Giáo trình Hóa học hữu cơ - Đinh Văn Hùng

8/3/2019 Gio trnh Ha hc hu c - inh Vn Hng

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Trngi hc Nng nghip H Ni - - Gio trnh Ho hu c..11

B gio dc v o toTrng i hc nng nghip I - H Ni

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inh vn hng - trn vn chin

Pgs.ts. inh vn hng (Ch bin)

Gio trnh

Ho hc hu c

Nm 2007


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Li ni u

Gio trnh ho hu c ny c bin son theo cng mn hc chnh thc dng chokhi ngnh Nng- Lm- Ng nghip do b mn ho trng i hc Nng nghip I ch tr v c hi ng khi ngnh thng qua. Gio trnh nhm cung cp cho sinh vin nhng kin thc cbn v Ho hu c.

Trng tm ca gio trnh l cu to v tnh cht ca cc hp cht hu c, cu to v tnh chtca mt s loi hp cht t nhin c lin quan nhiu n cc mn hc c s v chuyn mn cakhi ngnh.

Tuy nhin, do thi lng mn hc rt t (2 VH), nn chng ti ci tin chng mc saocho gn nht. Cng chnh v vy khng trnh khi sai st khi bin son. chng ti rt mong nhnc nhng kin ng gp ca bn c v ng nghip gio trnh c hon thin hn choln ti bn sau.

H Ni, 2007

Cc tc gi


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Chng I.

i cng

Xa kia, ngi ta khng phn bit cht v c v cht hu c, mc d t thi c i ng i ta bit dng v sn xut mt s cht hu c nh ngi n bit ly ng t ma, bit lychm t cy chm; ngi Ai Cp bit ly tinh du thm, cho ln men nc ngt thnh ru. Cngchnh v vy, khi ngi ta cha phn bit ha hc v c v ha hc hu c.

S pht trin ca ha hc hu c bt u t th k XVII, khi cc hp cht ly t cy ci vng vt c a vo nghin cu. n gia th k XVIII, trn c s phn ng t chy ngi ta xc nh c cacbon, hiro, nit, oxi c trong cc hp cht tch t ng vt v thc vt, t ha hc hu c thc s bt u pht trin. Khi nim ha hc hu c do Beczeliuyt (Bezelius) xut nm 1807. ng cho rng c th sinh vt l xng ha hc, c b phn ring bit snxut cc sn phm quan trng cho s sng.

Nm 1824 Vuele (Wohler) tng hp c axit oxalic (H2C2O4) t xianogen (C2N2) vnm 1828 ng cng tng hp c ur (H2N-CO-NH2) t amoni xianat (H4NOCN). Tip sau hng lot cc cng trnh mi c cng b, k c cc cng trnh tng hp cc hp cht hu ckhng tch c t t nhin. n u th k XIX ngi ta khng nh rng cacbon l thnhphn c bn khng th thiu c trong cc hp cht hu c. Ngi ta a ra nh ngha:

Ho hc hu c l hc thuyt v ho hc ca cc hp cht ca cacbon.

Trn c s nghin cu cc c im cu to chung ca cc hp cht hu c, Soolemme(Soorlemmer) v mt s tc gi nh ngha:

Ho hc hu c l ngnh ho hc ca hirocacbon v cc dn xut ca chng.

Cho n nay c hai nh ngha trn vn c cng nhn.

S pht trin ca ho hc hu c khng nhng c tc dng trc tip n cc ngnh kinh tquc dn c lin quan n ho hc hu c, m cn nh hng su sc n cc ngnh khoa hckhc nh sinh hc, ho sinh, y hc, dc hc, nng nghip ...lm cho con ngi ngy cng lmch thin nhin v bt thin nhin, iu khin thin nhin phc v i sng con ngi.

Ho hc hu c l ho hc v nhng hp cht ca cacbon. i tng nghin cu ca mnhc ny l cc hirocacbon v cc dn xut ca chng. i tng ny c kho st ring l do

mt s nguyn nhn sau y:

- S lng cc hp cht hu c rt ln v tng rt nhanh. Khong trn 10 triu hp cht huc c bit. Trong c nhng hp cht ng vai tr v cng quan trng i vi cc qutrnh hot ng sng ca c th sinh vt nh cc hp cht gluxit, cc hp cht protein, cc axitnucleic, cc vitamin, cc hocmon

- Vai tr to ln v ng dng phong ph ca ho hc hu c trong i sng hng ngy vtrong cc ngnh kinh t quc dn: Nhin liu v du nhn, cc loi nng dc, thuc cha bnh,cc cht hot ng b mt, cc cht mu v phm nhum


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- i vi cc ngnh sinh hc ni chung v cc ngnh Nng-Lm-Ng ni ring, ho hchu c c coi nh l mn hc c s nghin cu cc quy lut v c ch ca cc qu trnhchuyn ho cc cht trong c th, t c th ra nhng bin php k thut thch hp tc nglm tng nng sut, cht lng ca cy trng v vt nui.

1. Cu to v c im ca Cacbon

Nh trn ni, ho hc hu c l ngnh ho hc dnh ring cho nguyn t cacbon. Slng cc hp cht hu c rt nhiu v ngy cng c tng ln rt nhanh bi nhng hp cht mitm c trong th gii t nhin v bng con ng tng hp trong cc phng th nghim.

Vn t ra l ti sao nguyn t cacbon li c kh nng hnh thnh nhiu hp cht nnh vy? Mun gii quyt vn ny trc ht chng ta nghin cu cu to v c im canguyn t cacbon.

Cacbon l nguyn t thuc chu k hai, phn nhm chnh nhm bn ca bng h thng tunhon. Lp v in t ca n c 6 in t c chia thnh 2 lp : lp trong c 2 in t ( 1s 2); lpngoi c 4 in t ( 2s22p2).

1s2 2s2 2p2

Cc lp in t s v p s to nn nhng m my in t (obitan) khc nhau. Obitan s cdng hnh cu. Cc obitan p c dng s 8 ni. Cc obitan p phn chia trong khng gian theo 3chiu px, py v pz.

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S phn b in t trn cc obitan nh vy chnh l cu to ca nguyn t cacbon trngthi c bn hay trng thi tnh. trng thi ny, cacbon c 2 in t c thn (2p2), do vy ta cth ngh rng cacbon c ho tr 2.



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Thc t th trong cc hp cht hu c, cacbon bao gi cng c ho tr 4. iu ny c th giithch c trn c s thuyt lng t. Theo quan nim ca thuyt ny, trc khi to thnh cc linkt, di tc dng ca nng lng, mt in t phn lp 2s s c kch thch chuyn lnphn lp 2p :

1s2 2s2 2p2 1s2 2s1 2p3

Nng lng cn thit dng cho qu trnh ny gi l nng lng kch thch v n s cb li sau khi hnh thnh lin kt.

trng thi kch thch, nguyn t cacbon c 4 in t c thn, v th cacbon c ho tr 4.

Bn in t c thn ca cacbon c phn b hai trng thi khc nhau v mt nnglng. Mt in t 2s trng thi nng lng thp hn, kh nng i vo lin kt kh hn. Ba int 2p tn ti trng thi nng lng cao hn, kh nng i vo lin kt d dng hn. Do vy, mttrong bn lin kt ca cacbon to bi in t 2s phi khc vi ba lin kt cn li to bi cc int 2p.

Tuy nhin, trong thc t ho hc hu c li khc. Ngi ta gp cc hp cht hu c, trong bn lin kt ca nguyn t cacbon hon ton ging nhau.

gii thch vn ny ngi ta cho rng, obitan 2s trn ln vi cc obitan 2p tothnh cc obitan mi c nng lng v hnh dng khng gian ging nhau. l s lai ho (haycn gi l s lai to) ca cc obitan.

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Hnh dng ca obitan lai ho

Trong cc hp cht hu c, nguyn t cacbon c th tham gia vo ba trng thi lai ho khcnhau.

Lai ho sp

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hay lai ho t din : trng thi ny, mt obitan 2s trn ln vi ba obitan 2p c bn obitan lai ho ging ht nhau hng v bn nh ca mt hnh t din u. Trc cacc obitan lai ho to vi nhau nhng gc bng nhau v bng 109028 (gc ho tr). y chnh lgc ho tr bn vng nht ca nguyn t cacbon.

Trng thi lai ho sp3 l c s gii thch khi nim ca L Ben v Van Hp (1874) v thuytt din ca nguyn t cacbon. Trng thi lai ho sp 3 gp trong cc hp cht no, trong mi linkt gia nguyn t cacbon vi nguyn t ca nguyn t khc hoc vi chnh nguyn t cacbon lnhng mi lin kt n (ni n).



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Lai ho sp2 hay lai ho tam gic: trng thi ny, obitan 2s trn ln vi hai obitan 2p tothnh ba obitan lai ho. Ba obitan lai ho ny nm trn cng mt mt phng v trc ca chng tovi nhau nhng gc 1200. trng thi lai ho sp2 nguyn t cacbon cn li mt in t 2p khngtham gia vo s lai ho, trc ca n vung gc vi mt phng cha ba obitan lai ho. n t p

ny s tham gia vo s hnh thnh lin kt cng vi cc in t p ca cc nguyn t cacbon bncnh. Trng thi lai ho sp2 thng gp trong cc hp cht cha lin kt i (ni i).

Lai ho sp hay lai ho ng thng : trng thi ny, obitan 2s trn ln vi mt obitan 2p c hai obitan lai ho ging ht nhau. Hai obitan ny cng nm trn mt mt phng v trcca chng to vi nhau gc 1800. trng thi lai ho sp, nguyn t cacbon cn hai obitan pkhng tham gia vo s lai ho. Cng ging nh in t p trng thi lai ho sp2, cc in t p nys tham gia vo s hnh thnh cc lin kt . Trng thi lai ho sp thng gp trong cc hp chtcha lin kt ba (ni ba).

Di y m t hnh dng v s phn b m my in t cc trng thi lai ho khc

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Lai ho sp3 Lai ho sp2 Lai ho sp

Nh vy nguyn t cacbon ho tr bn l vin gch xy dng nn ton b ho hu c cuto. Tr mt vi ngoi l, ta c th biu din nhng hp cht ca cacbon bng nhng cng thctrong cacbon c bn lin kt cng ho tr (bt k l nguyn t cacbon lin kt vi nguyn tcacbon hay nguyn t ca nguyn t khc).

biu din cng thc ca cc hp cht hu c, ngy nay ngi ta thng dng cng thccu to, trong quy c rng mt vch ni lin cc k hiu nguyn t tng trng cho mt linkt n, hai vch cho mt lin kt i v ba vch cho mt lin kt ba.

Cch hay c dng nht l biu din di dng cng thc na cu to. Cch ny cho phptit kim ch v thi gian, nhng ng thi cng kh r rng:CH4 CH3-CH3 CH2=CH2 CHCHmetan etan etylen axetylen

H2C

H2CC

CH2

CH2CH2

H2

HC

HCC

CH

CHCH

H

CH3 -CH2 -OH

xiclohexan benzen ancol etylic



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OHCH3CH3 -O -CH3 CH3 -C =O CH3 -C =O imetyl ete axeton axit axetic

Khc vi cc nguyn t khc, ngoi kh nng c th tham gia vo c ba trng thi lai ho sau hnh thnh nn cc lin kt khc nhau, nguyn t cacbon cn c nhng c im m ccnguyn t khc khng c c lm tng kh nng hnh thnh cc hp cht khc nhau, lm chos lng cc hp cht hu c rt ln. Nhng c im l cc nguyn t cacbon c kh nngkt hp vi nhau to thnh mch, trong lin kt cacbon- cacbon rt bn. Mch cacbon cth l mch khng phn nhnh (mch thng), mch phn nhnh hoc mch vng. Nhng mch c th rt ngn ch gm vi nguyn t cacbon ni vi nhau, nhng cng c th rt di, bao gmhng trm, hng ngn nguyn t:

- C - C - C - C - - C - C - C -

- C -

C C

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mch khng phn nhnh mch phn nhnh mch vng

Khi to thnh mch, cc nguyn t cacbon lin kt vi nhau. Cc nguyn t cacbon umch ch lin kt trc tip vi mt nguyn t cacbon khc, cc nguyn t cacbon gia mch cth lin kt vi hai, ba hoc bn nguyn t cacbon khc. Tu thuc s lin kt m mt nguyn tcacbonn lin kt trc tip vi cc nguyn t cacbon khc, ngi ta phn bit thnh cacbonbc 1, cacbon bc 2, cacbon bc 3 hoc cacbon bc 4. Th d, trong phn t etan:

CH3- CH3

hai nguyn t cacbon u l bc 1, bi v mi nguyn t cacbon trong ch c lin kt trctip vi mt nguyn t cacbon khc. Trong phn t propan:

1 2 3CH3- CH2- CH3

cc nguyn t cacbon s 1 v s 3 l cacbon bc 1 do chng ch lin kt trc tip vi mt nguynt cacbon khc. Nguyn t cacbon s 2 l cacbon bc 2 v n lin kt trc tip vi hai nguyn tcacbon s 1 v s 3. Trong phn t isobutan:

1 2 3CH3- CH- CH3

CH3nguyn t cacbon s 2 l cacbon bc 3 v n lin kt trc tip vi ba nguyn t cacbon khc.Tng t nhvy chng ta c th d dng nhn thy, trong phn t neopentan:


CH3

CH3- C- CH3CH3

nguyn t cacbon s 2 l cacbon bc 4.


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Kh nng phn ng ca cc nguyn t lin kt vi cc nguyn t cacbon c bc khc nhaus khc nhau. V vy, vic nhn bit bc ca cc nguyn t cacbon cho php phn on c khnng phn ng ca cc phn t hp cht hu c. iu ny s c chng ta cp ti ccchng sau.

2. lin kt ho hc trong cc hp cht hu c

Nguyn t ca cc nguyn t, tr cc kh tr, u c th phn ng vi nhau to nn phnt, tc l lin kt vi nhau to nn cc hp cht. Ni mt cch khc, cc nguyn t u ckhuynh hng bo ho lp v in t ngoi cng tr thnh lp v in t bn vng (lp v cakh tr).

C nhiu kiu lin kt ho hc vi nhng c im khc nhau: lin kt ion, lin kt cngho tr, lin kt phi tr, lin kt hiro, lin kt kim loi...cc loi lin kt ny u c nghincu trong mn c s l thuyt ho hc.

Trong cc loi lin kt trn, lin kt cng ho tr l ph bin v quan trng nht i vi cchp cht hu c. V vy chng ta nhc li mt s im c bn v loi lin kt ny.

2.1. lin kt cng ho tr

Lin kt ho hc thc hin bng nhng cp in t dng chung gi l lin kt cng ho tr.Cp in t dng chung ny tt nhin phi c spin ngc chiu nhau v khi n thuc v c hainguyn t.

Theo quan im hin i th lin kt ho hc c hnh thnh khi c s xen ph ti a cahai obitan nguyn t. Obitan xen ph nhau nhn c khi y gi l obitan phn t.

Tu theo kiu xen ph ca cc obitan nguyn t, ngi ta phn bit lin kt cng ho trthnh lin kt xicma () v lin kt pi ().

a. Lin kt

Lin kt l lin kt m cc obitan nguyn t xen ph nhau theo kiu ni ui. Obitanphn t bao quanh trc ni hai nhn nguyn t. Lin kt c th to bi cc obitan nguyn t svi s, s vi p, p vi p hoc sp3, sp2, sp vi nhau.

Di y gii thiu s phn b mt in t khi to thnh lin kt gia hiro-hiro,gia cacbon-hiro v gia cacbon-cacbon.

HH H CC C

Lin ktgia H-H, H-C, C-C



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Vng xen ph ca cc obitan nguyn t l cc i, do vy lin kt l loi lin kt bnvng.

Lin kt c i xng trc, do vy hai nguyn t hoc nhm nguyn t c th quay tng

i t do quanh trc i xng lm xut hin cc cu dng khc nhau trong mt s hp cht huc.

b. Lin kt

Lin kt l lin kt m cc obitan nguyn t xen ph nhau theo kiu cnh sn. Obitanphn t i xng nhau qua mt phng nt (mt phng cha trc ni hai nhn nguyn t v vunggc vi trc ca obitan nguyn t).

Lin kt ch to thnh gia hai obitan p vi nhau, p vi d hoc d vi d. Hnh di dy l s phn b mt in t ca lin kt to bi cc obitan nguyn t p.

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C C

S phn b mt in t ca lin kt

Cc obitan nguyn t xen ph nhau t, do vy cc lin kt thng km bn, d b ph v

tham gia trong cc phn ng ho hc.

Lin kt khng c i xng trc, do vy cc nhm th khng c kh nng quay t do xungquanh trc i xng. y chnh l nguyn nhn lm xut hin ng phn hnh hc cis- trans trongcc hp cht c ni i C=C.

Trong cc hp cht hu c, lin kt c thc hin gia hai nguyn t cacbon vi nhaunh trong cc hp cht hu c cha no cha lin kt i v lin kt ba:

C = C C = C

gia cacbon v nguyn t ca nguyn t khc nh oxi, nit...

C = O C = NC = NH

Trng hp cc lin kt hnh thnh gia hai nguyn t ca hai nguyn t c m inchnh lch nhau th n s b phn cc.



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Th d:

C = O+

nhng hp cht c lin kt i lin hp, chng hn nh trong phn t butaien (CH2=CH-CH=CH2), cc in t linh ng, chng thng c gii to trn ton b mch lin hp lm chocc hp cht thuc loi ny thng c nhng tnh cht c bit so vi cc hp cht cha ni ibnh thng.

c. Mt s c im ca lin kt cng ho tr

Lin kt cng ho tr c mt s c tnh khc vi nhng loi lin kt khc:

- di lin kt

Bng thc nghim ngi ta xc nh c rng, khong cch gia hai ht nhn nguyn ttrong lin kt cng ho tr l mt i lng khng i. Khong cch c gi l di linkt. di lin kt thng c k hiu l d, n v tnh bng angxtron (A0) hay nanomet (nm)(1nm = 10A0; 1A0 = 10-8cm).

di lin kt khng phi l tng bn knh ca hai nguyn t, m l tng b n knh cng hotr ca hai nguyn t lin kt vi nhau.

Bit bn knh cng ho tr ca nguyn t ta c th tnh c mt cch gn ng di linkt. Th d, bn knh ca nguyn t hiro l 0,54A 0, bn knh cng ho tr ca n l 0,37A0, th di lin kt H-H l 0,37A0

+0,37A0 = 0,74A0, ch khng phi l 0,54A0 + 0,54A0 = 1,08A0.

Nh vy khi to thnh phn t hiro c s xen ph nhau gia hai obitan 1s ca hainguyn t hiro.

Cc cng trnh nghin cu chng t rng, s xen ph gia hai nguyn t cng nhiu, di lin kt cng ngn, lin kt cng bn, cng kh b ph v. Song, di lin kt khng phi li lng c bn nh gi s bn vng ca mt lin kt ho hc.

- phn cc ca lin kt

Trong lin kt cng ho tr, nu obitan phn t c cu to cn i, ngha l mt in t

ca obitan phn t phn b u gia hai ht nhn, trng tm in tch dng v m trng nhau thlin kt l khng phn cc.

Lin kt cng ho tr khng phn cc ch to thnh gia hai nguyn t ca cng mt nguynt. Th d, lin kt H- H trong phn t H2, lin kt Cl- Cl trong phn t Cl2, lin kt C- C trongphn t CH3- CH3 v CCl3- CCl3...l nhng lin kt cng ho tr khng phn cc.

Trong trng hp nu obitan phn t c cu to khng cn i, ngha l mt in t caobitan phn t lch v pha mt trong hai nguyn t th lin kt cng ho tr l phn cc.



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Lin kt cng ho tr phn cc to thnh do cc nguyn t c m in khc nhau lin ktvi nhau. Khi y, mt in t ca obitan phn t s lch v pha nguyn t no c m inln hn, lm cho nguyn t giu in t hn, tc n mang mt phn in tch m (k hiu -).Ngc li, nguyn t kia ngho in t hn, mang mt phn in tch dng (k hiu +). Nh

vy, trng tm in tch d

ng v m khng trng nhau, m cch nhau mt khong l no . Thd, trong lin kt C- F, flo c m in l 4, cn ca cacbon l 2,5, ngha l flo c m inln hn, lin kt C- F b phn cc v pha nguyn t flo, flo mang mt phn in tch m, cncacbon mang mt phn in tch dng:

c trng cho lin kt cng ho tr phn cc ngi ta dng i lng mmen lng cc,k hiu l muy (). Mmen c tnh bng cng thc:

= e.l

e l in tch in t

l l di lng cc (khong cch gi cc trng tm in tch dng v m)

n v ca mmen lng cc l bai (D) hay culong.met (C.m), 1C.m = 3.1029 D.

Th d, mmen lng cc ca mt vi lin kt nh sau: C- C = 0, C- H = 0,4D, C- N=1,2D,C- O =1,6D, C- Cl =2,3D. Mmen lng cc c trng cho phn cc ca lin kt cng ho tr.Lin kt khng phn cc c = 0, lin kt phn cc c 0. Mmen lng cc cng ln linkt cng phn cc v ngc li. Ni chung, lin kt cng phn cc, cng km bn, cng d b phv trong qu trnh tham gia phn ng. Song, cng c kh nhiu trng hp ngoi l. Trong nhngtrng hp , ngi ta phi xt ti kh phn cc ca lin kt hay ng hn l xt ti nnglng lin kt.

phn cc ca lin kt quyt nh trc ht bi m in ca cc nguyn t lin kt vinhau. Hai nguyn t c m in chnh lch nhau cng ln lin kt vi nhau th lin kt y cngphn cc v ngc li.

Cn ch thm rng, i lng mmen lng cc khng phi l i lng c nh m nthay i do nh hng ca cc nguyn t hoc nhm nguyn t trong phn t, nh hng ca mitrng. phn cc ca lin kt C- H cn ph thuc vo trng thi lai ho ca nguyn t cacbon.

Th du, Csp3-H =0,307D (metan), Csp2-H =0,629D (etylen), Csp-H =0,754D (axetilen)

2.2. Nng lng lin kt

Trong qu trnh hnh thnh phn t cc cht t cc nguyn t t do c s gii phng nnglng. Nng lng gi l nng lng nguyn t v c tnh bng Kcal/mol.

Vy nng lng nguyn t hnh thnh phn t l nng lng gii phng ra khi hnh thnhmt phn t gam cht t cc nguyn t t do iu kin tiu chun.


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Th d, khi to thnh mt phn t gam HCl t cc nguyn t t do H v Cl gii phng ra mtnng lng 102 Kcal/mol, nn nng lng nguyn t hnh thnh phn t bng 102 Kcal/mol.

i vi phn t hai nguyn t th nng lng nguyn t hnh thnh phn t cng chnh lnng lng lin kt.

Vy nng lng lin kt chnh l nng lng cn thit ph v lin kt . Nng lnglin kt cng nh, lin kt cng km bn, cng d b ph v v ngc li.

i vi phn t nhiu nguyn t nh CH4, C2H6... ngi ta dng khi nim nng lng linkt trung bnh bi v trong phn t nhiu nguyn t d rng gm nhng lin kt ging nhau, cclin kt vn c nng lng lin kt khc nhau tu theo th t hnh thnh trc hoc sau. Thd, trong phn t metan (CH4) c 4 lin kt C-H. Lin kt th nht c nng lng 102 Kcal/mol,lin kt th hai l 83 Kcal/mol, lin kt th ba l 128 Kcal/mol, lin kt th t l 80 Kcal/mol. Dovy nng lng nguyn t hnh thnh phn t CH4 l 102 + 83 + 128 + 80 = 393 Kcal/mol. Nnglng lin kt trung bnh ca lin kt C- H l 393:4 = 98,25 Kcal/mol.

3. Phn loi cc hp cht hu c v phn ng hu c

3.1.Phn loi cc hp cht hu c

Theo cch phn loi ph bin nht, cc hp cht hu c c phn thnh dy cc hp chtkhng vng v dy cc hp cht vng. Mi dy li c phn chia thnh nhng nhm v nhngphn nhm nh hn, m ta c th hnh dung bng s tm tt sau y:

Cc hp cht hu c

Cc hp cht khng vng Cc hp cht vng

No Khng no Cc hp cht Cc hp chtng vng d vng

Cc hp cht Cc hp cht D vng D vng

vng khng thm vng thm khng thm thm

No Khng no No Khng no

H thng phn loi trn y ly hirocacbon hoc hp cht d vng n gin nht lm hpcht c s. Nu ta thay th nguyn t hiro ca hp cht c s bng mt nguyn t hoc nhm



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nguyn t khc ta s c cc hp cht c nhm nh chc. Mi nhm nh chc ny li cchia thnh cc phn nhm theo mch khng vng, mch vng...

3.2. Phn loi cc phn ng hu c

Cc phn ng hu c c phn loi theo nhiu cch khc nhau: Theo c im ca s bini lin kt, theo c im ca tc nhn phn ng, theo s lng cc tiu phn tham gia vo giaion quyt nh tc phn ng, theo hng ca phn ng hoc phi hp tt c cc cch phnloi ni trn.

a. Phn loi theo c im ca s bin i lin ktCc phn ng hu c thng thng xy ra bng cch lm t lin kt cng ho tr c v to

thnh lin kt cng ho tr mi. Mt lin kt cng ho tr c th b t theo hai cch khc nhau.

Theo cch th nht, sau khi lin kt cng ho tr b t mi nguyn t em theo n mtelectron ca i electron lin kt. Khi trong mi trng phn ng xut hin nhng gc t dohay nguyn t hot ng.

R : X R. + X.

Hay R X R. + X.

Cch t nh vy c gi l t i xng hay ng li v phn ng tng ng c gi lphn ng ng li hay phn ng gc t do.

Theo cch th hai, sau khi lin kt cng ho tr b t th i electron lin kt li mt

nguyn t, cn nguyn t kia khng em theo electron lin kt no.

R : X R + X

R X R + XHay

chnh l cch t khng i xng hay d li v phn ng xy ra trong trng hp ny lphn ng d li hay phn ng ion.

b. Phn loi theo c im ca tc nhn phn ngNhng tc nhn phn ng (Y-) l cc anion, cc phn t trung ho trong c nguyn t cn

cp electron t do c th cho i mt cch d dng, mt s phn t c cha electron c i lcmnh i vi trung tm mang in tch dng.

cr y ; y



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Nhng tc nhn nh vy c gi l cc tc nhn nucleophin (tc nhn i nhn). Phn ngxy ra vi s tham gia ca cc tc nhn nucleophin gi l phn ng nucleophin.

Cc tc nhn l nhng ion dng, nhng phn t c cha nguyn t khng c bt t y (axit liuyt), cc lng cc hoc phn t b phn cc di nh hng ca mi trng phn ngthng c i lc i vi trung tm mang in tch m.

cx z ; z

l cc tc nhn electrophin (tc nhn i in t). Phn ng xy ra vi s tham gia ca tcnhn electrphin c gi l phn ng electrophin.

c. Phn loi theo hng ca phn ngTheo cch ny ngi ta chia cc phn ng hu c thnh phn ng th, phn ng cng hp v

phn ng tch.

Phn ng th (k hiu l S) l phn ng trong mt nguyn t hay mt nhm nguyn ttrong phn t ny c thay th bng mt nguyn t hay mt nhm nguyn t khc. Th d, phn ng:

asktCH4 + Cl2 CH3Cl + HCl

y mt nguyn t hiro trong phn t metan c thay th bng nguyn t clo.

Phn ng cng hp (k hiu l A) l phn ng trong hai hay nhiu phn t kt hp vinhau to thnh phn t mi. Th d, phn ng cng hp phn t hiro vo phn t etylen tothnh etan.

NiH2C = CH2 + H2 CH3-CH3

Phn ng tch (k hiu l E) l phn ng trong mt phn t b loi i mt s nguyn thoc nhm nguyn t to thnh hp cht mi c ni kp. Th d, phn ng loi nc ca ancoletylic to thnh etylen.

H2SO4CH3-CH2-OH CH2=CH2 + H2O

Trong cc loi phn ng ni trn, ty thuc vo c im ca tc nhn phn ng chng cnc th c phn chia chi tit v c th hn. Chng hn, phn ng th c th gm phn ng thgc (SR), phn ng th electrophin (SE), phn ng th nucleophin (SN).



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Cn ch thm rng, trong qu trnh phn ng ca c ba loi phn ng trn u c th xyra s i ch mt nguyn t hay mt nhm nguyn t trong phn t c gi l s chuyn v.S chuyn v cng c th c coi l loi phn ng th t.

d. Phn loi theo s lng tiu phn tham gia vo giai on quyt nh vn tc ca phnng

Theo cch phn loi ny ta phn bit thnh phn ng n phn t, phn ng lng phn t,phn ng tam phn t v phn ng a phn t.

4. C ch phn ng

C ch phn ng l con ng chi tit m phn ng din ra t cht u n cht cui quacc hp cht trung gian v trng thi chuyn tip.

Hp cht trung gian (hay sn phm trung gian) l cc gc t do hay cc ion ng vi cc cctiu nng lng, cn trng thi chuyn tip (hay phc hot ng) l trng thi c nng l ng cci ca h phn t trc khi phn ng.

Th d:HO- + CH3B r HO

- ... CH3 ... Br- HO- CH3 + Br

-

Cht u trng thi chuyn tip cht cui

E

HCht u

Cht cui

TTCT


E2

E1HCTG

TTCT1TTCT2

E

HCht u

Cht cui

E

Tin trnh phn ng Tin trnh phn ng

E l nng lng hot ha, H l hiu ng nhit ca phn ng trong iu kin ng p. Phnng xy ra khi H< 0.

5. Cu trc phn t hp cht hu c

Trong ho hc hu c ta thng gp nhiu hp cht khc nhau v tnh cht, song li c cngmt cng thc phn t. Hin tng mt cng thc phn t ng vi hai hoc nhiu hp cht khcnhau c gi l hin tng ng phn. Hin tng ng phn c gii thch trn c sthuyt cu to ho hc ca nh bc hc Nga A. M. Butlrp. Do c hin tng ng phn m slng cc cc hp cht hu c c tm thy tng ln gp bi. C hin tng ng phn l do cccht c cu trc khc nhau.


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Ngi ta bit rt nhiu loi ng phn khc nhau, nhng chung quy li da vo cc cim v cu trc ta c th phn chng thnh hai loi chnh, l ng phn cu to (ng phnmt phng) v ng phn khng gian (ng phn lp th).

5.1. ng phn cu toCc ng phn cu to phn bit nhau v trt t sp xp ca cc nguyn t trong phn t

hoc v loi lin kt gia cc nguyn t, tc l phn bit nhau v mt cu to. Sau y l mt sng phn cu to ch yu.

a. ng phn mch cacbonCc ng phn loi ny phn bit nhau v cch sp xp cc nguyn t cacbon trong mch.

Th d, n-pentan; isopentan v neopentan u c cng thc phn t l C5H12, nhng c cu tomch cacbon khc nhau:

CH3 CH3CH3-CH2-CH2-CH2-CH3 CH3-CH-CH2-CH3 CH3-C-CH3

CH3n-pentan isopentan neopentan

S ng phn mch cacbon tng ln rt nhanh theo s nguyn t cacbon c trong phn t.Th d, butan C4H10 c 2 ng phn, heptan C7H16 c 9 ng phn, ecan C10H22 c 159 ngphn, triecan C13H28 c803 ng phn, tricontan C30H62 c 411846763 ng phn ...

b. ng phn nhm nh chcCc ng phn nhm nh chc c cng thnh phn phn t, nhng khc nhau v nhm nh

chc.

Th d: CH3-CH2-C-H v CH3-C-CH3O O

anehit propionic axeton

Hai cht ny cng c thnh phn phn t C3H6O, nhng c nhm nh chc khc nhau.Nhm nh chc ca anehit propionic l -CH=O, cn ca axeton l >C=O. Anehit propionic cim si 500C, tham gia c phn ng trng bc v phn ng vi thuc th Phlinh. Axeton si 400C, khng tham gia c phn ng trng bc cng nh phn ng vi thuc th Phlinh.

c. ng phn v tr nhm nh chcCc ng phn loi ny c cng thnh phn phn t, cng nhm nh chc, nh ng phn bit

nhau v v tr ca nhm nh chc trong mch cacbon.

Th d:

CH3-CH2-CH2-OH CH3-CH-CH3OH



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propan-1-ol propan-2-ol

Hai ng phn ny c cng thnh phn phn t C3H8O, cng nhm nh chc ru (nhm -OH), nhng v tr ca nhm -OH trong mch cacbon khc nhau.

d. ng phn lin ktCc ng phn ny phn bit nhau v loi lin kt gia cc nguyn t cacbon. Th d , buten-2

v xiclbutan.

H2C CH2

CH3-CH=CH-CH3 H2C CH2

But-2-en xiclobutan

Trong phn t hai ng phn ny cc nguyn t cacbon lin kt vi nhau theo cc cch khcnhau.

Ngoi bn loi ng phn cu to chnh trn y, hin tng h bin hay hin tngtautome l hin tng t chuyn ho qua li gia hai dng ng phn khng bn cng c xpvo mt loi ca ng phn cu to.

Th d, hai dng cu to tn ti trong dung dch ca axetamit:CH3-C-NH2 CH3-C=NH

O OH(dng amit) (dng imit)

5.2. ng phn khng gian

Cc ng phn khng gian c cng thnh phn phn t, cng mt cu to, nhng khc nhauv s phn b khng gian ca cc nguyn t hoc cc nhm nguyn t trong phn t. Hai loing phn khng gian chnh l ng phn hnh hc v ng phn quang hc. hai loi ny cccht ng phn phn bit nhau v cu hnh, tc l s phn bit trong khng gian ca cc nguynt hay cc nhm nguyn t xung quanh phn cng nhc hoc phn khng trng vi nh caphn t. Ngoi ra, cc ng phn cu dng cng c th c coi l loi ng phn khng gian thba. Tt c cc loi ng phn khng gian ny nhiu khi xut hin xen k nhau.

a. ng phn hnh hcNu c hai nguyn t ni vi nhau bng mt lin kt cng ho tr cng nhc, ngha l

khng c s quay ca hai phn phn t quanh trc ni ca hai nguyn t ny th hai nhm th nivi chng c th c nhng cch phn b khng gian khc nhau: Nu chng cng pha i vinhau ta gi l ng phn cis, khc pha l ng phn trans.

Da trn c s , ng phn hnh hc thng c cc hp cht c ni i cacbon-cacbon,ni i gia cacbon v mt s d t no hoc gia cc d t vi nhau v cc hp cht mchvng. l nhng phn cng nhc, lm cho cc nhm th ni vi chng khng c kh nng quayt do. Sau y l mt s th d:



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c C

h

cooh

h

hooc

c C

h

coohh

hooc

axit maleic (cis) axit fumaric (trans)

c C

h

ch3

h

hooc

c C

h

ch3h

hooc

axit iso crotonic (cis) axit crotonic (trans)

N N

C6H5C6H5

N NC6H5

C6H5r2

ho

n

C

r1 r2

n

C

r1

oh oxim azobenzen

ch3 ch3ch3

ch3 cis-1,2-imetylxiclopropan trans-1,2-imetyl xiclopropan

Cc ng phn hnh hc khc nhau r rt v tnh cht vt l v ho hc.

phn bit cc ng phn dng cis v dng trans ngi ta c th cn c vo:

- Mmen lng cc: mmen lng cc ca ng phn dng cis lun lun ln hn mmenlng cc ca dng trans.

Th d, phn t 1,2-icloeten:

CH Cl

CCl H

CH Cl

CClH

trans-1,2-icloeten cis-1,2-icloeten = 0 = 1,89D



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- Nhit si, nhit nng chy, t khi khc nhau. Chng hn, cis-1,2-icloeten si 60,80C, t trng l 1,283, cn trans- 1,2-icloeten si 47,90C v t trng l 1,256.

- Kh nng tham gia phn ng ho hc ca ng phn dng cis thng mnh hn ngphn dng trans.

Th d, axit maleic (dng cis) d dng tham gia phn ng loi nc to thnh anhiritmaleic.

CH

C

CH

OH=

OC

=O

OHC

HC

CH

O=

OC

=O

+ H2O

trong khi dng trans (axit fumaric) khng th tham gia phn ng ny.

b. ng phn quang hciu kin cn v xut hin ng phn quang hc cc hp cht hu c l phn t ca

chng phi c cc trung tm bt i xng. Trung tm bt i xng ph bin nht i vi cc hpcht hu c l nguyn t cacbon bt i, tc l nguyn t cacbon m bn ho tr ca n c linkt vi bn nguyn t hoc nhm nguyn t hon ton khc nhau.

Th d:Trong phn t axit lactic:

CH3

OH

HC COOH

Nguyn t C2 c lin kt vi cc nguyn t v nhm nguyn t -H, -OH, -CH3, -COOHhon ton khc nhau, do vy C2 l nguyn t cacbon bt i.

Ngi ta k hiu nguyn t cacbon bt i l C*.

Nhng phn t hp cht hu c c cha nguyn t cacbon bt i c th tn ti nhng cuhnh khng gian khc nhau v biu din chng ngi ta c th dng cc kiu m hnh hoc cngthc khc nhau, ph bin nht l cc m hnh t din, m hnh qu cu v c bit l cng thc chiuFis (Fisher)..

Phn t axit lactic trn y c hai cu hnh khng gian i xng nhau qua mt phng gng.



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CC

cooh

ho

ch3

h

cooh

h

ch3

oh

(b)

cooh

h

ch3

ho

cooh

ch3

ohh

(a)

(c)

cooh cooh

ch3

ch3

ho ohh h

ho

Cu hnh khng gian ca axit lactic

a) M hnh t dinb) M hnh khi cu v thanh nic) Cng thc chiu Fis

Hai cu hnh ny trng chng rt ging nhau, song khng bao gi c th trng kht ln nhauc, m chng lun lun i xng nhau nh vt v nh trong gng, nh bn tay tri v bn tay

phi, nh

hai chic giy ca mt iKhi trng thi lng, kh hoc trong dung dch chng uc kh nng lm quay mt phng nh sng phn cc. Gc quay i vi c hai dng u bng nhauv gi tr tuyt i, nhng hng quay th i lp nhau. Ngi ta gi l nhng ng phnquang hc.

Vy, ng phn quang hc l nhng cht c cng thnh phn phn t, c cng cu to, nhngc cu hnh khng gian khc nhau do c kh nng lm quay mt phng nh sng phn cc khcnhau.



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Ngoi nguyn t cacbon, cn mt s nguyn t khc nh nit, photpho, silic cng c thng vai tr trung tm bt i xng. Chng hn, ngi ta phn lp c cc mui amoni, cchp cht silic v cc photphin quang hot ca cc hp cht sau y:

(ch3)2ch

(ch3)2chch2 n ch2ch3.cl

ch3

;

c6h5

sihch3 p

n-c3h7

ch3c6h5;

Tnh quang hot cn c tm thy c mt s trng hp phn t khng trng vi nh mkhng c cc trung tm bt i xng.

Th d: axit 6,6- initro iphenic

NO2

NO2

COOH

COOH

NO2

NO2

COOH

COOH

Hai ng phn quang hc c tr s tuyt i ca gc quay cc bng nhau nh ng khc duc gi l hai cht nghch quang v chng to thnh mt cp nghch quang.

Trong t nhin v trong cc phn ng tng hp nhiu khi ngi ta nhn c cc ng phni quang cng vi nhau. Mt tp hp gm cc lng bng nhau ca cc ng phn quay phi vng phn quay tri gi l bin th raxemic. trng thi rn ta cn phn bit hn hp raxemic vhp cht raxemic. Hn hp raxemic l mt hn hp vi lng bng nhau cc tinh th ca dngquay phi v dng quay tri, khi hnh thnh tinh th t mt dung dch bin th raxemic th ccdng ny kt tinh ring r. Tri li, khi hnh thnh hp cht raxemic th cc phn t nghch quangkt hp tng i mt thnh t bo c bn ca tinh th, trong t bo ny lun c mt lng bngnhau ca cc ng phn quay phi v quay tri.

Trong trng hp phn t c nhiu trung tm bt i xng th s ng phn quang hc tngln rt nhanh. Chng hn, vi phn t c n nguyn t cacbon bt i khc nhau th s ng phnquang hc l 2n, s cp nghch quang v s bin th raxemic s l 2n-1. Tuy nhin, nu c nhngtrung tm bt i xng ging nhau trong phn t th s ng phn quang hc, cng nh s cpnghch quang v s bin th raxemic s t hn so vi cch tnh trn.

Th d,phn t , -ihiroxibutyric.

ch3-choh-choh-cooh* *



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Trong phn t ca n c hai nguyn t cacbon bt i, do vy s c 4 ng phn quang hc,to thnh hai cp nghch quang v hai bin th raxemic. Cng thc chiu Fis ca cc ng phnquang hc nh sau:

cooh

ch3

oh

oh

h

h

cooh

ch3

ho

h

h

hocooh

ch3

h

hho

ohcooh

ch3

h

h

ho

oh

Cn c vo cu hnh, cc cht hot quang c th c chia thnh hai dy ln: Dy D v dyL. l nhng k hiu dng ch cu hnh ca phn t cht hot quang. Cn c xp mt chthot quang no vo dy D hay dy L l cc cu hnh chun ca phn t glixeranehit. Phn tglixeranehit c mt C*, do c hai cu hnh khng gian khc nhau, ng vi hai ng phn

quang hc.

cho

ch2-OH

ohh ho

cho

ch2-OH

h

D(+)glixeranehit L(-)glixeranehit

Nhng cht hot quang c 1 C*, nu s sp xp H v OH quanh nguyn t C* ging s sp xpca D-glixeranehit th cht thuc dy D, nu s sp xp ging L-glixeranehit th thuc dy L.

Th d:

cooh

ch3

ohh ho

cooh

ch3

h

axit d(-)lactic axit l(+)lactic

i vi nhng cht c nhiu nguyn t C* ng

i ta cng xp t

ng t, nh

ng phi cn cvo cu hnh ca nguyn t C* xa nhm chc, trong nguyn t cacbon c ch s oxi ho caonht.



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Th d:

cho

ho

oh

h

ch2oh

oh

oh

h

h

h

choho

ohh

ch2oh

h

h

hho

ho

D(+) glucoz L(-) glucoz

Du (+), (-) trong cc cng thc chiu l dng ch chiu quay ca mt phng nh sngphn cc.

Trong cc hp cht khc, nhm chun c th l SH, NH2, X, CH3.

Hin tng quang hot rt ph bin trong cc hp cht hu c, c bit trong cc hp cht tnhin v c ngha sinh hc rt ln. Trong t nhin, c nhiu cht (gluxit, axit amin, protein,ankaloit) l nhng cht quang hot.

c. Cu dngKhi nim cc cu dng hay cn gi l cc hnh th ca mt phn t dng ch cc dng

cu trc khng gian ca n ch phn bit nhau do quay quanh mt lin kt n v khng th av trng kht ln nhau. Chng hn, phn t etan, hai nhm metyl c th quay quanh trc lin kt

cacbon-cacbon v do phn t c th c v s cu dng khc nhau, trong hai cu dng inhnh l cu dng che khut v cu dng xen k. biu din cc cu dng ng i ta dng cngthc phi cnh hoc thun tin hn l cng thc Niumen.

Cu dng che khut: Cu dng xen k:

h

h

h

h

hh

h

hh

h

hh

h

h

h

h

h

hhh

h

h

hh

cng thc phi cnh cng thc Niumen cng thc phi cnh cng thc Niumen

cu dng che khut, cc nguyn t hiro ca hai nhm metyl che khut nhau. cu dngxen k, cc nguyn t hiro ca hai nhm metyl vo ch trng ca nhau. Cu dng xen k bnhn cu dng che khut, hiu s nng lng gia hai dng ny l 2,8 kcal/mol.



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cc dn xut th 1,2 ca etan ta cng xt tng t. Tuy nhin, s cu dng in hnh ykhng phi l hai, m l su, trong c ba l dng xen k v ba l dng che khut. Th d, n-butan ta c ba cu dng xen k v ba cu dng che khut nh sau:

h

hch3

ch3

h

h h

h

ch3ch3

hh

h

h

ch3ch3

hh h

hch3ch3

hh

hh

ch3

ch3

hh h

hch3

ch3

hh

dng i (anti) cc dng lch dng khut cc dng na khut

Cc dng lch v na khut mc nng lng nh nhau. Cu dng u tin l cu dng i.Cu dng ny bn hn cu dng lch 0,8 kcal/mol, bn hn cu dng na khut 3,4 kcal/mol vcu dng khut khong 4,4 - 6,1 kcal/mol.

Ta gi cc cu dng c th tn ti bn vng l cc ng phn cu dng.

Cc ng phn cu dng thc t c tn ti v c th nhn bit c thng qua vic kho stcc tnh cht vt l v ho hc, song khng th phn lp c chng ring bit bi v chng rt ddng chuyn ho ln nhau qua vic quay quanh trc lin kt n.

6. nh hng tng h gia cc nguyn t v nhm nguyn ttrong phn t hp cht hu c

Vn nh hng tng h gia cc nguyn t v nhm nguyn t trong phn t hp chthu c c nh bc hc Nga A. M. Butlrp trnh by trong thuyt cu to ho hc nm

1861. Sau , Maccpnhicp pht trin thnh hc thuyt gi l thuyt nh hng tng hgia cc nguyn t v nhm nguyn t trong phn t hp cht hu c. Ni dung ca hc thuytny c trnh by di dng mt s hiu ng in t sau y.

6.1. Hiu ng cm ng

hiu th no l hiu ng cm ng, trc ht chng ta xt mt s th d sau y.

Th d 1,so snh mc linh ng ca nguyn t hiro trong nhm hiroxyl ca axit axeticv axit cloaxetic.

CH3-C-O-H Cl-CH2-C-O-HO O

axit axetic axit cloaxetic

Ka= 1,8. 10-5 Ka= 155. 10-5

c hai axit trn u c nhm cacboxyl (-COOH). Trong nhm ny lin kt O-H vn llin kt phn cc v pha nguyn t oxi do n c m in ln hn. Mt khc, nhm cacbonyl(>C=O) cng ht electron dng chung trong lin kt C-O v pha mnh, khin cho nguyn t oxi



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cng ht cp electron dng chung ca lin kt O-H v pha n mnh hn. Kt qu l lin kt O-Hcng phn cc mnh v nguyn t H trong nhm -OH tr nn linh ng. Ta c th biu din qutrnh nh sau:

c oh

o

Qua hng s Ka ta thy tnh axit ca axit cloaxetic mnh hn rt nhiu so vi axit axetic.Ni mt cch khc, nguyn t H trong nhm OH ca axit cloaxetic linh ng hn ca axit axetic.Nguyn nhn ca iu c gii thch nh sau: Trong phn t axit cloaxetic, nhm cacboxylc lin kt trc tip vi nhm -CH2Cl, do nh hng ca nguyn t clo c m in ln mlin kt C-Cl b phn cc v pha nguyn t clo. Nh s phn cc ny m nguyn t clo mangphn in tch m (k hiu -), nguyn t cacbon trong nhm CH2 mang phn in tch dng (khiu +), nguyn t cacbon ny li ht cp electron dng chung gia n v nguyn t cacbontrong nhm cacboxyl v pha n, t gy nh hng tip theo v cui cng dn n lin kt O-H

tr nn rt phn cc.

c o h

o

cl ch2+ +

Ngc li, trong phn t axit axetic, nhm cacboxyl lin kt vi nhm metyl (-CH3). Ngita chng minh c rng nhm metyl c kh nng y li cp electron ra xa mnh. Trongtrng hp nhm metyl trung ho bt phn in tch dng ca nguyn t cacbon trong nhmcacboxyl, t gy nh hng tip theo lm gim bt s phn cc ca lin kt O-H.

c o h

o

ch3+

nh hng ca nguyn t clo v nhm metyl theo kiu nh vy c gi l hiu ng cmng. Nguyn t clo v nhm metyl l nhng trung tm gy nn hiu ng cm ng.

Th d 2, xt hai phn t propan v n-propyl clorua ta thy rng, khc vi propan, phn t n-propyl clorua c lin kt C1-Cl b phn cc mnh v pha nguyn t clo l nguyn t c min ln hn.

c c c

h h h

hhh

h h c c c

h h h

hhh

h cl+" +' +

3 2 1

Do nguyn t clo mang mt phn in tch m, cn nguyn t C1 mang mt phn intch dng. V nguyn t C1 mang mt phn in tch dng nn lin kt C1-C2 cng b phn ccv pha C1, ri n lin kt C2-C3 cng b phn cc v pha C2, mc d s phn cc yu hn



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nhiu. S phn cc cng xy ra c cc lin kt C-H trong phn t. Kt qu chung l phn tn-propyl clorua l phn t phn cc.

T nhng th d trn ta c th hiu v hiu ng cm ng nh sau: Hiu ng cm ng l s dichuyn my electron dc theo mch cacbon di tc dng ht hoc y ca cc nguyn t th haynhm th; hay hiu ng cm ng l s phn cc lan truyn cc lin kt lin tip theo mch linkt do s phn cc ca mt lin kt no .

Ngi ta thng dng mi tn thng ( ) ch hng lan truyn ca hiu ng cm ng.

Hiu ng cm ng c k hiu bng ch I (Inductive effect). Nu quy c rng trong linkt (C-H), nguyn t H c I=0 th nhng nhm th c kh nng ht electron mnh hn H ccoi l nhng nhm c hiu ng cm ng m (-I), cn nhng nhm c kh nng y electron mnhhn H l nhng nhm c hiu ng cm ng dng (+I).

y c+i

+ h c x c

+

-ii=0

Hiu ng +I thng thy cc nhm ankyl v cc nhm mang in tch m. Nhm ankylcng ln, cng phn nhnh hiu ng +I cng ln. Trong cc nhm mang in tch m, m incng nh hiu ng +I cng ln.

-ch3 < -ch2-ch3 < -chch3

ch3

< -cch3

ch3

ch3

-o < -s < -se Hiu ng -I thng thy cc nhm khng no, cc nhm mang in tch dng v cc

nhm ng vi nhng nguyn t c m in ln. Ni chung, cc nhm cng khng no, c m in cng ln th hiu ng -I cng ln.

-c cr > -cr=cr 2 > -cr2-cr3

-or2 > -or ; -NR3 > -NR2

-f > -cl > -Br > -I

-or2 > -sr2 > SeR2 , ... c tnh quan trng nht ca hiu ng cm ng l n gim rt nhanh khi mch cc lin kt ko di. Th d, phn t axit butyric:

ch3 - ch2 - ch2 - c - o - ho

=



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Nu thay th mt nguyn t H cc v tr, , bng nguyn t clo th lm cho lc axittng ln. Nu nguyn t clo v tr lc axit tng 92 ln, nu v tr lc axit tng 6 ln, cnnu v tr lc axit ch tng c 2 ln so vi lc axit ca axit butyric.

6.2. Hiu ng lin hpHiu ng lin hp ch c trng cho cc phn t c cha h lin hp.

Phn t c cha h lin hp l nhng phn t t.rong c cc lin kt bi lun phin linkt n -) hoc nhng phn t trong cn nguyn t hay nhm nguyn t c cp electronkhng phn chia (cp electron t do, cha tham gia lin kt) cch lin kt bng mt lin ktn.

Th d: Cc phn t sau y c cha h lin hp:

ch2 = ch - ch = ch2 ; ch2 = ch - ch = ch - ch =Och3 - c - nh2 ; ch2 = ch -cl

o

;oh

=

cc h lin hp nh vy c mt c ch chuyn dch electron c trng cho obitan phn tca h lin hp, khc hn c ch chuyn dch cm ng trn. biu din chiu chuyn dchin t trong h lin hp ngi ta dng mi tn cong.

Th d: Phn t lin hp but-1,3-ien trng thi bnh thng khng phn cc, 4 electron pca 4 nguyn t cacbon xen ph ln nhau, pha ho chung vo nhau to thnh mt obitanphn t duy nht gii ta u trn c 4 nguyn t cacbon.

CH2 CH CH CH2

+

-

CH2 CH CH CH2

Nu thay th mt nguyn t H nhm -CH2 bng nhm -CHO chng hn th nhm ny s thamgia lin hp vi obitan phn t ca butaien. Nh c tnh phn cc sn c ca nhm -CHO, tonb obitan phn t mi hnh thnh ca phn t b dch chuyn mt phn v pha nguyn t xi.Ta ni y c hiu ng lin hp -.



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CH2 CH CH CH CH O

++

-

CH2 CH CH CH CH O

Mt th d khc, trong phn t vinyl clorua:

ch2 = ch - cl

Nguyn t clo cn ba cp electron p t do cha tham gia lin kt. Mt trong ba cp ny ctrc song song vi trc ca cc electron ti vng ni i, v vy chng s tham gia lin hp vinhau to thnh obitan phn t mi. Ton b obitan phn t mi ny b y lch v pha nguynt C2.

ch2 = ch cl

Hiu ng lin hp trong trng hp ny l hiu ng lin hp p-.

Vy, hiu ng lin hp l hiu ng dch chuyn my electron trong h lin hp di nh

h

ng ht hoc y electron ca cc nhm th.Hiu ng lin hp c k hiu bng ch C (conjugate effect). Ngi ta cng phn bit hiu

ng lin hp thnh hai loi: Hiu ng lin hp m (-C) v hiu ng lin hp dng (+C).

Nhng nhm th c kh nng ht electron gy ra hiu ng lin hp m, thng l nhngnhm th khng no nh cc nhm -NO2, -CN, -CHO, -COOH, >C=O, >C=NH ...Hng chuyndch electron trong h lin hp c cha nhm vi hiu ng -C c m t nh sau:

c c c y

Dy nhm th sau y gy ra hiu ng -C gim dn:

o-no2 > -cho > -c-r > -c-oh

o= =

Cc nhm th c kh nng y electron gy ra hiu ng lin hp dng, l cc nhm thc cp electron p t do nh cc halgen (-X), -NH2, -OCH3, ...Hng chuyn dch electron theohng i v pha lin kt .



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c cx

Dy nhm th sau y gy ra hiu ng +C gim dn:

- F > - Cl > - Br > -I > -OH > - NH2

Ngoi nhng nhm th lun lun biu hin hiu ng -C hoc +C, cn c mt s nhm chiu ng lin hp vi chiu thay i tu thuc vo bn cht ca nhm th lin kt vi chng. l cc nhm nhvinyl (CH2=CH-), phenyl (C6H5-), etinyl (CH C-) ...

Th d:

+c -c -c +C

n

o

onh2

Mt s nhm th nh cc halogen, -NH2, -OH, vvng thi gy hai hiu ng +C v -Ingc chiu nhau. Trong nhng trng hp nhvy, ni chung +C > -I v hiu ng +C quyt nhc kh nng ln chiu hng phn ng. Ring trng hp cc halogen, do c m in lnnn -I > +C, hiu ng -I quyt nh kh nng phn ng, nhng hiu ng +C quyt nh chiuhng ca phn ng.

Xt v c tnh ca hiu ng lin hp ngi ta thy rng khc vi hiu ng cm ng, hiu

ng lin hp ch thay i rt t nu tng chiu di mch lin hp. c tnh na l hiu ng linhp ch xut hin trn h lin hp phng hay gn phng, tc l h lin hp trong trc ca ccocbitan v p song song hay gn nh song song vi nhau.

H phng

xen ph

H khngphng

khng xen ph

6.3. Hiu ng siu lin hp

Trong h thng nhng phn t c cha nhng lin kt C-H ng cch lin kt kp bi linkt n C-C nh:



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- C - C = C ;

H

- C - C N ;

H

- C - C = O

H

nhng h thng nh vy c s lin hp gia cp electron ca lin kt kp vi cpelectron ca lin kt C-H (dng mi tn cong i t lin kt C-H n lin kt C- C ch s linhp ). S lin hp nhvy c gi l hiu ng siu lin hp hay hiu ng lin hp -.

cC

H

c cC

H

N cC

H

O; ;

Hiu ng siu lin hp c k hiu bng ch H (hyperconjugate effect). Hiu ng siu linhp tng theo s lng lin kt C-H v tr ca nhm ankyl.

- CH3 > - CH2- CH3 > -CH(CH3)2 > - C(CH3)3

Trn y chng ta cp n ba loi hiu ng chnh thng c biu hin trong cc hpcht hu c. Vic xem xt cc hiu ng ny cho php ta tin on c kh nng phn ng vnhng chiu hng chnh s xy ra ca cc phn ng hu c, ng thi cn cho php gii thchcnhiu tnh cht ca cc hp cht hu c. V vy hiu c chng l rt cn thit nghincu v cc hp cht hu c v cc phn ng hu c.



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Cu hi v bi tp

1. Cc loi ng phn? Biu din cc ng phn bng cng thc cu to hoc cu hnhkhng gian thch hp.

2. Cc loi hiu ng in t trong phn t hp cht hu c. ng dng ca vic xt cc hiung in t trong ho hc hu c.3. Vit cng thc cu to cc ng phn c th c ca cc hp cht c cng thc phn t

C6H12; C4H8; C2H4O2; C3H6O.4. Cu hnh khng gian v gi tn cc ng phn hnh hc ca cc hp cht sau:

But-2-en2-metylbut-2-enoic1,2- iclo xiclopropanBut-2-enioic

5. Cng thc chiu Fis v gi tn cc ng phn quang hc ca cc hp cht sau:Axit lactic

AlaninAnehit glixericSerinGlucozFructoz

6. So snh tnh linh ng ca nguyn t H trong nhm -OH ca cc hp cht sau v giithch bng cc hiu ng in t:

HOH; C2H5OH; HCOOH

7. So snh tnh axit ca cc axit sau v gii thch:

HCOOH; CH3- CH2- COOH; CH3- CH2-CH2- COOH v CH3- CH- COOHCH3

CH3- CH2- CH2- COOH; CH2= CH- CH2- COOH v CH3- CH= CH- COOHCH3- CH2- COOH; CH3- CH- COOH v CH2- CH2 - COOH

Cl Cl

8. So snh s phn cc ca lin kt C- Cl gia cc hp cht sau v gii thch.

CH3CH3- CH2- CH2- Cl; CH3- CH- Cl v CH3- C- Cl

CH3 CH3CH3- CH2- Cl v C6H5- Cl

9. Xt chiu phn cc ca cc lin kt trong cc hp cht sau y v gii thch.Pent- 2-en2- metylbut-2-enVinyl cloruaAllyl clorua



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Chng II

Hirocacbon

Hirocacbon l hp cht hu c trong phn t ch gm cc nguyn t cacbon v hiro. Ccnguyn t cacbon lin kt vi nhau thnh mch cacbon.

Tu theo cu to mch cacbon ngi ta chia hirocacbon thnh: Hirocacbon dy khngvng (hirocacbon axiclic) v hirocacbon dy vng (hirocacbon xiclic).

Trong mi dy, tu thuc bn cht ca lin kt gia cacbon v cacbon c th chiahirocacbon thnh ankan, anken, ankaien, ankin, xiclo anken, xiclo anken, hirocacbon thm.

Trong chng ny chng ta ch cp n mt s hirocacbon chnh, l hirocacbon no,hirocacbon khng vng cha no v hirocacbon thm.

1. Hirocacbon no (ankan, xicloankan)

Hirocacbon no bao gm ankan v xicloankan.

Trong phn t hirocacbon no, cc nguyn t cacbon lin kt trc tip vi nhau bng linkt xch ma ().

An kan l hirocacbon mch khng vng c cng thc chung l CnH2n+2 ( n 1).

Xicloankan l hirocacbon mch vng c cng thc chung l CnH2n ( n 3).

1.1. Cch gi tn v ng phn

a. Tn gi thng thng

Cc ankan c tn cng l ui an (ngha l no). Bn cht u ca dy ng ng c tngi khng h thng:

CH4 C2H6 C3H8 C4H8metan etan propan butan

Nhng ankan tip theo gi tn theo th t:Ch s Hilp ch s nguyn t cacbon + an

Th d:

C5H12 C6H14 C7H16pentan hexan heptanC8H18 C9H20 C10H22octan nonan ecan


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ch hircacbon khng phn nhnh thng thm tip u ng n (normal) hoc khngc. Tip u ng iso gi nhng hp cht c hai nhm metyl u mch khng phn nhnh,cn tip u ng neo ch hp cht c 3 nhm metyl u mch khng phn nhnh.

Th d: CH3CH3- CH2 -CH2- CH2- CH3 CH3 - CH- CH2- CH3 CH3- C- CH3

CH3 CH3n-pentan isopentan neopentan

b. Tn gc v bc ca gc

Trong hp cht hu c thng gp nhng nhm nguyn t c xem nh mt n v cutrc c thnh phn, s lng tng t ankan, ch t hn mt nguyn t hiro c gi l gc ankyl(cng thc chung CnH2n+1-). Tn gc ankyl ging ankan tng ng ch thay ui an bng uiyl.

Th d:CH3- C2H5- C3H7-metyl etyl propyl

Da vo bc ca nguyn t cacbon mang ho tr t do, cc gc ankyl li c chia thnh:gc ankyl bc I, gc ankyl bc II, gc ankyl bc III.

Th d:CH3-CH2-CH2-CH2- CH3- CH2 - CH-

CH3n- butyl (gc bc I) sec- butyl (gc bc II)CH3 - CH - CH2- CH3

CH3 CH3- C-CH3iso- butyl (gc bc I) tert- butyl (gc bc III)

c. Tn gi IUPAC

Danh php h thng ho y nht l danh php IUPAC ca hip hi ho hc quc t vng dng (International Union of Pure and Applied Chemistry). Nguyn tc gi tn ankan theoIUPAC bao gm cc im sau:

- Tn ca ankan c kt thc bng an.-Mch chnh c chn l mch cacbon di nht khng phn nhnh. Nhng nhm

ankyl kt hp vi mch chnh c xem nhnhm th.-Vic nh s mch chnh c tin hnh t pha no sao cho tng cc ch s ca

nhm th l b nht. Mi nhm th c ch s tng ng vi v tr ca n trong mch.-Trng hp c cc nhm th ging nhau cng mt nguyn t cacbon hoc cc

nguyn t cacbon khc nhau th phi ghi s ch ca mi mt nhm th trong chng.-Gi tn theo th t:


V tr nhnh + tn nhnh + tn mch chnh

Khi c mt nhiu nhm th khc nhau th th t gi tn c th theo th t tng dn tnhphc tp ca nhm th hoc theo a, b, c.


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Th d:

CH3 - CH - CH - CH2 - CH2 - CH3 CH3CH3 CH3 CH3 -C - CH - CH2 - CH2 - CH3

CH3

CH2-CH

3

2,3 -imetyl hexan 2,2-imetyl-3-etyl-hexan

Cc xicloankan c gi tn theo cch gi IUPAC. Mch chnh lun phi l mch vng.Vic nh s ch c tin hnh i vi cc xicloankan c hai nhnh tr ln. Bt u nh s tnguyn t cacbon lin kt vi nhnh n gin nht v theo chiu sao cho tng s s ch v trmch nhnh l nh nht, sau gi tn theo th t:

V tr nhnh + tn nhnh + xiclo + tn ankan tng ng

Th d:

CH3

mtylxiclhexan

CH2 -CH3

CH3

1-mtyl-2-tylxiclpentan

d. ng phn

Cc ankan c ba loi ng phn chnh l ng phn mch cacbon, ng phn quang hc vng phn hnh th.

Th d 1: Cc ng phn v cu to mch cacbon ca pentan. CH3CH3- CH2 -CH2- CH2- CH3 CH3 -CH- CH2- CH3 CH3- C- CH3

CH3 CH3n- pentan isopentan neopentan

Th d 2: C7H16 c hai cng thc cu to cha nguyn t cacbon bt i, do c cc ngphn quang hc.

-CH -CH2 -CH3

CH3CH3 -CH

*

-CH -CH2 -CH2 -CH3CH3

CH3 -CH2*

CH3 Th d 3: ng phn cu dng ca n-butan

CH3

dng i ca butan

HCH3 CH3CH3

H

HHHH

HH

dng khut ca butan Xicloankan c s ng phn nhiu hn s ng phn ca ankan. Xicloankan c cc loi

ng phn sau:



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- ng phn v cu to mch cacbon phn nhnhTh d:

CH -CH3CH3

CH2 -CH2 -CH3

n propylxiclopentan isopropylxiclopentan - ng phn v cu to mch vngTh d:

CH3

metylxiclopentan xiclohexan - ng phn v v tr nhnhTh d:

CH3CH2 -CH3

CH3

CH2 -CH31-metyl-2-etyl xiclohexan 1-metyl-4-etyl xiclohexan

- ng phn hnh hcTh d:

CH3

CH3

CH3

CH3

cis -1,2-imetylxiclopropan

trans -1,2-imetylxiclopropan

1.2. Phng php iu ch

a. Phn ng Vuyc- FitticNguyn tc ca phng php ny l cho dn xut halgen tc dng vi kim loi Na.

CH2CH3 -

+ 2 NaCH2CH2 -CH2 -CH3

- CH -CH3

CH3

Cl - CH -CH3

+ 2NaBrt0

+ 2 Na +CH2-ClCH3 -

Br Br

t0 + 2NaCl

b. Phn ng cacboxyl ho

iu kin nhit cao v c xc tc, axit cacboxylic b loi CO2 to thnh ankan.



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Th d:

CH2CH2 -

+ CO2t0

CH3CH3 -xtCH2-COOHCH3 -

MnO2, t0 CH2CH2 -

- H2O,CH2-CCH2 -

O

OH

CH2-CCH2 -OOH [H]

Zn + HCl- H2O

CH2CH2 -

CH2CH2 -C =O CH2

-CO2

Thng thng ngi ta tin hnh cacboxyl ho mui cacboxylat.

Th d:

CH2CH2 -

t0

CH2CH2 -

CH2-CCH2 -

OO

CH2-CCH2 - OO[H]

Zn + HCl- H2O

CH2CH2 -

CH2CH2 -C =O CH2Ca -CaCO3

CH3COONa + NaOH rnCaO

t0

CH4 + Na2CO3

c. in phn dung dch mui natri ca axit monocacboxylic

p2 RCOONa + 2 H2O R -R + 2 NaOH + 2 CO2 + H2

1.3. Tnh cht vt l

Ankan l nhng cht khng mu, khng mi, t tan trong nc, tan nhiu trong dung mihu c, c khi lng ring nh hn 1,0.

Bn cht u ca dy ng ng l cht kh, nhng ankan c t 5-17 nguyn t cacbontrong phn t l cht lng, t C18H28 tr ln l nhng cht rn.

Nhit si, nhit nng chy tng dn theo chiu tng mch cacbon. Cc ng phnmch nhnh c nhit si thp hn ng phn mch thng. nhit si cng thp nu s nhnhcng nhiu v cng gn u mch chnh.

Xicloankan cng l nhng cht khng mu, khng mi c nhit si cao hn nhit sica ankan tng ng. Xiclopentan v xiclohexan l nhng cht lng, cn cc xicloankan cao hnl nhng cht rn.

1.4. Cu to

Trong phn t ankan v xiclankan cc nguyn t cacbon u trng thi lai ho sp 3. Bnobitan lai ho sp3 ca nguyn t cacbon c hnh dng, mc nng lng nh nhau hng v bnnh ca mt t din u. Gc ho tr l 109028. Bn obitan lai ho sp3ca nguyn t cacbon nyto vi obitan sp3 ca nguyn t cacbon khc hoc vi obitan s ca nguyn t hir bn lin kt



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. Do trong phn t ankan ch gm cc lin kt bn vng nn ankan kh tham gia cc phn ngho hc.

Hnh 2.1. Cc lin kttrong phn t metan v etan

Trong phn t xicloankan cng ch gm cc lin kt bn vng, nhng do mch cacbonng vng lm cho gc lin kt b thay i so vi gc ho tr 109 028, dn n bn ca cc

xicloankan thay i. Cc xicloankan c s cnh ca vng khc nhau, gc lin kt khc nhau, bns khc nhau.

gii thch bn khc nhau ca cc xicloankan, nm 1885 Annph Bayer a rathuyt sc cng Bayer. Ni dung ca thuyt sc cng Bayer nh sau:

- Mi nguyn t cacbon to vng cng nm trn mt mt phng, ngha l vng c cu tophng.

- Gc ho tr bn l gc 109028. Cc gc ho tr ca vng ln hn hay nh hn 109028 ulm cho lin kt cacbon-cacbon km bn v n phi chu mt lc cng ra hay p li.Gc cng hay gc p cng ln vng cng km bn v kh nng phn ng ca vng cngln.

Gc cng hay p c tnh bng biu thc:

109028' -2

=

Trong : l gc cng hay gc p

l gc ca vng

Kt qu tnh chnh lch gc ho tr ca mt s xicloankan nh sau:

n 3 4 5 6 7 8 +24044 +9044 +0044 -5016 -9033 -12051

Nh vy sc cng ln nht l xiclopropan, nhng sc cng ny gim bt mt cht do nhngobitan lai ho ca nguyn t cacbon b xen ph theo dng lin kt hnh qu chui.



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1600

600

Hnh 2.2. Lin kt hnh qu chui

Lin kt ny km hiu qu, l trung gian gia lin kt v lin kt . iu cho php giithch xiclopropan c khuynh hng tham gia phn ng cng hp m vng.

Khi tng kch thc ca vng chnh lch ca gc ho tr so vi gc l tng gim. Nhngxiclohexan c gc ca vng l 1200, vy n phi c sc cng ln hn xiclopentan. Kt lun nymu thun vi tnh cht. S d nh vy l v thuyt sc cng Bayer da vo gi thuyt cu to

phng ca mi h thng xicloankan. Thc t chng c s sp xp khng gian khng phng cacc nguyn t cacbon trong vng, do sc cng gim.

1.5. Tnh cht ho hc

iu kin thng cc ankan km hot ng ho hc, chng khng phn ng vi kim c,axit c v cc cht oxi ho nh kali pecmanganat, kali bicromat. nhit cao hoc trongnhng iu kin c bit ankan tham gia mt s phn ng, trong phn ng th, phn ng hul nhng phn ng quan trng nht.

a. Phn ng th

Quan trng hn c l phn ng halogen ho, l phn ng thay th nguyn t hiro caankan bng nguyn t halogen. Phn ng ch thc hin c khi c nh sng khuch tn hocnhit cao.

Phng trnh phn ng tng qut:

hRH + X2 RX + HX(t0)

thy r trung tm phn ng, ta c th biu din di dng sau:

h(t0)

C - H + X2 C -X + HX

y, X2 l F2, Cl2, Br2, I2.

Phn ng xy ra theo c ch th gc (SR)qua cc giai on:- Giai on u tin l giai on khi mo phn ng. Do tc dng ca nh sng t ngoi

hoc nhit cao, lin kt gia hai nguyn t halogen b ct t theo kiu ng li tothnh hai nguyn t halogen hot ng, mi nguyn t halogen mang mt in t t do:



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hX X 2X

- Giai on tip theo, nguyn t halogen hot ng tc dng vi ankan ct t ng li linkt C-H to ra mt gc cacb t do, gc ny phn ng tip vi phn t halogen khc to radn xut halogen v nguyn t halogen hot ng. Phn ng tip tc xy ra lp i lp litheo kiu phn ng dy chuyn. Giai on ny thng c gi l giai on pht trinmch.

C - H + X C + HX

C + X2 CX + X

- Phn ng dng li khi xy ra mt trong s cc phn ng sau:

X X X2

C C C C

C X C -X+

+

+

Giai on ny c gi l giai on tt mch.Kh nng tham gia phn ng halogen ho gim dn t flo n it. Flo phn ng cc k mnh

lit vi ankan cho sn phm ca phn ng hu do tt c cc lin kt C-C v C-H u b ct t.Cc ankan c cc nguyn t cacbon bc khc nhau trong phn t khi tham gia phn ng s cho

nhiu sn phm, nhng sn phm th nguyn t hiro ca nguyn t cacbon bc cao l sn phmchnh.

Th d:

h

CH3

CH3 -CH -CH3 + Cl2 CH3 -C -CH3 + CH3 -CH -CH2Cl + 2 HCl

CH3

Cl

sn phm chnh sn phm ph

CH3

22

b. Phn ng cng hp ca xicloankan

Cc vng 3, 4 cnh km bn, c tnh cht ging anken, chng d dng tham gia cc phnng cng hp m vng.

Th d:

CH2H2C

CH2

+ Br2 Br -CH2 -CH2 -CH2 -Br

c. Phn ng oxi ho


iu kin bnh thng cc ankan khng b oxi ho bi oxi khng kh, cc cht oxi homnh nh H2SO4 c, KMnO4Nhng nhit cao, cc ankan b oxi ho to thnh snphm cha oxi. Khi un nng t 100 - 1600C vi s c mt ca cc cht xc tc (KMnO4,Na2CO3) cc ankan b oxi ho bi oxi khng kh to thnh cc axit.


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Th d:

CH3 -(CH2)16 -CH3 + 3 O2 2CH3 -(CH2)16 -COOH + 2 H2O100 -1600C

Trong mt s trng hp c th gy nn s t mch cacbon.

CH3 -(CH2)n -CH3 CH3 -(CH2)x -COOHO2,xt

CH3 -(CH2)y -COOH

Khi c mt oxi d, cc ankan b chy to thnh kh CO2 v H2O, ng thi gii phng mtlng nhit ln.

Th d:

CH4 + 2 O2 CO2 + 2 H2O +885Kj

Chnh v th m mt s ankan c dng lm nhin liu t.

d. Phn ng hu

nhit cao, khng c oxi khng kh, cc ankan b phn hu gy mch to thnh cc ankanv cc hirocacbon khng no (anken) c mch ngn hn. Qu trnh ny c gi l qu trnhcrckinh.

CnH

crckinh

2n+2 CxH 2x+2 2yCyH+ ankan anken

2 CH3-CH2-CH2-CH3 CH3-CH=CH2 + CH4 + CH2=CH2 + CH3-CH3

Phn ng ny c dng nhiu trong cng nghip du m iu ch xng.

2. Hirocacbon khng vng cha no (anken, ankaien, ankin)

Hirocacbon cha no l nhng hirocacbon m trong phn t c mt hay nhiu lin kt pi(). Nhng hirocacbon thuc loi ny ch yu gm c: anken, ankaien, ankin.

Anken l hirocacbon cha no, mch h c mt lin kt i trong phn t. Cng thc chungl CnH2n (n2).

Cc anken lp thnh mt dy ng ng, ng u dy ng ng l tylen (C2H4).

Ankaien l hirocacbon cha no, mch h c hai lin kt i trong phn t. Cng thcchung l CnH2n -2 (n3). Tu theo v tr ca hai lin kt i ngi ta phn ankaien thnh ba loi:

- Ankaien c hai lin kt i cch xa nhauTrngi hc Nng nghip H Ni - - Gio trnh Ho hu c..4040


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Th d: CH2=CH - CH2 - CH2 - CH=CH2

hex-1,5-ien

-

Ankaien c hai lin kt i lin nhauTh d: CH2=C = CH2 CH3- CH = C = CH2

prop-1,2-ien but-1,2-ien

- Ankaien c hai lin kt i xen k mt lin kt n (ankaien lin hp)

Th d: CH2=CH - CH = CH2 CH2=C - CH = CH2CH3

but-1,3 -ien 2-metylbut-1,3-ien(iso pren)

- Ankin l hirocacbon cha no, mch h c mt lin kt ba trong phn t. Cng thcchung l CnH2n -2 (n2). Chng lp thnh mt dy ng ng, ng u dy ngng l axetylen (C2H2).


2.1. Cch gi tn v ng phn

a. Tn gi thng thng

Cch gi tn ny ch p dng cho cc hircacbon khng vng, cha no n gin, c mtlin kt i. Ngi ta gi tn ankan tng ng ri thay ui an bng ui ylen.

Th d:

CH2=CH2 CH3-CH=CH2 CH3-C=CH2CH3

etylen propylen isobutylen

Mt s ankaien c tn gi h thng nh sau:

CH2=C=CH2 CH2=CH-CH=CH2 CH2=CH-CH2-CH2-CH=CH2 CH2=C-CH=CH2CH3

allen ivinyl iallyl isopreni vi cc ankin, ngi ta ly axetilen lm cht gc, cn cc ng ng ca axetilen ccoi l dn xut th ca axetilen khi th nguyn t hir trong axetilen bng gc ankyl v gi tn nhsau:

Tn gc ankyl + axetilenTh d:

CH3-C CH CH3-C C-CH3metyl axetilen imetyl axetilen


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b. Tn gi IUPAC

gi tn cc hirocacbon khng vng cha no theo tn gi IUPAC, th t cc bc tngt nh gi tn ankan, nhng ch khc:

- Chn mch chnh l mch cacbon di nht cha lin kt kp.- nh s th t cacbon trn mch chnh bt u t pha gn lin kt kp nht.- Mch chnh c tn gi ca ankan tng ng b ui an, s ch v tr lin kt kp v ui

en, ien hoc in.

Th d:

CH3-CH=CH-CH3 CH2=C-CH=CH2 CH3 C C-CH-CH3CH3 CH3

but-2-en 2-metylbut-1,3-ien 4-metyl pent-2-in


Cc gc cha lin kt i c tn gi chung l ankenyl. Cn ch tn gi thng dng ca

mt s ankenyl sau y:CH2=CH- CH2=CH-CH2- CH2=C-

CH3vinyl allyl iso- propenyl

CH2= CH3-CH=metylen etylien

Gc ho tr mt ca ankin gi l ankinyl.CH=C - CH=C -CH2 - etinyl prop-2-inyl

c. ng phn

Cc hirocacbon cha no c cc loi ng phn:

- ng phn v cu to mch cacbon

Th d:CH3-CH-CH=CH2 CH3-CH2-CH2-CH=CH2

CH33-metyl but-1-en pent-1-en(isopentylen) (pentylen)

- ng phn v v tr lin kt kp

CH3 -CH2 -C=CH CH3 -C=C -CH3

but-1-in but-2-in


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- ng phn hnh hc

CH3

CH2 -CH3H

C =CH CH3 CH2 -CH3

H

C =C

H trans-pent-2-en cis-pent-2-en

2.2. Phng php iu ch

a. i t dn xut halogen

Cc hirocacbon cha no c th iu ch bng cch loi HX ca dn xut halogen trongmi trng kim/ru:

CH3 -CH -CH -CH3 CH3 - CH =C -CH3 + HBrKOH

ruBr CH3CH3

CH3 -CH2 -CHCl2 CH3 - C =C + 2 HClKOHru

CH2 -CH2 -CH2 -CH2 CH2 = CH -CH =CH2 + 2 HBrKOHru

Br Br

b. i t ancol

Cc hirocacbon cha no c th iu ch bng cch loi nc ca ancol trong iu kin cH2SO4 c lm cht ht nc nhit trn 170

0C.

H2SO4 CH3 -CH2 -OH CH2 = CH2 + H2O

OH

>1700C

CH3 -CH -CH2 -OH CH3 - C = CH + 2H2OH2SO4

>1700C

OH

CH2 -CH2 -CH2 -CH2 CH2 = CH - CH =CH2 + 2H2OH2SO4

>1700COH

Khi c mt Al2O3 v nhit thch hp c th tng hp c but-1,3-ien t ancol etylic.

Al2O3CH2 = CH - CH =CH2 + 2H2O + H2t0

2 CH3 -CH2 -OH

c. Cc phng php ring iu ch axetilen

CaC2 + 2 H2O Ca(OH)2 + C2H2Trngi hc Nng nghip H Ni - - Gio trnh Ho hu c..4343


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15000C2 CH4 CH =CH + 3 H2

2.3. Tnh cht vt l

Cc anken t C2H4 n C4H8 l cht kh, t C5H10 n C16H32 l cht lng, cn li t C17H34tr ln l nhng cht rn. Cc anken c nhit si v nhit nng chy thp hn so vi ankantng ng. Nhit si ca ng phn cis cao hn ng phn trans, cn nhit nng chy thngc li.

Cc ankin tnh cht vt l cng tng t nh anken. Khi trng lng phn t ca cc ankintng ln th nhit si v nhit nng chy, t trng cng tng.

2.4. Cu to

a. Cu to ca cc ankenHai nguyn t cacbon lin kt i trng thi lai ho sp2. Ba obitan lai ho sp2 ca nguyn

t cacbon ni i hnh thnh ba lin kt , trong c mt lin kt (C-C) hnh thnh do sxen ph ca obitan sp2- sp2 v hai lin kt khc c th l lin kt (C-H) do s xen ph caobitan sp2- s hoc lin kt (C-C) do s xen ph ca obitan sp2 ca cabon ni i v sp3 cacacbon. Mi nguyn t cacbon lin kt i cn li mt obitan 2pz cha tham gia lai ho, chngc trc vung gc vi mt phng cha lin kt , song song vi nhau, c spin ngc chiu nhau,chng xen ph vi nhau hnh thnh lin kt . Do lin kt i gm mt lin kt v mt linkt . V trong phn t c cha lin kt km bn, d dng b ph v tham gia cc phn ngcng hp, oxi ho v trng hp.

H H

HHC C

Hnh 2-3. Lin kttrong phn t etylen Hnh 2-4. Lin kttrong phn t etylen

b. Cu to ca ankaienCc ankaien c cu to tng t nh anken. Ring cc ankaien lin hp cc in t

lin hp vi nhau to thnh mt obitan phn t duy nht gii to trn ton b h lin hp.

H

H

H

H

H

H

Hnh 2-5: Lin kttrong phn t but-1,3-ien



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c. Cu to ca ankin

Hai nguyn t cacbon lin kt ba trng thi lai ho sp. Hai obitan lai ho sp to thnhhai lin kt , trong c mt lin kt (C-C) hnh thnh do s xen ph ca hai obitan lai ho

sp, v mt lin kt , do s xen ph ca obitan lai ho sp ca cacbon ni ba vi obitan s canguyn t hir hoc hnh thnh do s xen ph ca hai obitan lai ho sp vi sp3.Mi nguyn t cacbon ni ba cn li hai obitan p cha tham gia lai ho, chng c trc

vung gc vi mt phng cha lin kt , song song vi nhau v c spin ngc chiu nhau. Ccobitan p ny xen ph vi nhau tng i mt hnh thnh nn hai lin kt . Cc lin kt km bnnn cc ankin l hp cht hot ng ho hc mnh, d dng tham gia cc phn ng cng hp, xiho, phn ng trng hp.

HH

Hnh 2-6: Cc lin kttrong phn t axetilen Hnh 2-7: Cc lin kttrong phn t axetilen

2.5. Tnh cht ho hc

Trong phn t ca tt c cc hirocacbon cha no u c lin kt km bn, lin kt ny bphn cc ho mnh bi cc hiu ng in t c trong ni b phn t, bi tc nhn phn ng viu kin phn ng, do vy cc hirocacbon cha no d dng tham gia phn ng cng hp, phnng oxi ho, phn ng trng hp.

a. Phn ng cng hp vo lin kt kp

Phn ng cng hp xy ra lin kt , chng hn phn ng cng hp ca anken xy ra theos tng qut sau:

+ A+B-+C C

C C

A

B

y AB c th l X2, HOH, HX, HOX, H2SO4

Phn ng xy ra theo c ch cng hp i in t qua hai gia on:

- giai on u, tc nhn i in t (cation A+) cng hp vo nguyn t cacbon mangphn in tch m ni i to thnh cacbocation trung gian. y l giai on chm,thun nghch, quyt nh tc phn ng.

AB A+ + B-



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+ A++C C

C C

A+chm

- giai on sau, cacbocation trung gian tc dng vi anion B - cho sn phm. Giai on

ny phn ng xy ra nhanh, mt chiu.

+ B- C C

A

C C

A+

B

nhanh

Sau y ta xt mt s phn ng cng hp c th:

- Phn ng cng hp halogen

+ X2C C C CXX

y X2 l F2, Cl2, Br2, I2.

Th d:

Br

CH3 -CH =CH2 + Br2 CH3 -CH -CH2

Br

Br

CH2 =CH -CH =CH2 + Br2 CH2 -CH -CH =CH2 + CH2 -CH =CH -CH2

BrBr Br

2 2

BrBr

Br2CH3 -C =CH CH3 -C =CH CH -C -CHBr2

BrBr

BrBr

Phn ng cng hp Br2 c dng nhn bit lin kt kp.

- Phn ng cng hp hiro halogenua (HX)

Tt c cc hirocacbon cha no u d dng cng hp vi HX.

+ HX+C C

C C

HX Th d:

+ CH3 -C = CH -CH3 + HBr CH3 -C -CH2 -CH3

Br

CH3CH3



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C ch cng hp i in t:HBr H+ + Br-

CH3 -C -CH2 -CH3 + Br CH3 -C -CH2 -CH3

CH3CH3

Br

+ CH3 -C = CH -CH3 + H CH3 -C -CH2 -CH3

CH3CH3

Cc ankaien lin hp cng hp vi hirohalogenua bao gi cng cho hai loi sn phm

cng hp 1,2 v cng hp 1,4.

Th d:

CH3 Br

CH2

=C - CH =CH2

+2 HBr CH3

-C -CH =CH2

+ CH3

-C =CH -CH2

CH3CH3

Br

2

C ch phn ng:HBr H+ + Br-

CH2 C - CH CH2 + H++

CH3 - C CH CH2CH3 CH3

Trong cacbocation lin hp in tch dng gii to trn c ba nguyn t cacbon, nhng tptrung hn l C2, C4.

2 ++CH3 C CH CH2 + 2Br- CH3 - C CH CH2Br

CH3 - C CH CH2BrCH3 CH3 CH3

Hirohalogenua cng hp vo ankin s cho sn phm l gem ihalogen ankan.Th d:

CH3 -C=C -CH3 CH3 -C =CH -CH3 CH3 -C -CH2 -CH3+ HCl+ HCl

Cl Cl

Cl

- Cng hp ncTrong mi trng axit cc anken v ankaien cng hp nc to ra cc ancol.

+ HOHC C C CHH OH

Th d:

H

OHCH3 -CH =CH2 + H2O CH3-CH - CH3

H

CH2 =CH -CH =CH2 + H2O CH3 -CH = CH -CH2 -OH



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Khi c mt ca xc tc Hg2+ v axit mnh (H2SO4), cc ankin phn ng vi nc to thnhenol, cht ny khng bn chu s ng phn ho to thnh hp cht cacbonyl. Nu ankin laxetilen s thu c anehit axetic, cn ankin l ng ng ca axetilen thu c xeton.

Th d:

Hg

2+

H2SO4CH = CH + H2O CH2=CH - OH CH3 -CHOchuyn v

OH

Hg2+

H2SO4 OCH3 -C = CH + H2O CH3-C= CH2 CH3 -C -CH3

chuyn v=

b. Phn ng oxi ho

Ph thuc vo iu kin ca phn ng cc hirocacbon cha no c th b oxi ho to thnhcc sn phm khc nhau: poli ancol, anehit, xeton, axit,

nhit bnh thng cc hirocacbon cha no b oxi ho bi dung dch KMnO4 hocdung dch H2O2 trong mi trng axit yu to thnh poli ancol.

Th d:

+ KOH + MnO2CH3 - Ch = CH2 +KMnO4 +H2O CH3 - CH -CH2oh oh

+ KOH + MnO2CH2 =Ch - CH = CH2 +KMnO4 +H2O CH2 - CH -CH-CH2ohoh oh oh

+ KOH + MnO2CH2 =Ch - CH = CH2 +KMnO4 +H2O CH2 - CH -CH-CH2ohoh oh oh

Vi tc nhn oxi ho mnh nhhn hp KMnO4 + H2SO4 hoc K2Cr2O7, cc hirocacbon

ch

a no b oxi ho cho sn phm l axit cacboxylic, xeton v cacbon ioxit.Th d:

CH3 - Ch =CH - CH3 2 CH3 - COOH + H2O

CH2 =Ch - CH = CH2 HOOC -COOH + 2CO2 + H2O

Ch3 - C = CH2 CH3 - C -CH3 + CO2 + H2O

K2Cr2O7 +H2SO4

K2Cr2O7 +H2SO4

=

O

K2Cr2O7 +H2SO4

CH3 Nhng phn ng ny c dng xc nh v tr ca lin kt i trong phn t anken hoc

ankaien.

Khi b oxi ho bi ozon (O3), lin kt i trong phn t anken b t ra to thnh nhng hpcht cacbonyl.Th d:

CH3 - Ch =CH - CH3 CH3 - CH CH -CH3O

O O

+ O3H2O 2 CH3CHO + H2O2



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CH2 =Ch - CH = CH2 CH2 CHO

O O+ O3

H2O 2HCHO + OHC -CHo + H2O2

- CH CH2

O

O O

Ch3 - C = CH -CH3 =OCH3

CH3 - C -CH3CH3 - C CH -CH3O

O O

+ O3H2O

CH3CHO + H2O2+

CH3

Khi c mt cht xc tc Ag kim loi 150 -3500C hirocacbon cha no b oxi ho bi oxikhng kh to thnh ete oxit.

Th d:

CH2 =CH2 + O2 CH2 CH2Ag

1500-3500C

O

Ag1500-3500C

O

CH3

CH2 =C - CH =CH2 +O2 CH2 C - CH CH2

O

CH3 Phn ng oxi ho ng vai tr quan trng trong vic xc nh cu to ca nhng hp cht t

nhin phc tp v xc dnh cu to ca nhng hp cht cha lin kt i.

c. Phn ng trng hp

Phn ng trng hp l phn ng to thnh hp cht cao phn t t nhng phn t n gin.

Th d:n CH2 =CH2 n ( - CH2 - CH2 -) (-CH2 -CH2 -)n

1900-2100C

1500-2000attylen pli tylen

n ( -CH2 -CH =CH -CH2 -) (-CH2 -CH =CH -CH2 -)nn CH2 =Ch - CH = CH2cao su buna

d. Phn ng th

Nhng ankin c cha nguyn t hiro lin kt vi cacbon trng thi lai ho sp c th thamgia phn ng th. Nguyn t hiro c thay th bi nguyn t kim loi to thnh mui. Trongphn ng ny ankin th hin tnh axit. iu ny c gii thch do nguyn t cacbon trng thi

lai ho sp c m in ln, lin kt Csp-H b phn cc mnh.

Kali hiroxit khan c th chuyn ankin-1 thnh kali axetilua, tuy nhin phn ng ny xy rathun li hn nu ta dng kali amiua trong amniac lng.

NH3 lngR -C =CH + KNH2 R -C =C -K + NH3

Cc ankin -1 v axetilen d dng phn ng vi phc bc amoniacat cho kt ta bc axetilua.



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R -C =CH + 2[Ag(NH3)2]OH R -C =C Ag + 2NH3 + H2O

HC =CH +2[Ag(NH3)2]OH AgC =C Ag + 4 NH3 +2 H2O

3. hirocacbon thm

Hirocacbon thm l nhng hirocacbon c cha nhn benzen trong phn t.

Da vo cu to ngi ta chia hirocacbon thm thnh hai loi:

- Hirocacbon thm mt nhn- Hirocacbon thm nhiu nhn

3.1. Hirocacbon thm mt nhn benzen

Hirocacbon thm mt nhn benzen c cng thc chung CnH2n-6 (n6), k hiu Ar-H.

Gc hirocacbon thm ho tr mt c tn gi l gc aryl, k hiu Ar-Th d:

C6H5- C6H5-CH2-phenyl benzyl

a. Cch gi tn v ng phnNgi ta thng dng tn gi hp l gi tn ng ng ca benzen. Theo tn gi ny

ng

i ta ly cht gc l benzen, cn cc ng ng khc ca benzen

c coi l dn xut th cabenzen khi th nguyn t hir trong nhn benzen bng gc ankyl v gi tn theo nguyn tc:

Tn gc ankyl +benzen

Ngoi ra mt s ng ng khc ca benzen cn c gi tn theo tn gi h thng.

Th d:CH3

CH -CH3CH3

metylbenzen isopropylbenzen(toluen) (cumen)

CH3

CH3

CH3

CH3

CH3

CH3

o-xilen p-xilen m-xilen



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Nhn thm c hai nhm th ankyl tr ln th hnh thnh ng phn v v tr nhm th. gi tn cc ng phn ngi ta tin hnh nh s cc nguyn t cacbon ca vng benzen. Bt unh s t nguyn t cacbon trong vng benzen lin kt vi nhm th n gin nht. nh stheo chiu sao cho tng cc con s ch v tr nhm th l nh nht. Gi tn theo nguyn tc:

V tr nhm th + tn nhm th + benzen

Th d:

CH2 -CH3

CH3

CH2 -CH3

CH3

CH2 -CH3

CH3

1-metyl-2-etylbenzen 1-metyl-3-etylbenzen 1-metyl-4-etylbenzen

Ngi ta qui c v tr s 2 v s 6 c gi l v tr octo (vit tt l o-), v tr s 3 v s 5c gi l v tr meta (vit tt l m-), v tr s 4 gi l v tr para (vit tt l p-). Theo qui c cc ng phn trn c gi tn tng ng l o-etyl toluen, m-tyl toluen,p-etyl toluen.

Vi cc dn xut ca benzen nhng nguyn tc c bn trn y vn c p dng.

Th d:

NO2 Cl

nitrobenzen clobenzen NO2

Cl

Br

Br

Br

1,2-ibrom benzen 3-clo-5-brom nitrobenzen

Tuy nhin nhiu benzen th mt ln mang tn h thng v chng ph bin rt rng ri ihi chng ta phi nh.

Th d:

NH2 OH OCH3 CHO COOH

anilin phenol anisol benzanehit axit benzoic



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Cc ng ng ca benzen c hai loi ng phn:

- ng phn v cu to mch nhnh.

CH2 - CH2 -CH3 CH -CH3CH3

n- propylbenzen isopropylbenzen- ng phn v v tr nhm th

CH3

CH3

CH3

CH3

CH3

CH3

1,2-imetylbenzen 1,3-imetylbenzen 1,4-imetylbenzen

b. Phng php iu ch

Benzen c iu ch bng phn ng trng hp ba phn t axetilen 6000C.

3 CH =CH 6000C

C Cc ng ng ca benzen c iu ch bng hai phng php chnh sau y:- Phn ng Vuyc-Fittic

Ar -X + 2Na + X -R Ar -R + 2NaX Th d:

ClCH3

+ 2Na + Cl -CH3 + 2NaCl

- Phn ng Frien-CrapR

+ RX HXAlCl3

Th d:

CH2 -CH3

AlCl3+CH3 -CH2 -Cl HCl

c. Tnh cht vt l

Phn ln cc hirocacbon thm l nhng cht c mi c trng. Cc ng phn khc nhauv v tr ca gc ankyl trong nhn benzen c nhit si gn ging nhau, nhng nhit nngchy li khc nhau rt nhiu. Cc ng phn para c im nng chy cao nht.



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d. Cu to ca benzen

Tt c cc hirocacbon thm u c cha nhn benzen. V vy vic nghin cu cu to cabenzen cho php hiu v cu to ca cc hirocacbon thm.

- Cu to phn t benzen theo Kkul:Ben zen c cng thc C6H6. Theo Kkul cu to ca benzen l nh sau:

Cu to ny th hin s khng no rt ln, ngha l n d dng tham gia phn ng cng hpv kh i vi phn ng th. Ngc li, benzen tng i tr vi cc tc nhn oxi ho, d thamgia phn ng th, kh tham gia phn ng cng hp.

- Cu to phn t benzen theo quan im hin i:

Benzen c cu to vng 6 cnh phng, tt c 6 nguyn t cacbon v 6 nguyn t hiro unm trn mt phng . Cc nguyn t cacbon u trng thi lai ho sp2, l kiu lai ho tamgic, gc lai ho 1200. Mi nguyn t cacbon to thnh ba lin kt , trong c hai lin ktC-C (sp2-sp2) v mt lin kt C-H (sp2-s).

Mi nguyn t cacbon cn li mt obitan 2pz cha tham gia lai ho. Cc obitan ny vunggc vi mt phng cha lin kt (mt phng vng benzen), c spin ngc chiu nhau. Tt c 6obitan 2pz ny xen ph, pha ho ln vo nhau, lin hp vi nhau to thnh mt obitan phn tkhp kn. Do s lin hp nh vy lm cho khong cch gia cc nguyn t cacbon trong phn tu bng nhau (1,40A0), vng tr nn bn vng kh tham gia phn ng cng hp, bn vi tcnhn oxi ho v d tham gia phn ng th. c tnh ny ca benzen c gi l tnh thm.

CC

C CC

Ch

h

h

h

h

h

Cc lin kt trong phn t benzen

biu din cng thc cu to ca benzen ta c th dng mt trong ba cng thc sau:



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c. Tnh cht ho hc

- Phn ng th

Benzen v ng ng ca benzen d dng tham gia phn ng th nguyn t hiro trong nhnthm bng nguyn t hoc nhm nguyn t khc.

Phng trnh phn ng tng qut:

Ar -H + AB Ar -A + HBxt

Phn ng xy ra theo c ch th i in t (electrophin) hai giai on.

Giai on u, tc nhn i in t ( cation A+) tn cng vo h thng in t trong nhn,mt cp in t c A nhn to thnh lin kt vi mt nguyn t C, trong nhn cn li haicp in t c gii to ng u trn nm nguyn t cacbon cn li. Sn phm trung giankhng bn ny c gi l phc .

HAr -H + A Ar - A

chm

Giai on sau, phc loi proton cacbon b th to thnh sn phm.

Ar A Ar A + H

H+ +

Sau y ta xt mt s phn ng c th.

- Phn ng halogen ho

L phn ng thay th nguyn t hiro trong nhn benzen bng nguyn t halogen. Tc nhnca phn ng l halogen v xc tc thng dng l cc axit liuyt nhAlCl3, FeX3.

Trong thc t phn ng ny thng dng xc tc l bt st. Bt st tc dng vi cc halogento thnh cc axit liuyt l FeX3.

S phn ng tng qut nh sau:X

+ X2 + HXFe bt

Cl2 v Br2 halogen ho benzen mt cch bnh thng, I2 phn ng thun nghch, F2 khng

phn ng trc tip vi benzen.



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Th d:Br

+ Br2 + HBrFe bt

CH3

Br

+ 2Br2 + 2HBrFe bt

CH3Br

CH3

+

Tc nhn i in t c to thnh nh sau:2 Fe + 3 X2 2FeX3

FeX3 + X2 X. ..... X. ....FeX3 FeX4 + X

Sau phn ng xy ra. HX

X

H+ X ++

++

iu kin nhit cao hoc chiu nh sng t ngoi, cc ng ng ca benzen thc hinphn ng halogen ho phn nhnh theo c ch th gc tng t cc ankan.

Th d:

CH -CH3CH3

+ Cl2 + HClC -CH3

CH3

Cl

ht0

- Phn ng nitro ho

Tc nhn phn ng thng dng l hn hp nitro ho ( HNO3 c + H2SO4 c).

Th d:

H2SO4NO2

++HNO

3H

2O

Tc nhn i in t NO2+ c to ra do phn ng:

HNO3 + 2H2SO4 NO2 + 2HSO4 + H3O

+ NO2HNO2+

NO2

+ H



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H + 2HSO4 + H3O H2SO4 + H2O

- Phn ng ankyl ho

C th ankyl ho hirocacbon thm bng cc tc nhn ankyl halogenua, anken, vvKhidng tc nhn ankyl halogenua cn c xc tc l AlCl3 khan hoc FeCl3 lm xc tc.

+R -X + HX

RAlCl3

Tc nhn i in t R+ c to thnh do:

+ +-AlCl3 + RX AlCl3 ....X....R AlCl3X + R

R

H

+ H++ R+ R

+

R

+

H+ + AlCl3X- HX + AlCl3

- Phn ng axyl ho

Tc nhn axyl ho thng dng l axyl halogenua R-CO-X, xc tc l AlCl3.

=

OR -C -X+

=

OC -R

HX+

Tc nhn i in t c hnh thnh v c ch phn ng xy ra nh sau:

R -C -Cl + AlCl3 R -C ...Cl ....AlCl3+

=

O=

O

R -C + AlCl4=O

+ -

OR -C O

H

O H=+

+=C -R+ =C -R ++

H+ + AlCl4

- HCl + AlCl3

+ Quy tc th i in t trong nhn thm

Khi trong nhn thm c sn nhm th th cc nhm th ny s nh hng n s th tiptc v hai phng din:

- Lm tng hay gim tc phn ng th- Hng tc nhn th vo v tr nht nh i vi nhm th c sn.



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iu c quyt nh ch yu l do bn cht in t ca nhm th. C th phn chia ccnhm th thnh hai loi nh sau:

- Nhng nhm th nh hng octo v para gm c: -R, -X, -OH, -NH2, -NHR, -NR2, -NH-CO-R

Nhng nhm th ny u hot ho nhn thm (tr nhng nguyn t halgen X), do chngc ng thi hiu ng cm ng dng (+I) v hiu ng siu lin hp (-) hoc hiu ng lin hpdng (+C) ln hn hiu ng cm ng m (-I) lm cho mt in t trong nhn benzen tng lnv tng ch yu cc v tr octo v para. Do vy phn ng xy ra d dng hn v cho sn phmth v tr octo v para.

Th d:

C H

HH

+I

+C

-I

NH2 +C

-I

OH

Khi nhn benzen c mt nguyn t halogen, mt in t trong nhn gim i bi nguyn

t halogen gy hiu ng cm ng m (-I) mnh hn hiu ng lin hp dng (+C). Tc phnng th i in t chm hn so vi benzen, nhng nguyn t halogen vn thuc nhm th nhhng octo v para, v hiu ng lin hp dng (+C) quyt nh chiu phn cc ca lin kt kplm cho mt in t cc v tr octo v para ln hn v tr meta.

+C-I

Cl

- Nhng nhm th nh hng meta: Gm c -CN, -NO2, -CH=O, -COR, -COOH, -COORNhng nhm ny c ng thi hai hiu ng ht in t (-I, -C) lm mt in t trong

nhn gim i, phn hot ho nhn thm v gim ch yu cc v tr octo v para. Phn ng thxy ra kh khn hn so vi benzen v cho sn phm th v tr meta.

Th d:

CO

H

-C

CO

OH

-C

-I -IN

O

O

-C

-I

S tn ti hai nhm th trong vng benzen lm phc tp ho tc dng nh hng. C thtin on hng ca phn ng da theo nguyn tc sau: Nu trong vng benzen tn ti hai nhmth cng hot ho vng hoc c tc dng nh hng khc nhau th nhm hot ho mnh skhng ch hng ca nhm th th ba.



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- Phn ng cng hp

Phn ng cng hp ph v h lin hp ca nhn thm xy ra tng i kh khn so vi cnghp vo anken.

- Cng hp hiro: Phn ng xy ra khi c xc tc Ni, Pt, Pdta thu c xiclo ankan tng ng.

Th d:

3 H2+

benzen xiclohexan

CH3

+3H2

CH3

toluen metyl xiclohexan

- Cng hp halogen: Quan trng hn c l phn ng cng hp clo. Khi cho clo i quabenzen c chiu nh sng khuch tn, phn ng xy ra ta thu c hexaclo xiclohexan.

+ 3 Cl2 h500C Cl

Cl

ClCl

Cl

Cl

Hexaclo xiclohexan c nhiu ng phn lp th, trong ng phn gamma () c hot tnh

c i vi cn trng, v vy ng phn ny c dng lm thuc tr su (c tn gi l thuc tr

su 6.6.6). Hin nay thuc tr su ny c cm s dng do s tn lu lu di v gy c hii vi mi trng.

Phn ng oxi ho

Benzen ch b oxi ho khi cho oxi khng kh tc dng nhit cao, c V2O5 xc tc tothnh anhirit maleic.

+ O2 V2O5+ CO2

4000C-4500C

C O=

CO

=

O

anhirit maleic

Benzen cng tham gia phn ng ozon ho to thnh glioxal.

+ O3H2O CHO

CHO3 + H2O2



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Vi cc cht oxi ho mnh: KMnO4 +H2SO4, K2Cr2O7 +H2SO4cc ng ng ca benzenb oxi ho mch nhnh, ct t lin kt C - C v oxi ho chng thnh nhm chc axit.

Th d:

COOHCH2 -CH2 -CH3+ KMnO4 + H2SO4 + CH3COOH + K2SO4 + MnSO4 + H2O

t0

n- propyl clorua axit benzoic

COOHCH3

+ KMnO4 + H2SO4 + CH3COOH + K2SO4 + MnSO4 + H2Ot0CH3

COOH

o-xilen axit o- phtalic

3.2. Hirocacbon thm nhiu nhn

Hirocacbon thm nhiu nhn cn gi l hirocacbon thm a vng. Chng c chia lm hailoi:

- Hirocacbon thm a vng ri rc

Th d:

- CH2 -

iphenyl iphenylmetan

- Hirocacbon thm a vng ngng t

Th d:

naphtalen anthraxen

a. Hirocacbon thm a vng ri rc

- i phenyl

i phenyl c th c iu ch t dn xut monohalogen thm bng phn ng Fittic.



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Th d:

++2NaBr Br + 2NaBr

iphenyl l nhng tinh th rn, khng mu, nng chy 710C, tan tt trong etanol v ete.

iphenyl cng tham gia cc phn ng th i in t nhnitro ho, halogen ho

u tin phn ng v tr 4, sau l v tr 4.

Th d:

NO2HNO3H2SO4

O2N NO2

b. Hirocacbon thm a vng ngng t

- Naphtalen (bng phin)

12

345

6

7

10

89

Naphtalen nguyn cht l cht kt tinh thnh nhng l mng ng nh, nng chy 80,3 0C

v si 2180C, c mi thm c trng, d bay hi v d thng hoa.

Naphtalen ging benzen nhiu phn ng, nhng kh nng phn ng ca naphtalen mnhhn benzen.

Nhng phn ng th c th xy ra v tr (v tr 1, 4, 5 hoc 8)

Th d:

NO2

+ HNO3 + H2O

Khi b oxi ho, naphtalen bin thnh anhirit phtalic.

V2O5, 4500C

=

=

CO

CO

OO2 +2 H2O



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- Phenanthren

Phenanthren l cht rn kt tinh di dng tinh th khng mu, nng chy 1010C v si 3400C. Phenanthren c tnh cht ho hc tng t nh naphtalen. Phenanthren rt gn vi nhiuhp cht t nhin c hot tnh sinh l quan trng nhvitamin D, cc kch thch t sinh dc.



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Cu hi v bi tp

1. C ch th gc t do v hng ca phn ng halogen ho ankan? Gii thch bn ca

cc xicloankan.2. Cu to v tnh cht ca cc hirocacbon khng no. C ch cng hp i in t v hngca phn ng cng hp vo lin kt i C=C; lin kt ba CC.

3. Cu to ca benzen. Tnh thm v tnh cht ho hc ca cac hirocacbon thm. C chth i in t v quy lut th trong nhn thm.

4. Gi tn cc hp cht sau y theo tn gi thng thng v tn gi IUPAC.4.1. CH3- CH2- CH2- CH2- CH34.2. CH3- CH- CH2- CH2- CH3

CH3CH3

4.3. CH3- C- CH2- CH2- CH3CH3

4.4. CH3- C=CH2CH3

CH3- CH2- CCH5. Vit cng thc cu to ca cc hp cht sau:

5.1. 2,5-imetyl octan5.2. neoheptan5.3. 2,5,5-trimetyl hept-3-en5.4. isopropylbenzen

6. Vit cng thc cu to cc ng phn ca cc hirocacbon c cng thc phn t C6H14;C5H10 v gi tn chng theo tn gi IUPAC.

7. Vit phng trnh v c ch cc phn ng sau:

7.1. 2-metyl propan + Cl2 askt

7.2. 2-metyl butan + Cl2 askt

7.3. isopropyl benzen + Cl2 )t

7.4. 2-metyl buta-1,3-ien + HCl 7.5. Pent- 2-en + HCl 7.6. Vinyl clorua + HCl 7.7. Bezen + HNO3 7.8. Toluen + Br2

Fe

8. Hon thnh cc phng trnh phn ng ho hc sau:8.1. 2-metylpropen + KMnO4 + H2O

8.2. Axetilen + KMnO4 + H2O )t

8.3. isopropyl benzen + KMnO4 + H2SO48.4. Buta-1,3-ien + O3

9. Cho bit cng thc cu to v gi tn cc hp cht c cng thc phn t:9.1. C5H12; c mt nguyn t cacbon bc 3.



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9.2. C4H8; khi cho tcdng vi dung dch KMnO4 thu c ru hai chc, trong cmt nhm chc ru bc mt v mt nhm chc ru bc 3.

9.3. C9H12; khi halogen ho nhit cao thu c dn xut halogen bc 3.

9.4. C5H

10; oxi ho bng ozon, sau thu phn thu c anehit axetic v axeton.

10. T benzen v cc hp cht khc, hy vit phng trnh phn ng ho hc dng iu ch:10.1. Axit o v m nitro benzoic.10.2. Metyl phenyl xeton.10.3. 2-clo- 2- phenylpropan.10.4. p v m clo nitrobenzen.


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Chng III

Dn xut ca hirocacbonDn xut ca hirocacbon l nhng hp cht m trong phn t ca chng cha mt hay mt

s nhm chc lin kt vi gc hirocacbon.

Da vo bn cht ca nhm chc m dn xut ca hirocacbon c chia thnh nhng loikhc nhau. Th d dn xut halogen, ancol, ete, axit cacboxylic vv

Trong ni dung chng ny chng ta ch xt mt s dn xut quan trng, l dn xuthalogen, anc

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Giáo trình Hóa học hữu cơ - Đinh Văn Hùng