl halide by a base

The E1 mechanism begins with the dissociation of the leaving group from an alkyl, producing a carbocation on the alkyl group and a leaving anion. This is the same way the SN1 reaction begins, so the same thing that helps initiate that step in SN1 reactions, help initiate the step in E1 reactions. More specifically, secondary and tertiary carbocations are preferred because they're more stable than primary carbocations. The choice of solvent is the same as SN1 as well; a polar protic solvent is preferred because the polar aspect stabilizes the carbocation and the protic aspect stabilizes the anion.

What makes the difference between whether the reaction takes the SN1 or E1 pathway then, must depend on the second step; the action of the nucleophile. In SN1 reactions, a strong nucleophile that's a weak base is preferred. The nucleophile will then attack and bond to the carbocation. In E1 reactions, a strong nucleophile is still preferred. The difference is that a strong nucleophile that's also a strong base, causes the nucleophile to attack the hydrogen at the β-carbon instead of the α-carbocation. The nucleophile/base then extracts the hydrogen causing the bonding electrons to fall in and produce a pi bond with the carbocation.

VII. Senyawa optis aktif

Beberapa model enansiomer

MODUL VII

VIII. PUSAT CHIRAL

Campuran rasemat

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Senyawa stereo isomer

Proyeksi struktur molekul organic

Stereoisomers are properly named using the Cahn-Ingold-Prelog (CIP) priority rules to decide which parts of the molecule to consider first.

The rules have evolved to cover many situations, but the basic rules are:

1. Consider the first atom of each part of the molecule. An atom with higher atomic number has higher priority. (e.g. I > Cl > C > H)

2. If the first atom of two groups is the same, consider the second atom(s) in the same way as the first. (e.g. -C(CH3)3 > -CH(CH3)2 > -CH2CH3 > -CH3). If this does not assign priority, consider the next atoms until there is a difference.

Realize that when you do this it will mean that sometimes groups with higher total weights will have lower priority because of a lower weight of the atom that connects them.

[edit] R & S NotationR-dan S-notasi menggunakan aturan prioritas CIP untuk tugas dari konfigurasi mutlak sekitar stereocenter.Pertama, menetapkan prioritas untuk setiap atom yang mengelilingi stereocenter.Prioritas ini didasarkan pada nomor atom.Kedua, menunjukkan atom prioritas terendah menjauh dari Anda. Ikuti arah 3 prioritas yang tersisa dari terendah hingga tertinggi.Sebuah arah berlawanan adalah S (latin: jahat) konfigurasi. Sebuah searah jarum jam adalah R (latin: rektus) konfigurasi.

Direction of the travel 1-2-3 dictates configuration

[edit] E-Z notation

Notasi R-/S- hanya berlaku untuk konfigurasi absolut dari pusat memiliki ikatan tunggal saja. Dalam hal ikatan ganda, cis / trans nomenklatur sistem tradisional tidak cukup akurat dan E-/Z- saat ini sedang disukai.Dasarnya, adalah lagi aturan prioritas CIP.

See main discussion: E-Z notation

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Retrieved from "http://en.wikibooks.org/wiki/Organic_Chemistry/Chirality/R-S_notational_system"Subject: Organic Chemistry

MODUL VIII

IX. KARBOHIDRAT (saccharida )

Klassifikasi karbohidrat

Karbohidrat adalah suatu molekul senyawa organic dengan rumus umum Cn(H2O)n, jumlah

atom karbon sama dengan jumlah molekul air dimana nilai n adalah bilangan bulat lebih

besar dari tiga. Karbohidrat yang paling sederhana adalah 2,3 dihidroksi propanal (gliseral

dehid).

Secara garis besarnya kelompok karbohidrat adalah aldosa dan ketosa. Aldosa yaitu

karbohdrat yang mempunyai gugus alkanal, sedangkan ketosa adalah aldehid yang

mempunyai gugus alkanon.

konfigurasi karbohidrat

9.1. Konfigurasi karbohidrat ada 2 macam :

9.1.1. Aldosa

9.1.2. Ketosa

9.1. Monosaccharida

Struktur yang paling sederhana dari aldosa adalah gliseral dehid dengan 1 atom C optis

aktif (puat Chiral). Gliseral dehid mempunyai dua bentuk enasiomer yakni D-Gliseral

dehid dan L-gliseraldehid.

9.1.1. aldotriosa

O O C H C H H OH HO H

CH2OH CH2OH

D-Gliseraldehid L-Gliseraldehid

9.1.3. aldotetrosa

Aldotetroasa adalah bentuk dari aldosa dengan 4 atom karbon yang mempunyai 4 bentuk

isomes optis aktif sebagai berikut :

O O O O

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C H C H C H C H

H OH HO H OH H H OH

H OH HO H H OH HO H

CH2OH CH2OH CH2OH CH2OH D triosa L triosa D erithrosa L erithrosa

9.1.4. Struktur dari Aldopentosa adalah sebagai berikut :

Aldopentoasa adalah bentuk dari aldosa dengan 5 atom karbon yang mempunyai 8 bentuk

isomes optis aktif sebagai berikut :

O O O O C H C H C H C HOH H H OH H OH OH H

OH H H OH OH H H OH

OH H H OH H OH OH H CH2OH CH2OH CH2OH CH2OH

L ribose D Ribose D Xylose L Xylose

O O O O C H C H C H C HOH H H OH HO H H OH

OH H H OH H OH HO H

H OH HO H H OH HO H CH2OH CH2OH CH2OH CH2OH

D Lyxose L Lyxose D Arabinose L Arabinose

9.1.5. Struktur dari Aldoheksosa yang mempunyai 6 atom C dan 16 isomer optis aktif sebagai berikut :

O O O O C H C H C H C H

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H OH HO H HO H H OH

H OH HO H HO H H OH

H OH HO H HO H H OH

H OH HO H H OH HO H

CH2OH CH2OH CH2OH CH2OH

D Allosa L Allosa D Talosa L Talosa

O O O O C H C H C H C H

H OH HO H HO H H OH

H OH HO H HO H H OH

HO H H OH H OH HO H

H OH HO H H OH HO H

CH2OH CH2OH CH2OH CH2OHD Gulosa L Gulosa D Mannosa L Mannosa

O O O O C H C H C H C H

HO H H OH HO H H OH

H OH HO H H OH HO H

HO H H OH HO H H OH

HO H H OH H OH HO H

CH2OH CH2OH CH2OH CH2OH

L Glukosa D Glukosa D Idosa L Idosa

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O O O O C H C H C H C H

H OH HO H HO H H OH

HO H H OH H OH HO H

HO H H OH H OH HO H

H OH HO H H OH HO H

CH2OH CH2OH CH2OH CH2OHD Galaktosa L Galaktosa D Altrosa L Altrosa

9.2.1. Struktur dari Ketotetrosa yang mempunyai 4 atom C dengan 2 isomer sebagai berikut :

CH2OH CH2OH

O O

H OH HO H

CH2OH CH2OH

D erithrulose L erithrulose

9.2.2. Struktur dari Ketopentosa yang mempunyai 5 atom C dengan 4 isomer optis aktif

sebagai berikut :

CH2OH CH2OH CH2OH CH2OH

O O O O

H OH HO H H OH HO H

H OH HO H HO H H OH

CH2OH CH2OH CH2OH CH2OH

D ribulose L ribulose D xylulose L Xylulose

9.2.3. Struktur dari Ketoheksosa yang mempunyai 6 atom C dengan 8 isomer optis aktif sebagai berikut

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CH2OH CH2OH CH2OH CH2OH

O O O O

H OH HO H HO H H OH

H OH HO H HO H H OH

H OH HO H H OH HO H

CH2OH CH2OH CH2OH CH2OHD psychose L psychose L tagatose D tagatose

CH2OH CH2OH CH2OH CH2OH

O O O O

H OH HO H HO H H OH

HO H H OH H OH HO H

H OH HO H H OH HO H

CH2OH CH2OH CH2OH CH2OHD sorbose L sorbose D fructose L fructose

9.3. Bentuk lingkar senyawa saccharida

Bentuk lingkar pada senyawa saccharida terjadi bila atom C1 bergabung dengan gugus

hidroksil pada atom C4 atau C5 sehingga terjadi bentuk senyawa lingkar furannosida atau

pirannosida seperti berikut :

CH2OH OH OH CH2OH CH2OH H H H H OH H OH OH H

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9.5. Disaccharide From Wikipedia, the free encyclopediaJump to: navigation, search

A disaccharide or biose[1] is the carbohydrate formed when two monosaccharides undergo a condensation reaction which involves the elimination of a small molecule, such as water, from the functional groups only. Like monosaccharides, disaccharides form an aqueous solution when dissolved in water. Three common examples are sucrose, lactose,[2] and maltose.

'Disaccharide' is one of the four chemical groupings of carbohydrates (monosaccharide, disaccharide, oligosaccharide, and polysaccharide).

Classification

There are two different types of disaccharides: reducing disaccharides, in which one monosaccharide, the reducing sugar, still has a free hemiacetal unit; and non-reducing disaccharides, in which the components bond through an acetal linkage between their anomeric centers and neither monosaccharide has a free hemiacetal unit. Cellobiose and maltose are examples of reducing disaccharides. Sucrose and trehalose are examples of non-reducing disaccharides. [3] [4]

Formation

Disaccharides are formed when two monosaccharides are joined together and a molecule of water is removed, a process known as condensation. For example; milk sugar (lactose) is made from glucose and galactose whereas the sugar from sugar cane and sugar beets (sucrose) is made from glucose and fructose. Maltose, another notable disaccharide, is made up of two glucose molecules.[5] The two monosaccharides are bonded via a dehydration reaction (also called a condensation reaction or dehydration synthesis) that leads to the loss of a molecule of water and formation of a glycosidic bond.[citation needed]

Properties

The glycosidic bond can be formed between any hydroxyl group on the component monosaccharide. So, even if both component sugars are the same (e.g., glucose), different bond combinations (regiochemistry) and stereochemistry (alpha- or beta-) result in disaccharides that are diastereoisomers with different chemical and physical properties.

Depending on the monosaccharide constituents, disaccharides are sometimes crystalline, sometimes water-soluble, and sometimes sweet-tasting and sticky-feeling.

Common disaccharides

Disaccharide Unit 1 Unit 2 BondSucrose (table sugar, cane sugar, beet sugar, or saccharose) glucose fructose α(1→2)βLactulose galactose fructose β(1→4)Lactose (milk sugar) galactose glucose β(1→4)Maltose glucose glucose α(1→4)

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Trehalose glucose glucose α(1→1)αCellobiose glucose glucose β(1→4)

Maltose and cellobiose are hydrolysis products of the polysaccharides, starch and cellulose, respectively.

Less common disaccharides include:[6]

Disaccharide Units BondKojibiose two glucose monomers α(1→2) [7]

Nigerose two glucose monomers α(1→3)Isomaltose two glucose monomers α(1→6)β,β-Trehalose two glucose monomers β(1→1)βα,β-Trehalose two glucose monomers α(1→1)β[8]

Sophorose two glucose monomers β(1→2)Laminaribiose two glucose monomers β(1→3)Gentiobiose two glucose monomers β(1→6)

Turanosea glucose monomer and a fructose monomer

α(1→3)

Maltulosea glucose monomer and a fructose monomer

α(1→4)

Palatinosea glucose monomer and a fructose monomer

α(1→6)

Gentiobiulosea glucose monomer and a fructose monomer

β(1→6)

Mannobiose[disambiguation needed  ] two mannose monomerseither α(1→2), α(1→3), α(1→4), or α(1→6)

Melibiosea galactose monomer and a glucose monomer

α(1→6)

Melibiulosea galactose monomer and a fructose monomer

α(1→6)

Rutinosea rhamnose monomer and a glucose monomer

α(1→6)

Rutinulosea rhamnose monomer and a fructose monomer

β(1→6)

Xylobiose two xylopyranose monomers β(1→4)

9.6. oligo saccharida.9.6.1. amylosa9.6.2. amilopektin

9.7. poli saccharida.

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3D structure of cellulose, a beta-glucan polysaccharide.

Polysaccharides are long carbohydrate molecules of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure, these macromolecules can have distinct properties from their monosaccharide building blocks. They may be amorphous or even insoluble in water.[1][2]

When all the monosaccharides in a polysaccharide are the same type, the polysaccharide is called a homopolysaccharide or homoglycan, but when more than one type of monosaccharide is present they are called heteropolysaccharides or heteroglycans.[3][4]

Examples include storage polysaccharides such as starch and glycogen, and structural polysaccharides such as cellulose and chitin.

Polysaccharides have a general formula of Cx(H2O)y where x is usually a large number between 200 and 2500. Considering that the repeating units in the polymer backbone are often six-carbon monosaccharides, the general formula can also be represented as (C6H10O5)n where 40≤n≤3000.

Structure

Natural saccharides are generally built of simple carbohydrates called monosaccharides with general formula (CH2O)n where n is three or more. A typical monosaccharide has the structure H-(CHOH)x(C=O)-(CHOH)y-H, that is, an aldehyde or ketone with many hydroxyl groups added, usually one on each carbon atom that is not part of the aldehyde or ketone functional group. Examples of monosaccharides are glucose, fructose, and glyceraldehyde [5]

Amylose is a linear polymer of glucose mainly linked with α(1→4) bonds. It can be made of several thousands of glucose units. It is one of the two components of starch, the other being amylopectin.

Polysaccharides are composed of long chains of monosaccharide units bound together by glycosidic bonds. Polysaccharides contain more than ten monosaccharide units. Definitions of

114

how large a carbohydrate must be to fall into the categories polysaccharides or oligosaccharides vary according to personal opinion.

Polysaccharides is an important class of biological polymers. Their function in living organisms is usually either structure- or storage-related. Starch (a polymer of glucose) is used as a storage polysaccharide in plants, being found in the form of both amylose and the branched amylopectin. In animals, the structurally similar glucose polymer is the more densely branched glycogen, sometimes called 'animal starch'. Glycogen's properties allow it to be metabolized more quickly, which suits the active lives of moving animals.

Cellulose and chitin are examples of structural polysaccharides. Cellulose is used in the cell walls of plants and other organisms, and is claimed to be the most abundant organic molecule on earth.[6] It has many uses such as a significant role in the paper and textile industries, and is used as a feedstock for the production of rayon (via the viscose process), cellulose acetate, celluloid, and nitrocellulose. Chitin has a similar structure, but has nitrogen-containing side branches, increasing its strength. It is found in arthropod exoskeletons and in the cell walls of some fungi. It also has multiple uses, including surgical threads.

Polysaccharides also include callose or laminarin, chrysolaminarin, xylan, arabinoxylan, mannan, fucoidan and galactomannan.

Function

Nutrition

Polysaccharides are common sources of energy. Many organisms can easily break down starches into glucose, however, most organisms cannot metabolize cellulose or other polysaccharides like chitin and arabinoxylans. These carbohydrates types can be metabolized by some bacteria and protists. Ruminants and termites, for example, use microorganisms to process cellulose.

Even though these complex carbohydrates are not very digestible, they may comprise important dietary elements for humans. Called dietary fiber, these carbohydrates enhance digestion among other benefits. The main action of dietary fiber is to change the nature of the contents of the gastrointestinal tract, and to change how other nutrients and chemicals are absorbed.[7][8] Soluble fiber binds to bile acids in the small intestine, making them less likely to enter the body; this in turn lowers cholesterol levels in the blood.[9] Soluble fiber also attenuates the absorption of sugar, reduces sugar response after eating, normalizes blood lipid levels and, once fermented in the colon, produces short-chain fatty acids as byproducts with wide-ranging physiological activities (discussion below). Although insoluble fiber is associated with reduced diabetes risk, the mechanism by which this occurs is unknown.[10]

Not yet formally proposed as an essential macronutrient, dietary fiber is nevertheless regarded as important for the diet, with regulatory authorities in many developed countries recommending increases in fiber intake.[7][8][11][12]

Storage polysaccharides

Starches

Starches are glucose polymers in which glucopyranose units are bonded by alpha-linkages. It is made up of a mixture of amylose (15–20%) and amylopectin (80–85%). Amylose consists of a

115

linear chain of several hundred glucose molecules and Amylopectin is a branched molecule made of several thousand glucose units (every chain of 24–30 glucose units is one unit of Amylopectin). Starches are insoluble in water. They can be digested by hydrolysis, catalyzed by enzymes called amylases, which can break the alpha-linkages (glycosidic bonds). Humans and other animals have amylases, so they can digest starches. Potato, rice, wheat, and maize are major sources of starch in the human diet. The formations of starches are the ways that plants store glucose.

Glycogen

Schematic 2-D cross-sectional view of glycogen. A core protein of glycogenin is surrounded by branches of glucose units. The entire globular granule may contain approximately 30,000 glucose units.[13]

A view of the atomic structure of a single branched strand of glucose units in a glycogen molecule.

Glycogen serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue. Glycogen is made primarily by the liver and the muscles, but can also be made by glycogenesis within the brain and stomach.[14]

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Glycogen is the analogue of starch, a glucose polymer in plants, and is sometimes referred to as animal starch, having a similar structure to amylopectin but more extensively branched and compact than starch. Glycogen is a polymer of α(1→4) glycosidic bonds linked, with α(1→6)-linked branches. Glycogen is found in the form of granules in the cytosol/cytoplasm in many cell types, and plays an important role in the glucose cycle. Glycogen forms an energy reserve that can be quickly mobilized to meet a sudden need for glucose, but one that is less compact than the energy reserves of triglycerides (lipids).

In the liver hepatocytes, glycogen can compose up to eight percent of the fresh weight (100–120 g in an adult) soon after a meal.[15] Only the glycogen stored in the liver can be made accessible to other organs. In the muscles, glycogen is found in a low concentration (one to two percent of the muscle mass). However, the amount of glycogen stored in the body—especially within the muscles, liver, and red blood cells [16] [17] [18] —mostly depends on physical training, basal metabolic rate, and eating habits such as intermittent fasting. Small amounts of glycogen are found in the kidneys, and even smaller amounts in certain glial cells in the brain and white blood cells. The uterus also stores glycogen during pregnancy to nourish the embryo.[15]

Glycogen is composed of a branched chain of glucose residues. It is stored in liver and muscles.

It is an energy reserve for animals. It is the chief form of carbohydrate stored in animal body. It is insoluble in water. It turns red when mixed with iodine. It also yields glucose on hydrolysis.

Structural polysaccharides

Arabinoxylans

Arabinoxylans are found in both the primary and secondary cell walls of plants and are the copolymers of two pentose sugars: arabinose and xylose.

Cellulose

The structural component of plants are formed primarily from cellulose. Wood is largely cellulose and lignin, while paper and cotton are nearly pure cellulose. Cellulose is a polymer made with repeated glucose units bonded together by beta-linkages. Humans and many other animals lack an enzyme to break the beta-linkages, so they do not digest cellulose. Certain animals such as termites can digest cellulose, because bacteria possessing the enzyme are present in their gut. Cellulose is insoluble in water. It does not change color when mixed with iodine. On hydrolysis, it yields glucose. It is the most abundant carbohydrate in nature.

Chitin

Chitin is one of many naturally occurring polymers. It forms a structural component of many animals, such as exoskeletons. Over time it is bio-degradable in the natural environment. Its breakdown may be catalyzed by enzymes called chitinases, secreted by microorganisms such as bacteria and fungi, and produced by some plants. Some of these microorganisms have receptors to simple sugars from the decomposition of chitin. If chitin is detected, they then produce enzymes to digest it by cleaving the glycosidic bonds in order to convert it to simple sugars and ammonia.

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Chemically, chitin is closely related to chitosan (a more water-soluble derivative of chitin). It is also closely related to cellulose in that it is a long unbranched chain of glucose derivatives. Both materials contribute structure and strength, protecting the organism.

Pectins

Pectins are a family of complex polysaccharides that contain 1,4-linked α-D-galactosyluronic acid residues. They are present in most primary cell walls and in the non-woody parts of terrestrial plants.

Acidic polysaccharides

Acidic polysaccharides are polysaccharides that contain carboxyl groups, phosphate groups and/or sulfuric ester groups.

Bacterial polysaccharides

Bacterial polysaccharides represent a diverse range of macromolecules that include peptidoglycan, lipopolysaccharides, capsules and exopolysaccharides; compounds whose functions range from structural cell-wall components (e.g., peptidoglycan), and important virulence factors (e.g., Poly-N-acetylglucosamine in S. aureus), to permitting the bacterium to survive in harsh environments (e.g., Pseudomonas aeruginosa in the human lung).[19] Polysaccharide biosynthesis is a tightly regulated, energy-intensive process and understanding the subtle interplay between the regulation and energy conservation, polymer modification and synthesis, and the external ecological functions is a huge area of research. The potential benefits are enormous and should enable for example the development of novel antibacterial strategies (e.g., new antibiotics and vaccines) and the commercial exploitation to develop novel applications.[20][21]

Bacterial capsular polysaccharides

Pathogenic bacteria commonly produce a thick, mucous-like, layer of polysaccharide. This "capsule" cloaks antigenic proteins on the bacterial surface that would otherwise provoke an immune response and thereby lead to the destruction of the bacteria. Capsular polysaccharides are water soluble, commonly acidic, and have molecular weights on the order of 100-1000 kDa. They are linear and consist of regularly repeating subunits of one to six monosaccharides. There is enormous structural diversity; nearly two hundred different polysaccharides are produced by E. coli alone. Mixtures of capsular polysaccharides, either conjugated or native are used as vaccines.

Bacteria and many other microbes, including fungi and algae, often secrete polysaccharides as an evolutionary adaptation to help them adhere to surfaces and to prevent them from drying out. Humans have developed some of these polysaccharides into useful products, including xanthan gum, dextran, welan gum, gellan gum, diutan gum and pullulan.

Most of these polysaccharides exhibit interesting and very useful visco-elastic properties when dissolved in water at very low levels.[22] This gives many foods and various liquid consumer products, like lotions, cleaners and paints, for example, a viscous appearance when stationary, but fluidity when the slightest shear is applied, such as when wiped, poured or brushed. This property is referred to as pseudoplasticity, or shear thinning.

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Viscosity of Welan gum

Shear Rate (rpm) Viscosity (cP)

0.3 23330

0.5 16000

1 11000

2 5500

4 3250

5 2900

10 1700

20 900

50 520

100 310

Aqueous solutions of the polysaccharide alone have a curious behavior when stirred. After stopping, the swirl continues due to momentum, then stops, and then reverses direction briefly. This recoil demonstrates the elastic effect of the polysaccharide chains previously streched in solution, returning to their relaxed state.

Cell-surface polysaccharides play diverse roles in bacterial ecology and physiology. They serve as a barrier between the cell wall and the environment, mediate host-pathogen interactions, and form structural components of biofilms. These polysaccharides are synthesized from nucleotide-activated precursors (called nucleotide sugars) and, in most cases, all the enzymes necessary for biosynthesis, assembly and transport of the completed polymer are encoded by genes organized in dedicated clusters within the genome of the organism. Lipopolysaccharide is one of the most important cell-surface polysaccharides, as it plays a key structural role in outer membrane integrity, as well as being an important mediator of host-pathogen interactions.

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The enzymes that make the A-band (homopolymeric) and B-band (heteropolymeric) O-antigens have been identified and the metabolic pathways defined.[23] The exopolysaccharide alginate is a linear copolymer of β-1,4-linked D-mannuronic acid and L-guluronic acid residues, and is responsible for the mucoid phenotype of late-stage cystic fibrosis disease. The pel and psl loci are two recently discovered gene clusters that also encode exopolysaccharides found to be important for biofilm formation. Rhamnolipid is a biosurfactant whose production is tightly regulated at the transcriptional level, but the precise role that it plays in disease is not well understood at present. Protein glycosylation, particularly of pilin and flagellin, is a recent focus of research by several groups and it has been shown to be important for adhesion and invasion during bacterial infection.[24]

9.7.1. hemiselulosa

9.7.2. selulosa

9.8. konformasi heksosa ada dua yaitu :

a. konformasi kursi H

O CH2OH

H OH

OH H O H H n

b. Konformasi sampan H

O CH2OH O

OH OH H O H n

Beberapa reaksi karbohidrat dengan perekasi kimia adalah sebagai berikut :120

O C H H3COCH + H3CI/Ag2O --------------- ( HCOCH3)n-1 O ( H OH)n

CH2OH CH2OCH3

O C H Ac-OCH + Ac2O --------------- ( HCOAc)n-1 O ( H OH)n

CH2OH CH2OAc

O C H ROCH + ROH/H+ --------------- ( HCOH)n-1 O ( H OH)n

CH2OH CH2OH

O C H CH2OH + NaBH4 --------------- ( H OH)n (H OH)n

CH2OH CH2OH

O C H COOH + Br2/H2O --------------- ( H OH)n ( HCOH)n

CH2OH CH2OH

O C H COOH + HNO3 -------------- ( H OH)n ( HCOH)n

121

CH2OH COOH

O O C H C - H + HCN/H2O + Na(Hg) ------ ( H OH) ( H OH)n

(HCOH)n

CH2OH CH2OCH3

O O C H C-H + H2NOH/Ac2O/NaOCH3 --- ( ( H OH)n (HCOH)n-1

CH2OH CH2OH

MODUL X

X. ASAM AMINO DAN PROTEIN

10.1. Klassifikasi asam amino

10.1.1. Asam amino netral

Nama Ringkasan BM Struktur Titik isoelektrik

Alanin Ala (A) 89 H3C-CH-COOH 6.0 NH2

Asparagin Asn (N) 132 H3N- C-CH2-CH-COOH 5.4 O NH2

Cysteine Cys (C) 121 HS-CH2-CH-COOH 5.0 NH2

Glutamine Gln (Q) 146 H3C- C-CH2-CH2CH-COOH 5.7122

O NH2

Glycine Gly (G) 75 CH2-COOH 6.0 NH2

Isoleusin Ile (I) 131 H3C-CH2-CH(CH3)-CH-COOH 6.0 NH2

Leusin Leu (L) 131 (H3C)2CH-CH2-CH-COOH 6.0 NH2

Methionine Met(M) 149 H3C-S-CH2-CH2-CH-COOH 5.7 NH2

Phenylalanine Phe (F) 165 C6H5-H2C-CH-COOH 5.5 NH2

Proline Pro (P) 115 H2C-CH-COOH 6.3 NH

Serine Ser (S) 105 HO-H2C-CH-COOH 5.7 NH2

Threonine Thr (T) 119 H3C-CHOHCH-COOH 6.0 NH2

Trypthophan Trp (W) 204 CH2-CH-COOH 5.9 NH2

N

Tyrosine Tyr (Y) 181 p-OH-C6H4H2C-CH-COOH 5.7 NH2

Valine Val (V) 117 (H3C)2CH-CH-COOH 6.0 NH2

10.1.2. Asam amino asam

123

Aspartic Asp (D) 133 HOOC-CH2-CH-COOH 3.0 NH2

Glutamic Glu (E) 147 HOOC-CH2 -H2C-CH-COOH 3.2 NH2

10.1.3. Asam amino basa

Arginine Arg (R 174 H2N- C-NH-(H2C)3-CH-COOH 6.0 NH NH2

Histidine his (H) 155 H2C-CH-COOH 6.0 NH2

N N Lysine Lys (K) 146 H2N- (H2C)4-CH-COOH 6.0 NH2

10.2. sintesa asam amino

10.2.1. sintesa asam amino dengan pereaksi posfohalida

R-CHOH-COOH + PBr3 ---------------- RCHBr-COOH + NH3 ------ RCHNH2-COOH + HBr

10.2.2. sintesa asam amino dengan asam sianida dalam suasana asam

RCHO + HCN + H3O+ + NH4Cl---------------------- RCHNH2-COOH

10.2.3. sintesa asam amino dengan alkanonoat

RCOCOOH + NH3 + NaBH4 ------------------- RCHNH2COOH

10.4. sintesa asam amino dengan dietil asetamidomalonat

H3CCONHCH(CO2C2H5)2 + RX + H3O+ + NaOC2H5 ---------------- H2NRCHCOOH

10.3. Ikatan peptide

ikatan peptide adalah ikatan yang terjadi akibat reaksi dehidrolisa gugus -NH2 dan -COOH dari

beberapa asam amino membentuk molekul protein sebagai berikut :124

R-CHNH2-COOH + R’CHNHH-COOH ----------- R-CHNH2-CO-NH-COOH + H-O-H

CH

R’

Blocking Gugus -NH2 Pada asam amino dari reaksi sintesa protein

{(H3C)3COCO}2O

Ditert-butil dikarbonat

Blocking Gugus -COOH Pada asam amino dari reaksi sintesa protein

- H3COH

- PhCH2OH

10.4. Struktur protein

struktur protein tersusun dari ikatan peptida primer, sekunder, tertier, dan kuartener membentuk

rantai helik seperti jalinan talitemali

contoh protein angiotensin II yang terdapat dalam plasma darah

H2N-D-R-V-Y-I-H-P-F-COOH

Klassifikasi protein berdasarkan konformasinya

Protein sumber

Fibrous protein

Kolagen jaringan penghubung, urat

keratin rambut, kulit, kuku, tanduk

Elastin jaringan penghubung elastis

Potein globuler

Insulin hormone kontrol metabolisme glukosa

Lysozyme enzim hidrolitik

Ribonuklease enzim control sintesa RNA

Albumin protein menggumpal oleh panas

Immunoglobulin immune respon

Myoglobulin oksigen transport

Klassifikasi protein konyugasi ( protein yang mengandung senyawa selain asam amino seperti

karbohidrat, ester gliserida, asam nukleat, 125

Protein non asam amino nonasam amino (%)

Glycoprotein

-Globulin karbohidrat 10

Karboksipeptidase karbohidrat 17

Interferon karbohidrat 20

Lipoprotein

Plasma -lipoprotein lemak, kolesterol 80

Nucleoprotein

Ribosomal protein RNA 60

Virus tembakau RNA 5

Posfoprotein

Casein ester posfat 4

Metallo protein

Ferritin FeO 23

Hemoglobin Fe 0.3

Struktur insulin

21 asama amino rantai I

H2N-G-I-V-E-Q-C-C-T-S-I-C-S-L-Y-Q-L-E-N-Y-C-N-OH

30 asam amino rantai II

H2N-F-V-N-E-H-L-C-G-S-H-L-V-E-A-L-Y-L-V-C-G-E-R-G-F-F-Y-Y-P-L-Y-OH

MODUL X.

XI. ESTER TRIGLISERIDA(lipid)

Ester gliserida adalah senyawa molekul organic yang didapatkan dialam dipisahkan dari

sel dan jaringan biota dengan cara ekstraksi dengan pelarut organic non polar. Lipid biasanya

terdiri dari atom karbon yang banyak dalam strukturnya yang larut dalam pelarut organic non

polar dan tak larut dalam air. Lipid lebih ditentukan oleh sifat fisikanya dari pada sifat

kelarutannya sebagaimana halnya dengan karbohidrat dan protein. Ester gliserida tersusun dari

gliserol atau alkanol berberat molekul besar dengan asam lemak.

Ester gliserida dapat digolongkan menjadi 2 golongan besar yakni lipid kompleks seperti

lemak dan lilin yang mengandung ikatan ester dan dapat dihidrolisa menjadi molekul kecil,

dan lipid sederhana yang tidak dapat dihidrolisa seperti kolesterol dan steroid lainnya. Struktur

ester gliserida adalah sebagai berikut :

126

CH2-O-CO-R

CH-O-CO-R

CH2-O-CO-R

Berdasarkan konfigurasi ikatan asam lemak pada gliserol ada 4 konfigurasi yaitu :

CH2-O-CO-R

CH-O-CO-R

CH2-O-CO-R

Lurus

CH2-O-CO-R

RO-CO-C-H

CH2-O-CO-R

Garpu

R-OC-O-CH2

CH-O-CO-R

CH2-O-CO-R

Kursi

CH2-O-CO-R

CH-O-CO-R

R-OC-O-CH2

topi

Jika lipid dihidrolisa akan terurai menjadi gliserol dan asam-asam lemak

CH2-O-CO-R CH2OH RCOOH

CH-O-CO-R’ + 3H3O+ ------------------ CH-OH + R’COOH

CH2-O-CO-R” CH2OH R”COOH

Ester gliserida gliserol asam lemak

11. 1. Klassifikasi ester gliserida

a. minyak adalah asam lemak tak jenuh dan jenuh berikatan dengan gliserol membentuk ester127

CH2-O-CO-R

CH-O-CO-R

CH2-O-CO-(HC=CH)nR

b. lemak adalah asam lemak jenuh dengan gliserol membentuk ester

CH2-O-CO-R

CH-O-CO-R

CH2-O-CO-R

c. posfolipid adalah asam lemak dan senyawa basa posfolipid membentuk ester

- L Lecitin (kuning telor)

CH2-O-CO-R

R-COO-C-H

CH2-O-PO3-CH2-CH2-N+(CH3)3

- cephlin (otak)

CH2-O-CO-R

R-COO-C-H

CH2-O-PO3-CH2-CH2-N+H3

- sphingosin

CH2-OH

CH-NH2

CH-OH

CH=CH(CH2)12CH3

- sphingomyelin

CH2-OPO3-CH2-CH2-N+(CH3)3

CH-NH-CO-(CH2)16-24-CH3

CH-OH

CH=CH(CH2)12CH3

d. malam adalah asam lemak berberat molekul besar dengan alkanol berberat molekul besar128

CH3(CH2)20-24-COO-(CH2)27CH3

Lilin lebah

Jenis-jenis asam lemak

Nama struktur BP (oC)

Asam lamak jenuh

Laurat H3C-(CH2)10-COOH 44

Mirisitat H3C-(CH2)12-COOH 58

Palmitat H3C-(CH2)14-COOH 63

Stearat H3C-(CH2)16-COOH 70

Arachidat H3C-(CH2)10-COOH 75

Asam lemak tak jenuh

Palmitoleat H3C-(CH2)5HC=CH-(CH2)7-COOH 32

Oleat H3C-(CH2)7HC=CH-(CH2)7-COOH 4

Ricinileat H3C-(CH2)5CHOH-CH2-HC=CH-(CH2)7-COOH (cis) 5

Linoleat H3C-(CH2)3-(CH2-HC=CH)2-(CH2)7-COOH (cis,cis) -5

Linolenat H3C-(CH2-HC=CH-)3-(CH2)7-COOH (cis,cis,cis) -11

Arachidonat H3C-(CH2)4-(CH2-HC=CH)4-(CH2)2-COOH (cis4x) -50

Komposis (%) asam lemak pada berbagai sumber bahan alami

Asam lemak jenuh asam lamak tak jenuh

Sumber L M P S O R Li Lin

Hewan

Lemak babi - 1 25 15 50 - 6 1

Butter 2 10 25 10 25 - 5 -

Lemak manusia 1 3 25 8 46 - 10 -

Lemak ikan paus - 8 12 3 35 - 10 -

Tumbuhan

Kelapa 50 18 8 2 6 - 1 -

Jagung - 1 10 4 35 - 45 -

Zaitun - 1 5 5 80 - 7 -

Kacang tanah - - 7 5 60 - 20 -

Biji bunga matahari - - 5 3 20 - 20 50

Biji jarak - - - 1 8 85 4 -129

Reaksi sintesa ester gliserida

a. RCOOH + OHCH2-CHOH-CH2OH ROOCH2-CHCOOR-CH2COOR

H3CO-S-synthetase + HOOC-CH2CO-S-ACP H3C-CO

H-C-CO-S-ACP

COOH

H3C-CO-CH2-CO-S-ACP + CO2Asetoasetil ACP (acyl carrier protein)

Biosintesa lipid

H3C-CO-SCoA

Asetil CoA

ACP transferase Asetil CoAcarboksilase

HS-ACP CO2

H3C-CO-SACP HOOC-CH2-CO-SCoA

Malonil CoA

KetoACP transferase ACP transferase, HSACP

H3C-CO-SSynthetase HOOC-CH2-CO-SACP

Keto ACP synthetase

H3C-CO-CH2-CO-SACP + CO2 + HSCoA

NADPH, H+

130

H3C-HOH-CH2-CO-SACP

Enoyl ACP dehidrase

H3C-CH=CH-CO-SACP

NADPH

H3C-CH2-CH2-CO-SACP berulang

MODUL XI

ALKALOID

Struktur kimia dari efedrin, sebuah alkaloid phenethylamine

Alkaloid adalah senyawa alami kimia yang mengandung atom nitrogen dasar [1] Nama ini berasal dari kata basa dan digunakan untuk menggambarkan setiap basa nitrogen yang mengandung dan senyawa organik dengan satu atau lebih dari fitur berikut:. Senyawa heterosiklik yang mengandung nitrogen, dengan pH alkali dan tindakan fisiologis yang ditandai pada fisiologi hewan [kutipan diperlukan]. Namun, ada pengecualian untuk masing-masing kriteria. Alkaloid dihasilkan oleh berbagai macam organisme, termasuk bakteri, jamur, tumbuhan, dan hewan dan merupakan bagian dari kelompok produk alami (juga disebut metabolit sekunder). Banyak alkaloid dapat dimurnikan dari ekstrak mentah oleh ekstraksi asam-basa. Banyak alkaloid yang beracun bagi organisme lain.

Mereka sering memiliki efek farmakologis dan digunakan sebagai obat, seperti narkoba, atau dalam ritual entheogenic. Contohnya adalah anestesi lokal dan kokain stimulan, kafein stimulan, nikotin, morfin analgesik, atau kina obat antimalaria. Alkaloid yang paling memiliki rasa pahit.

131

Caffeine, a Purine alkaloid

Struktur kimia Vinblastine, sebuah alkaloid Chemotheraputic terisolasi dari Madagaskar periwinkle

Alkaloid classificationsKlasifikasi dari alkaloid adalah kompleks dan dapat dipandu oleh seperangkat aturan yang mempertimbangkan struktur dan fitur kimia lainnya dari molekul alkaloid, asal biologisnya, serta asal biogenetis mana dikenal [2] [3]. Sebagai contoh, di mana jalur biosintesis alkaloid yang tidak diketahui, dapat dikelompokkan berdasarkan kemiripan struktur dengan senyawa yang diketahui, termasuk non-nitrogen senyawa, atau dengan organisme (s) dari yang alkaloid yang diisolasi. [3]

Pyridine group: piperine, coniine, trigonelline, arecoline, arecaidine, guvacine, cytisine, lobeline, nicotine, anabasine, sparteine, pelletierine.

Pyrrolidine group: hygrine, cuscohygrine, nicotine Tropane group: atropine, cocaine, ecgonine, scopolamine, catuabine Indolizine group: senecionine, swainsonine Quinoline group: quinine, quinidine, dihydroquinine, dihydroquinidine, strychnine,

brucine, veratrine, cevadine Isoquinoline group: opium alkaloids (papaverine, narcotine, narceine), pancratistatin,

sanguinarine, hydrastine, berberine, emetine, berbamine, oxyacanthine Phenanthrene alkaloids: opium alkaloids (morphine, codeine, thebaine, oripavine) Phenethylamine group: mescaline, ephedrine, dopamine Indole group:

o Tryptamines : serotonin, DMT, 5-MeO-DMT, bufotenine, psilocybino Ergolines (the ergot alkaloids): ergine, ergotamine, lysergic acido Beta-carbolines : harmine, harmaline, tetrahydroharmineo Yohimbans: reserpine, yohimbine

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o Vinca alkaloids : vinblastine, vincristineo Kratom (Mitragyna speciosa) alkaloids: mitragynine, 7-hydroxymitragynineo Tabernanthe iboga alkaloids: ibogaine, voacangine, coronaridineo Strychnos nux-vomica alkaloids: strychnine, brucine

Purine group: o Xanthines : caffeine, theobromine, theophylline

Terpenoid group: o Aconitum alkaloids: aconitineo Steroid alkaloids (containing a steroid skeleton in a nitrogen containing structure):

Solanum (e.g. potato and tomato) alkaloids (solanidine, solanine, chaconine)

Veratrum alkaloids (veratramine, cyclopamine, cycloposine, jervine, muldamine)[4]

Fire Salamander alkaloids (samandarin) Others: conessine

Quaternary ammonium compounds : muscarine, choline, neurine Miscellaneous: capsaicin, cynarin, phytolaccine, phytolaccotoxin

MODUL XII

XII. TERPENOID

Terpenoid adalah senyawa organic yang terdiri dari rantai isoprene mulai dari 10

dengan kelipatan 5 atom karbon

Klassifikasi terpenoid

a. monoterpen adalah gabaungan 2 molekul isoprena

konfigurasi isoprena pada monoterpen ada 4 kombinasi :

Isoprena

- Belakang belakang

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- Belakang depan

- Depan belakang

- Depan depan

b. sesquiterpen 3 molekul isoprene jumlah atom C = 15

c. diterpen 4 molekul isoprene jumlah atom C = 20

d. sesterterpen 5 molekul isoprene jumlah atom C = 25

e. triterpen 6 molekul isoprene jumlah atom C = 30

f. tetraterpen 8 molekul isoprene jumlah atom C = 40

Reaksi sintesa terpenoid

OPP + OPP OPP

IPP DAPP

CH2OH CH2OPP

Geraniol GPP

CH2OPP134

CH2OPP

+

GeraniolPP nerolPP limonen

CH2OPP CH2OPP

+

GPP

CH2OPP + -:OPP

CH2OPP

Farnesol piroposfat

CH2OH135

Farnesol

CH2OPP

Farnesol piroposfat

+

o CH2OPP

Farnesol piroposfat

squalena

MODUL XIII

XIII. STEROID

Steroid

From Wikipedia, the free encyclopedia

Jump to: navigation, searchThis article is about the chemical family of lipids. For the performance-enhancing substance, see Anabolic steroid.

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IUPAC recommended ring lettering (left) and atom numbering (right) of the steroid skeleton.[1][2]

The four rings A-D form a sterane core.

Stick model of the steroid lanosterol. The total number of carbons (30) reflects its triterpenoid origin.

.

Sebuah steroid merupakan lipid terpenoid dicirikan oleh inti sterane dan kelompok fungsional tambahan. Inti adalah struktur karbon dari empat cincin leburan: tiga cincin sikloheksana dan satu cincin cyclopentane. Steroid bervariasi oleh kelompok-kelompok fungsional yang melekat pada cincin ini dan keadaan oksidasi dari cincin.Ratusan steroid yang berbeda ditemukan pada tumbuhan, hewan, dan jamur. Semua steroid yang dibuat dalam sel baik dari lanosterol sterol (hewan dan jamur) atau cycloartenol (tanaman). Kedua, lanosterol dan cycloartenol, berasal dari siklisasi dari squalene triterpene. [3]Sterol adalah bentuk khusus dari steroid, dengan kelompok hidroksil pada atom C-3 dan kerangka berasal dari kolestan [2] Kolesterol adalah salah satu sterol yang paling dikenal..

Klasifikasi

Taksonomi / FungsionalBeberapa kategori umum dari steroid:• Hewan steroido steroid Serangga Ecdysteroids seperti ecdysterone

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o Vertebrata steroid steroid hormon steroid Seks adalah subset dari hormon seks yang menghasilkan perbedaan seks atau reproduksi dukungan. Mereka termasuk androgen, estrogen, dan progestagens. Kortikosteroid meliputi glukokortikoid dan mineralokortikoid. Glukokortikoid mengatur banyak aspek metabolisme dan fungsi kekebalan tubuh, sedangkan mineralokortikoid membantu mempertahankan volume darah dan mengontrol ekskresi ginjal elektrolit. Kebanyakan medis 'steroid' obat kortikosteroid. Anabolic steroids adalah kelas steroid yang berinteraksi dengan reseptor androgen untuk meningkatkan otot dan sintesis tulang. Ada steroid anabolik alami dan sintetis. Dalam bahasa populer, kata "steroid" biasanya mengacu pada steroid anabolik. Kolesterol, yang memodulasi fluiditas membran sel dan merupakan konstituen utama dari plak terlibat dalam aterosklerosis.• Tanaman steroido Phytosterolso Brassinosteroids• Jamur steroido ergosterol

Structural

strukturalHal ini juga memungkinkan untuk mengklasifikasikan steroid berdasarkan komposisi kimianya. Salah satu contoh betapa MESH melakukan klasifikasi ini tersedia di katalog MESH Wikipedia. Contoh dari klasifikasi ini meliputi:

Class Examples Number of carbon atoms

Cholstanes cholesterol 27

Cholanes cholic acid 24

Pregnanes progesterone 21

Androstanes testosterone 19

Estranes estradiol 18

Gonane (or steroid nucleus) is the hypothetic parent (17-carbon tetracyclic) hydrocarbon molecule without any alkyl sidechains.[4]

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MetabolismSteroid meliputi estrogen, kortisol, progesteron, dan testosteron. Estrogen dan progesteron yang dibuat terutama di ovarium dan plasenta selama kehamilan, dan testosteron di testis. Testosteron juga diubah menjadi estrogen untuk mengatur pasokan masing-masing, dalam tubuh baik wanita dan pria. Neuron tertentu dan glia pada sistem saraf pusat (SSP) mengekspresikan enzim yang diperlukan untuk sintesis lokal neurosteroids pregnane, baik de novo atau dari sumber perifer yang diturunkan. Tingkat membatasi langkah sintesis steroid adalah konversi kolesterol menjadi pregnenolon, yang terjadi di dalam mitokondriaNew! Click the words above to edit and view alternate tra

Sederhana versi dari bagian akhir jalur sintesis steroid, dimana isopentenil intermediet pirofosfat (IPP) dan pirofosfat dimethylallyl (DMAPP) bentuk geranyl pirofosfat (GPP), squalene dan, akhirnya, lanosterol, steroid pertama dalam jalur. Beberapa intermediet dihilangkan untuk kejelasan.Metabolisme steroid adalah set lengkap reaksi kimia dalam organisme yang memproduksi, memodifikasi dan mengkonsumsi steroid. Jalur metabolik meliputi:• steroid sintesis - pembuatan steroid dari prekursor sederhana• steroidogenesis - yang interkonversi dari berbagai jenis steroid• steroid degradasi.

Steroid biosynthesis

Biosintesis steroid merupakan jalur metabolisme yang menghasilkan steroid anabolik dari prekursor sederhana. Jalur ini dilakukan dengan cara yang berbeda pada hewan daripada di banyak organisme lain, membuat jalur target umum untuk antibiotik dan obat anti infeksi. Selain

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itu, metabolisme steroid pada manusia merupakan target dari obat penurun kolesterol seperti statin.Dimulai di jalur mevalonate pada manusia, dengan Asetil-KoA sebagai blok bangunan yang membentuk DMAPP dan IPP [6]. Dalam langkah-langkah berikut, DMAPP dan IPP bentuk lanosterol, steroid pertama. Modifikasi lebih lanjut milik steroidogenesis berhasil

Mevalonate pathway

Mevalonate pathwayMain article: Mevalonate pathway

The mevalonate pathway or HMG-CoA reductase pathway starts with and ends with dimethylallyl pyrophosphate (DMAPP) and isopentenyl pyrophosphate (IPP).

Peraturan dan umpan balikBeberapa enzim kunci dapat diaktifkan melalui regulasi transkripsi DNA pada aktivasi SREBP (Sterol Peraturan Elemen-Binding Protein-1 dan -2). Sensor intraseluler mendeteksi kadar kolesterol rendah dan merangsang produksi endogen oleh jalur HMG-CoA, serta meningkatkan penyerapan lipoprotein dengan up-mengatur reseptor LDL. Peraturan jalur ini juga dicapai dengan mengendalikan laju terjemahan dari mRNA, degradasi reduktase dan fosforilasi

FarmakologiSejumlah obat menargetkan jalur mevalonate:• Statin (digunakan untuk kadar kolesterol tinggi)• Bifosfonat (digunakan dalam pengobatan berbagai penyakit degeneratif tulang)Tanaman dan bakteriPada tumbuhan dan bakteri, jalur non-mevalonate menggunakan piruvat dan gliseraldehida 3-fosfat sebagai substrat. [7] [8]DMAPP untuk lanosterolPirofosfat dan isopentenil pirofosfat dimethylallyl menyumbangkan unit isoprena, yang dirakit dan dimodifikasi untuk terpene bentuk dan isoprenoidnya [8], yang adalah kelas besar lipid yang mencakup karotenoid, dan membentuk kelas terbesar produk tanaman alami. [9]Di sini, unit isoprena bergabung bersama untuk membuat squalene dan kemudian dilipat dan dibentuk menjadi satu set cincin untuk membuat lanosterol [10]. Lanosterol kemudian dapat diubah menjadi steroid lain seperti kolesterol dan ergosterol. [10] [11]

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Human SteroidogenesissteroidogenesisSteroidogenesis adalah proses dimana bentuk yang diinginkan dari steroid yang dihasilkan oleh transformasi steroid lainnya (Pembentukan steroid; umumnya mengacu pada sintesis biologis hormon steroid, tetapi tidak untuk produksi senyawa tersebut di laboratorium kimia). Jalur dari steroidogenesis dapat berbeda dari organisme ke organisme, namun jalur dari steroidogenesis manusia diperlihatkan pada gambar.Produk dari steroidogenesis meliputi:

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• androgeno testosteron• estrogen dan progesteron• corticoidso kortisolo aldosteron

Elimination

Steroid terutama dioksidasi oleh sitokrom P450 oksidase enzim, seperti CYP3A4. Reaksi-reaksi memperkenalkan oksigen ke dalam cincin steroid dan memungkinkan struktur untuk dipecah oleh enzim lainnya, untuk membentuk asam empedu sebagai produk akhir. [12] Asam empedu kemudian dapat dieliminasi melalui sekresi dari hati dalam empedu. [13] ekspresi gen ini oksidase dapat diregulasi oleh PXR sensor steroid ketika ada konsentrasi darah tinggi steroid [14]

MODUL XIV

XIV. |FLAVONOID

Jump to: navigation, search

Molecular structure of the flavone backbone (2-phenyl-1,4-benzopyrone)

Isoflavan structure

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Neoflavonoids structureFlavonoid (atau bioflavonoid), juga yang dikenal sebagai vitamin P dan Citrin [1], adalah kelas metabolit sekunder tanaman. Menurut tata nama IUPAC, [2] mereka dapat diklasifikasikan menjadi:• flavonoid, berasal dari 2-phenylchromen-4-satu (2-fenil-1 ,4-benzopyrone) struktur (contoh: quercetin, rutin).• isoflavonoid, berasal dari 3-phenylchromen-4-satu (3-fenil-1 ,4-benzopyrone) struktur• neoflavonoids, berasal dari 4-phenylcoumarine (4-fenil-1 ,2-benzopyrone) struktur.Tiga kelas flavonoid di atas adalah semua keton yang mengandung senyawa, dan dengan demikian, flavonoid dan flavonol. Kelas ini adalah yang pertama yang akan disebut "bioflavonoid." Para flavonoid Ketentuan dan bioflavonoid juga telah lebih longgar digunakan untuk menggambarkan senyawa polihidroksi non-keton polifenol yang lebih khusus disebut flavonoid, flavan-3-OLS, atau katekin (catechin meskipun sebenarnya subkelompok flavonoid).

[edit] BiosynthesisMain article: Flavonoid biosynthesis

[edit] Biological rolesFlavonoid tersebar luas pada tanaman memenuhi banyak fungsi.Flavonoid adalah pigmen tumbuhan yang paling penting untuk pewarnaan bunga menghasilkan pigmentasi kuning atau merah / biru di kelopak. Warna-warna itu adalah tujuan untuk menarik hewan penyerbuk.Flavonoid disekresikan oleh akar tanaman inang mereka rhizobia membantu dalam tahap infeksi hubungan simbiosis dengan kacang-kacangan seperti kacang polong, kacang-kacangan, semanggi, dan kedelai. Hidup rhizobia dalam tanah dapat merasakan flavonoid dan ini memicu sekresi faktor Nod, yang pada gilirannya diakui oleh tanaman inang dan dapat menyebabkan akar rambut deformasi dan tanggapan selular beberapa seperti fluks ion dan pembentukan bintil akar .Mereka juga melindungi tanaman dari serangan mikroba, jamur [3] dan serangga..

[edit] Biological activityFlavonoid (khususnya flavonoid seperti katekin) adalah "kelompok yang paling umum dari senyawa polifenol dalam makanan manusia dan ditemukan ubiquitously pada tanaman" [4]. Flavonol, bioflavonoid asli seperti quercetin, juga ditemukan ubiquitously, tetapi lebih rendah

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kuantitas. Kedua set senyawa memiliki bukti kesehatan modulasi efek pada hewan yang memakannya.Distribusi luas flavonoid, berbagai mereka dan toksisitas relatif rendah dibandingkan dengan senyawa tanaman aktif (alkaloid misalnya) berarti bahwa banyak hewan, termasuk manusia, menelan jumlah yang signifikan dalam diet mereka. Flavonoid telah disebut sebagai "pengubah respon biologi alami" karena bukti eksperimental yang kuat kemampuan melekat mereka untuk memodifikasi reaksi tubuh terhadap alergen, virus, dan karsinogen. Mereka menunjukkan anti-alergi, anti-inflamasi [5], anti-mikroba [6] dan aktivitas anti-kankerNew! Click the words above to edit and view alternate translations. Di

[edit] Antioxidant activityFlavonoid (baik flavonol dan flavanol) yang paling sering dikenal karena aktivitas antioksidan secara in vitro.Konsumen dan produsen makanan telah menjadi tertarik pada flavonoid untuk properti yang mungkin mereka obat, terutama peran putatif mereka dalam pencegahan kanker dan penyakit kardiovaskular. Meskipun bukti fisiologis belum dibentuk, efek menguntungkan dari buah, sayuran, dan teh atau bahkan anggur merah telah dikaitkan dengan senyawa flavonoid daripada nutrisi yang dikenal dan vitamin. [8]Atau, penelitian yang dilakukan di Linus Pauling Institute dan dievaluasi oleh Otoritas Keamanan Makanan Eropa menunjukkan bahwa, setelah asupan makanan, flavonoid sendiri yang sedikit atau tidak ada nilai antioksidan langsung [9] [10]. Seperti kondisi tubuh tidak seperti kondisi tabung reaksi terkontrol , flavonoid dan polifenol lainnya yang kurang diserap (kurang dari 5%), dengan sebagian besar dari apa yang diserap dengan cepat dimetabolisme dan dikeluarkan. Peningkatan kapasitas antioksidan darah terlihat setelah konsumsi makanan kaya flavonoid tidak disebabkan langsung oleh flavonoid sendiri, tetapi yang paling mungkin adalah karena tingkat asam urat meningkat yang dihasilkan dari metabolisme flavonoid [11] Menurut Frei., "Kami sekarang dapat mengikuti aktivitas flavonoid dalam tubuh, dan satu hal yang jelas adalah bahwa tubuh melihat mereka sebagai senyawa asing dan sedang berusaha untuk menyingkirkan mereka. "

[edit] Other health benefits

[edit] Cancer

Proses bersiap-siap untuk menyingkirkan senyawa yang tidak diinginkan menyebabkan apa yang disebut enzim fase II yang juga membantu untuk menghilangkan mutagen dan karsinogen, dan karena itu mungkin nilai dalam pencegahan kanker. Flavonoid dapat menginduksi mekanisme yang membantu membunuh sel kanker dan menghambat invasi tumor "[11] UCLA kanker peneliti telah menemukan bahwa peserta studi yang makan makanan yang mengandung flavonoid tertentu tampaknya dilindungi dari mengembangkan kanker paru-paru. Dr Zuo-Feng Zhang, dari. UCLA Jonsson Cancer Center dan profesor kesehatan masyarakat dan epidemiologi di UCLA School of Public Health mengatakan flavonoid yang tampaknya menjadi catechin termasuk paling protektif, ditemukan di stroberi dan teh hijau dan hitam; kaempferol, ditemukan di brussel sprouts dan apel ;. dan quercetin, yang ditemukan dalam kacang-kacangan, bawang dan apel [12]Penelitian mereka juga menunjukkan bahwa hanya sejumlah kecil flavonoid yang diperlukan untuk melihat manfaat medis. Mengambil suplemen makanan besar tidak memberikan manfaat ekstra dan dapat menimbulkan beberapa risiko. [11]

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[edit] Diarrhea

Sebuah studi yang dilakukan di Rumah Sakit Anak & Research Center Oakland, bekerja sama dengan para ilmuwan di Heinrich Heine University di Jerman, telah menunjukkan bahwa epikatekin, quercetin dan luteolin dapat menghambat perkembangan cairan yang mengakibatkan diare dengan menargetkan fibrosis Cl transmembran konduktansi usus kistik regulator -. transportasi menghambat cAMP-merangsang sekresi Cl-dalam usus [13][sunting] agen menstabilkan kapilerBioflavonoid seperti rutin, monoxerutin, diosmin, troxerutin dan hidrosmin memiliki norma vasoprotective.

[edit] Important flavonoids

This article may need to be updated. Please update this article to reflect recent events or newly available information, and remove this template when finished. Please see the talk page for more information. (October 2009)

[edit] QuercetinMain article: quercetin

QuercetinQuercetin adalah flavonoid dan, untuk lebih spesifik, sebuah flavonol. Ini adalah bentuk aglikon dari sejumlah glikosida flavonoid lainnya, seperti rutin dan quercitrin, ditemukan dalam jeruk, soba buah dan bawang. Quercetin membentuk quercitrin glikosida dan rutin bersama dengan rhamnosa dan rutinose, masing-masing. Hal ini juga dapat membantu untuk mencegah beberapa jenis kanker, namun saat ini ada penelitian lebih dibutuhkan di daerah ini.

[edit] Epicatechin

Epicatechin (EC)Epikatekin meningkatkan aliran darah dan dengan demikian tampaknya baik untuk kesehatan jantung. Kakao, bahan utama coklat hitam, berisi jumlah yang relatif tinggi epikatekin dan telah ditemukan memiliki hampir dua kali kandungan antioksidan dari anggur merah dan sampai tiga kali lipat dari teh hijau dalam in-vitro tes. [14] [15] namun dalam tes yang diuraikan di atas sekarang muncul efek antioksidan bermanfaat minimal sebagai antioksidan dengan cepat dikeluarkan dari tubuh.

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[edit] Important dietary sources

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Sumber yang baik dari flavonoid termasuk buah jeruk semua, berry, ginkgo biloba, bawang [16] [17], peterseli [18], (bawang merah terutama [19]) pulsa [20], teh (teh terutama putih dan hijau), merah anggur, seabuckthorn, dan cokelat gelap (dengan kandungan kakao dari tujuh puluh persen atau lebih besar).

[edit] Citrus

Berbagai flavonoid yang ditemukan dalam buah jeruk, termasuk jeruk.Bioflavonoid jeruk hesperidin meliputi (a glikosida dari hesperetin flavanon), quercitrin, rutin (dua glikosida flavonol dari quercetin), dan tangeritin flavon. Selain memiliki aktivitas antioksidan dan kemampuan untuk meningkatkan tingkat intraseluler vitamin C, rutin dan hesperidin memberi efek menguntungkan pada permeabilitas kapiler dan aliran darah. Mereka juga menunjukkan beberapa manfaat anti alergi dan anti-inflamasi dari quercetin. Quercetin juga dapat menghambat reverse transcriptase, bagian dari proses replikasi retrovirus [21] Relevansi terapi inhibisi ini belum ditetapkan.. Hydroxyethylrutosides (DIA) telah digunakan dalam pengobatan permeabilitas kapiler, mudah memar, wasir, dan varises

[edit] Tea

This section does not cite any references or sources.Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (October 2009)

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Bai Hao Yinzhen from Fuding in Fujian Province, widely considered[citation needed] the best grade of white teaFlavonoid teh hijau adalah senyawa antioksidan kuat, pikir untuk mengurangi kejadian kanker dan penyakit jantung. Flavonoid utama dalam teh hijau adalah kaempferol dan catechin (katekin, epikatekin, epikatekin galat (ECG), dan epigallocatechin gallate (EGCG)).Dalam memproduksi teh seperti teh oolong dan teh hitam, daun yang diizinkan untuk mengoksidasi, di mana enzim hadir dalam teh mengubah beberapa atau semua katekin untuk molekul yang lebih besar [kutipan diperlukan]. Namun, teh hijau diproduksi dengan dikukus daun segar-potong, yang inactivates enzim, dan oksidasi tidak signifikan terjadi. Teh putih adalah yang paling diproses dari teh dan ditampilkan [kutipan diperlukan] untuk menyajikan jumlah tertinggi katekin diketahui terjadi di sinensis kamelia.

[edit] WineSee also: Phenolic compounds in wine

ulit anggur mengandung sejumlah besar flavonoid serta polifenol lainnya [22]. Kedua merah dan anggur putih mengandung flavonoid, namun sejak anggur merah diproduksi oleh fermentasi dalam kehadiran kulit anggur, anggur merah telah diamati mengandung kadar flavonoid, dan polyphenolic lain seperti resveratrol

[edit] Dark chocolate

Flavonoid ada secara alami dalam kakao, tetapi karena mereka dapat menjadi pahit, mereka sering dihapus dari coklat, bahkan berbagai gelap [23]. Sementara flavonoid yang hadir dalam coklat susu, penelitian telah menunjukkan bahwa mereka tidak mudah diambil oleh tubuh;. mereka juga tidak mudah diambil ketika coklat gelap dikonsumsi bersama susu [24]

[edit] Subgroups

Lebih dari 5000 flavonoid alami telah ditandai dari berbagai tanaman. Mereka telah diklasifikasikan menurut struktur kimianya, dan biasanya dibagi lagi menjadi sub kelompok berikut (untuk lebih lanjut membaca lihat [25]):

[edit] Flavones

Flavones are divided into four groups:[26]

Group Skeleton Examples

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Description

Functional groups

Structural formula3-

hydroxyl

2,3-dihydr

o

Flav one 2-

phenylchromen-4-one

✗ ✗Luteolin, Apigenin, Tangeritin

Flav on ol or3-

hydroxy flav one

3-hydroxy-2-phenylchrome

n-4-one✓ ✗

Quercetin, Kaempferol, Myricetin, Fisetin, Isorhamnetin, Pachypodol, Rhamnazin

Flav an one 2,3-dihydro-2-phenylchrome

n-4-one✗ ✓

Hesperetin, Naringenin, Eriodictyol, Homoeriodictyol

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Flav an on ol or3-

Hydroxyflavanoneor

2,3-dihydroflavonol

3-hydroxy-2,3-dihydro-2-

phenylchromen-4-one

✓ ✓Taxifolin (or Dihydroquercetin), Dihydrokaempferol

[edit] IsoflavonesIsoflavon menggunakan kerangka 3-phenylchromen-4-satu (tanpa substitusi gugus hidroksil pada karbon pada posisi 2).Contoh: genistein, daidzein, Glycitein

[edit] Flavan-3-ols, Flavan-4-ols, Flavan-3,4-diols, and proanthocyanidins

Flavan structure

Derivatives of flavan.

Skeleton Name

Flavan-3-ol

Flavan-4-ol

Flavan-3,4-diol (leucoanthocyanidin)

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Flavan-3-ols (also known as flavanols) and Proanthocyanidins

Flavan- 3-ols use the 2-phenyl-3,4-dihydro-2H-chromen-3-ol skeleton. Catechins (Catechin (C), Gallocatechin (GC), Catechin 3-gallate (Cg), Gallocatechin 3-gallate (GCg)), Epicatechins (Epicatechin (EC), Epigallocatechin (EGC), Epicatechin 3-gallate (ECg), Epigallocatechin 3-gallate (EGCg))Proanthocyanidins are dimers, trimers, oligomers, or polymers of the flavanols.

[edit] Anthocyanidins

Flavylium skeleton of anthocyanidins Anthocyanidins Anthocyanidins adalah aglycones dari anthocyanin. Anthocyanidins menggunakan

flavylium (2-phenylchromenylium) ion kerangkaContoh: cyanidin, delphinidin, Malvidin, pelargonidin, peonidin, Petunidin

[edit] Availability through microorganisms

Beberapa artikel penelitian terbaru menunjukkan produksi efisien molekul flavonoid dari rekayasa genetik mikroorganisme [27] [28] [29]

MODUL XV

XV. SENYAWA HETEROSIKLIK DAN ASAM NUKLEAT

Senyawa heterosiklik dari senyawa pyrimidin dan purin

Senyawa heterosiklik adalah senyawa organik berbentuk lingar yang tersusun dari 2 atom

atau lebih. Salah satu dari senyawa heterosiklik itu adalah asam nukleat. Asam nukleat

terdiri dari dua macam cincin lingkar yang berbeda yaitu pirimidina dan purin. Primidina

adalah senyawwa lingkar cincin enam yang dua dari anggota cincinnya adalah atom

nitrogen selebihnya adalah atom karbon yang mempunyai struktur seperti berikut :

N

N

150

H pirimidinDan senyawa purin terdiri penggabungan dua senyawa lingkar yang terdiri dari cincin lima

dan enam yang empat dari anggota cincinnya adalah atom nitrogen selebihnya atom

karbon dengan struktur sebagai berikut :

N N

N N

Hpurin

Atom Hidrogen H merupakan pusat reaksi dari baik basa purin maupun basa

pirimidin

Asam nukleat dan nukleotida.

Asam nukleat terdiri dari tiga kompenen yakni gugus basa nukleat ( adenin, guanin

cytosin, uracil, thymin), gugus karbohidrat (ribosa dan deoksi ribosa), dan gugus posfat

( mono, di, tri dan seterusnya). Secara garis besarnya asam nukleat terdiri dari asam ribosa

nukleat (RNA) dan asam deoksi ribosa nukleat, kedua asam nukleat ini berfungsi

memberikan informasi genetik kepada sel makhluk hidup. Penandaan DNA pada suatu sel

ditentukan oleh semua informasi dari sel induk, menegndalikan pertumbuhan suatu sel dan

pembelahan sel., serta perintah biosintesa dari enzim, dan protein-protein lainnya yang

diperlukan untuk semua peran sel.

Seperti protein asam nukleat adalah polimer, enzim katalis hidrolisa yang

memecah asam nukleat menjadi gugus-gugus penyusunnyya yang disebut nulkeotida.

Selanjutnya setiap nukleotida dapat dipecah oleh enzim katalis hidrolisa menghasilkan

nukleosida dan asam posfat H3PO4, dan setiap nukleosida dapat dipecah oleh enzim

katalis hidrolisa menjadi senyawa pentosa sederhana dan senyawa heterosiklik purin dan

pirimidin

Asam nukleat

Nukleotida151

Posfat gula Basa nukleat

H2OEnzim

H3PO4 +

Nukleosida

H3O+

Gula + amina heterosiklik

Komponen gula dalam asam ribosa nukleat adalah ribose dan komponen gula dalam

deoksiribosa nukleat adalah 2’-deoksiribosa. Nama deoksi berasal dari atom oksigen pada

posisi 2’ hilang dari molekul ribose, tanda ‘ pada angka 2 menunjukan posisi atom oksigen

dalam molekul gula nukleotida. Dan nama tanpa tanda ‘ menunjukkan posisi atom oksigen

pada basa amina cincin heterosiklik.

CH2OH OH CH2OH OH H H H H H OH OH OH H

Ribosa 2’ deoksiribosa

Ada dua macam senyawa purin yang taerdapat pada asam nukleat yakni Adenin dan

guanine dengan struktur sebagai berikut :

NH2 O

N N N N

152

gula Basa amina

NH2

N N N N

H H Adenin Guanin

Ada 3 macam senyawa pirimidin yang terdapat pada asam nukleat yakni :

NH2 O OH3C

N N N

N O N O N O

H H H Cytosin Uracil Thymin

Struktur DNA

NH2 O

N N N N

NH2

N N N N

H2PO3CH2 H2PO3CH2

H H H H OH OH OH H

Ribosa 2’ deoksiribos

NH2 O153

H3C N N

H

CH2OH N O CH2OH N O H H H H H OH OH OH H

Ribosa 2’ deoksiribosa

NH2 O

N N N N

NH2

N N N N

H H Adenin Guanin

CH2OH OH CH2OH OH H H H H H OH OH OH H

Ribosa 2’ deoksiibosa154

NH2 O OH3C

N N N

N O N O N O

H H H Cytosin Uracil Thymin

CH2OH OH CH2OH CH2OH H H H H OH OH OH OH H

Ribosa 2’ deoksiribosa

Sintesa DNA

XVI. POLIMER

Polimer adalah senyawa organic bermolekul besar yang teridiri dari unit molekul

monomer yang berulang. Banyaknya pengulangan pada molekul monomer menunjukkan

derajad polimerisasi dari molekul polimer tersebut. Makin banyak unit monomer pada

suatu molekul polimer maka sifat kimianya makin inert. Berdasarkan proses

pembentukanknya secara garis besar polimer dibagi menjadi polimer alami dan polimer

sintetik. Polimer alami adalah protein yang terdiri dari unit monomer asam-asam amino,

pati yang terdiri dari unit monomer heksosa, asam nukleat yang terdiri dari unit monomer

basa nukleat, ribose, dan fosfat. Polimer sintetik adalah polimer yang dibuat dibuat dalam

proses industri kimia, seperti polietilena, polipropilena, polistirena, polivinilklorida, nilon,

polyester, serat akrilat, poliepoksi, resin fwenolat, resin urea formal dehid, dan lain-lain.

Polimer bisa terbentuk melalui proses reaksi addisi dan melalui reaksi kondensasi. Contoh

reaksi polimerisasi addisi adalah sebagai berikut :

O O O

C6H5-C--O-O--C-C6H5 2 C6H5-C-Oo = Ino

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Ino + H2C=CH2 In-H2C=CH2o

Klassifikasi polimer

Polimer Sintetik dapat digolongkan berdasarkan metode sintesa atau pun bisa juga tahap

pembentukan rantai polimer atau tahap pembentukan polimer. Kategori ini mencakup

banayak hal dan memerlukan kegunaan yang berbeda. Tahap pembentukan rantai polimer

disebut polimer addisi dengan istilah lain dihasilkan dengan polimerisasi reaksi berantai

yang inisiatornya teraddisi ke ikatan ganda karbon-karbon untuk menghasilkan senyawa

intermediet yang reakstif. Polimer terbentuk dari banyyaknya monomer yang teraddisi ke

ujung rantai yang reaktif dari rantai yang terbentuk. Inisiator bisa bermula baik anion,

kation, atau radikal, dan polimer yang dihasilkan dengan cara begini hanya mempunyai

atom-atom karbon pada rantai utama. Polietilen dihasilkan dengan reaksi inisiasi

polimerisasi etilen dengan tahap pembentukan polimer sebagai berikut :

Ino + H2C=CH2 In-H2C-CH2o + H2C=CH2

In-H2C-CH2-H2C-CH2o + H2C=CH2 In-H2C-CH2-H2C-CH2-H2C-

CH2o + H2C=CH2 In-H2C-CH2-H2C-CH2-H2C-CH2-H2C-CH2o

Polietilen

Tahap pembentukan polimer yang disebut dengan pertumbuhan polimer kondensasi yang

terbentuk dengan proses polimerisasi dimana tahap pembentukan ikatan terjadi pada reaksi

polar. Reaksi terjadi pada antara dua gugus fungsi molekul, dan sertiap ikatan dalam

polimer terbentuk secara bebas dari yang lainnnya. Polimer biasanya dihasilkan dari dua

monomer yang salling berikatan dan biasanya mempynyai atom lainnya yang teraddisi ke

atom karbon pada rantai utama. Nilon adalah merupakan suatu polimer poliamida yang

terbentuk dari reaksi asam dikarboksilat dan senyawa diamina. Dengan tahap pertumbuhan

sebagai berikut :

H2N-(CH2)6-NH2 + HOOC-(CH2)6-COOH

-NH-(CH2)6-NH-CO-(CH2)6-CO- + H2O Nilon 66

Reaksi polimerisasi radikal, kationik dan anionic

156

Beberapa polimer alkena berberat molekul rendah mengalami reaksi polimerisasi yang cepat

ketika berkontak dengan sejumlah inisiator radikal. Polietilen adalah salah satu molekul

polimer berantai pertama yang dibuat diindustri secara komersil yang sederhana yang telah

diproduksi semenjak tahun 1943. Produksi tahunan untuk polimer ini dengan volume produksi

hampir 12 juta ton. Reaksi polimerisasi propilena biasanya berlangsung pada tekanan 1000 –

3000 atm dan suhu tinggi 100 – 250 oC. Dengan katalis radikal benzoil peroksida, jumlah unit

monomer bisa dari beberapa ratus sampai beberapa ribu unit rantai monomer. Semua reaksi

radikal berantai berlangsung dalam tiga macam tahap reaksi yakni tahap inisiasi, tahap

propagasi, dan tahap terminasi.

Inisiasi bermula ketika terbentuk sejumlah radikal yang dibentuk oleh katalis. Salah satu

dari radikal ini teraddisi ke molekul etilena membentuk rantai karbon radikal baru,

polimerisasi berlangsung terus menerus.

Ino + H2C=CH2 In-H2C-CH2o + H2C=CH2

In-H2C-CH2-H2C-CH2o + H2C=CH2 In-H2C-CH2-H2C-CH2-H2C-

CH2o + H2C=CH2 In-H2C-CH2-H2C-CH2-H2C-CH2-H2C-CH2o Polietilen

Reaksi polimerisasi polipropilena terjadi dalam lima tahap berikut :

Tahap 1 ( inisiasi )

O O O

C6H5-C--O-O--C-C6H5 2 C6H5-C-Oo = Ino

Tahap 2 Ino + H3C-HC=CH2 In-HC-CH2o

H3C

Tahap 3 ( propagasi )

In-HC-CH2o + H3C-HC=CH2 In-HC-CH2-CH-CH2o

H3C H3C H3C

In- -H2C-CH2-HC-CH2o + n H3C-H2C=CH2 In-(HC-CH2-)n-HC-CH2o

H3C H3C H3C H3C

157

Tahap 4 (Quenching)

In- (HC-CH2-)nHC-CH2o + In-(HC-CH2-)n-HC-CH2o

H3C H3C H3C H3C

In-H2C-CH2-HC-CH2-CH2-CH-n(CH2-HC-)-In

H3C H3C H3C H3C

Tahap 5 ( terminasi )

In- (HC-CH2-)nHC-CH2o + In-(HC-CH2-)m-HC-CH2o

H3C H3C H3C H3C

-(H2C-CH2-)n-HC-CH2-CH2-CH-n(CH2-HC-)m-

H3C H3C H3C H3C

Reaksi polimerisasi kationik

Senyawa turunan monomer alkena tertentu dapat dipolimerisasi dengan mekanisme reaksi

polimerisasi kationik, dan juga dengan mekanisme reaksi radikal. Reaksi polimerisasi kationik

terjadi dengan jalur reaksi berantai dan memmerlukan proton yang kuat atau asam Lewis

sebagai inisiator. Reaksi berantai ini terjadi melalui reaksi addisi elektrofilik dari karbokation

intermediet ke ikatan ganda karbon-karbon dari unit monomer lainnya

Tahap 1 (inisiasi)

H+ + S-HC=CH2 +HC-CH3

STahap 2 ( propagasi )

+HC-CH3 + SHC=CH2 H3C-CH-CH2-CH+

S S S

158

H3C-CH-H2C-CH+ + n S-H2C=CH2 (H3C-CH-)n-H2C-CH+

S S S S

Tahap 4 (Quenching)

(H3C-CH+-)n + OH- (-CH2-CH-)n + H2O

. S S

Tahap 5 ( terminasi )

I (-+CH-CH3)n- - H+ (-CH-CH2-)n

S S

-(H2C-CH2-)n-HC-CH2-CH2-CH-n(CH2-HC-)-

H3C H3C H3C H3C

Dimana Nu = inisiator nukleofilik, S = substituen gugus penarik electron

Reaksi polimerisasi anionic

Monomer alkena yang mengandung substituen gugus penarik electron dapat dipoolimerisasi dengan katalis anionic. Reaksi berantai dapat terjadi dimana tahap yang paling menentukan reaksi adalah tahap addisi nukleofil dari anion ke monomer tak jenuh. Contohnya

H2C=CH + Nu:- Nu-CH2-CH:- + H2C=CH Nu-CH2CH-H2C-CH:-

S S S S S

- (-CH2-CH-)n-

S

Tahap 1 (inisiasi)

Nu:- + S-HC=CH2 -:HC-CH2-Nu

S

Tahap 2 ( propagasi )

-:HC-CH2 -Nu + SHC=CH2 -:HC-CH2-CH2-CH-Nu159

S S S

-:HC-CH2-HC-CH2-Nu + n S-H2C=CH2 -:(-HC-CH2-)n-HC-CH2-Nu

S S S S

Tahap 4 (Quenching)

-:(HC-CH2-)n + H+ (-CH2-CH-)n + H2O

. S S

Tahap 5 ( terminasi )

Nu:- (-CH-CH2-)n - Nu:- (-CH-CH2-)n

S S

Monomer akrinlonitril (H2C=CHCN), methyl methakrilat (H2C=C(CH3)COOCH3, dan stirena (H2C=CHC6H5) semuanya dapat mengalami reaksi polimerisasi anionic, meskipun diperlukan radikal sebagai inisiator polimerisasi untuk produksi skala komersil.Salah satu contoh yang paling menarik dari reaksi polimerisasi anionic adalah super glue satu tetesnya mempunyai daya rekat 2000 lb. Super glue adalah salah satu contoh produk yangpaling sederhana dari rekasi polimerisasi anionic dari bahan murni metal a-sianokrilat. Karena ikatan ganda karbon mempunyai dua gugus penarik electron, sehingga reaksi addisi anionic dapat berlangsung dengan mudah dan cepat. Dengan adanya sediit air atau basa pada permukaan bahan sudah cukup untuk memulai reaksi polimerisasi sianokrilat dan selanjutnya terjadi penggabungan antar molekul monomer. Kulit adalah sumber yang terbaik dari inisiator dasar yang diperlukan, dan banyak orang menemukan jarinya lengket setelah menyentuh super glue.

CN CN

H2C=C-COOCH3 + -OH HO-CH2-C:- siano akrilat

COOCH3

CN

-CH2-C

COOCH3 n

160

Super glue

Stereokimia dari polimer

Secara garis besarnta polimer mempunyai tiga bentuk stereokimia

Isotactic

H3C H H3C H H3C H H3C H H3C H

Syndiotactic

H3C H H H3C H3C H H H3C H3C

Atactic

H3C H CH3 H H3C H H CH3 H H3C

Polimerisasi diena ( karet alam dan karet sintetis )kopolimerPolimer nilonPolimer poli uretahn

hubungna Struktur dan kimia polimerhubungan Struktur dan sifat fisika polimer

Klassifikasi polimer sinthetik berdasarkan sifat fisikanya yang dapat digunakan untuk menetukan hubungan sifat fisika dengan struktur polimer. Pada dasarnya penggolongan polimer berdasarkan sifat fisikanya dapat digolongkan menjadi empat golongan bedar yakni a. thermoplastic.Menurut kebanyakan orang mengira polimer adalah thermoplastic sebagai plastic. Polimer ini keras pada suhu kamar dan lunak dan meleleh bila dipanaskan.

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Thermoplastik ini bisa dibuat menjadi mainan anak-anak, alat tidur, telefon, atau beribu-ribu jenis produk lainnya. Karena thermopalstik tidak mempunyai ikatan silang, maka masing-masing molekul dapat bergeser satu sama lainnya bila dipanaskan. Beberapa produk polimer thermoplastic seperti polimetilmetakrilat, yang digunakan sebagai pleksi glass adalah amorf, sedangkan yang lainnya seperti nilon dan poli etilen adalah kristal.b. Fiber.Fiber adalah serat tipis yang dihasilkan dari ekstruding dan pelelehan polimer melalui lobang yang halus pada pemintalan serat, kemudian serat didinginkan dan dipintal. Pengaliran menyebabkan polimer ini mempunyai oreantasi bentuk kristal sepanjang gulunngan fiber, proses ini mengakibatkan penguatan batas kekuatan tarik polimer. Beberapa jenis produk polimer yang tergolong semi kristal adalah nilon, dacron, dan poli etilen.c. ElastomerElastomer adalah polimet yang bersifat amorf mempunyai kemampuan memanjang dan mengkerut menjadi bentuk awalnya kembali. Polimer-polimer ini dapat membentuk ikatan silang untuk mencegah pergeseran antar molekul antara stu sama lainnya. Ranntai molekulnya tak beraturan untuk mencegah pembentukan kristal yang kaku. Bila ditarik rantai lurus yang tersusun secara random akan menjadi melar sesuai dengan arah tarikan Gaya Van der Waals yang bekerja terlalu lemah dan sedikit sekali terjadi yang bisa mempertahankan oreantasi ini, akan tetapi dengan adanya elastomer akan sulit membentuk kumparan yang tersusun secara random bila dilakukan penarikan. Karet alam adalah salah satu contoh elastomer. Karet alam mempunyai rantai yang panjang dan terjadi ikatan silang secara elektrostatik, akan tetapi dengan geometri tak beraturan sulit untuk terjadinya bentuk kristal. Sebaliknya Getta percha adalah polimer kristalin yang tinggi bukan elastomer.

d. Resin thermosetting.Resin thermosetting adalah polimer yang banyak berikatan silang dan memadat sampai menjadi keras, berupa massa yang tak larut bila dipanaskan. Balelit adalah salah satu contoh resin thermosetting yang pertama kali diproduksi tahun 1907 oleh Leo Baekeland, yang telah banyak diperdagangkan dalam waktu yang lama dari pada polimer sintetik lainnya. Bakelit banyak sekali digunakan dalam bentuk cairan kental untuk perekat, pelapis, dan bahkan dipakai untuk keperluan suhu tinggi seperti ujung peluru kendali. Secara kimia bakelit adalah resin fenolik yang dihasilkan dari reaksi fenol dan formal dehid. Pada saat pemanasan molekul air dibebaskan, terbentuklah beberapa ikatan silang, dan polimer berubah menjadi bentuk yang paling stabil yakni berupa massa seperti bebatuan. Ikatan silang pada bakelit dan bahan thermosetting lainnya adalah bentuk tiga dimensi dan sangan rumit, sehingga tidak bisa digambarkan bentuk rantai polimernya. Bakelit adalah molekul yang sangat besar sekali.

OH OH

H+

+ H-C=O

H HO

Fenol formal dehid OH OH

162

OH OH

Resin fenol formal dehid ( bakelit )

Daftar pustaka :

1. John Mc. Murry “ Organic chemistry “ Brooks/cole Publ. Co. 1984.

2. L. F. Fhiser “ Organic Chemistry “ Mazen Co. Ltd 1957

3. R.T. Morrison and N. Boyd. “ Organic chemistry “ 3rd ed Prentice Hall Publ. Co. 1978.

4. T. A. Geissman “ Principles of organic chemistry” 3rd ed 1968 W.H. Freeman and

Company. (pp 1 - 886)

5. R. F. Brown “Organic Cemistry” 1975, Wadworth Publ. Co. (pp 1 – 995)

6. H. Meislich et al. “ Organic Chemistry” Schaum’s outlineseries 1977.

7. "http://en.wikibooks.org/wiki/Organic_Chemistry/Overview_of_Functional_Groups"

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