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Chapter 1 Introduction to Organic Chemistry:Chapter 1 Introduction to Organic Chemistry:
1.1 Organic Compounds
1
Organic ChemistryOrganic Chemistry
An organic compound
• is a compound made from carbon atoms.• has one or more C atoms. • has many H atoms.• may also contain O, S, N, and halogens.
2
Organic ChemistryOrganic Chemistry They are everywhere in our daily life
◦ foods, flavors and fragment◦ Medicines, toiletries and cosmetics◦ Plastics, films, fibers and resins◦ All other living organisms
Organic CompoundsOrganic Compounds
Typical organic compounds
• have covalent bonds.
• have low melting points.
• have low boiling points.
• are flammable.
• are soluble in nonpolar solvents.
• are not soluble in water.
4
oil (organic) and water (inorganic)
Organic vs. InorganicOrganic vs. Inorganic
• Propane, C3H8, is an organic compound used as a fuel.
• NaCl, salt, is an inorganic compound composed of Na+ and Cl− ions.
Why is propane organic,but NaCl is not?
5
ExamplesExamples
Identify each characteristic as most typical of compounds
that are 1) inorganic or 2) organic.
A. has a high melting point.
B. is not soluble in water.
C. has a formula CH3─CH2─CH3.
D. has a formula MgCl2.
E. burns easily in air.
F. has covalent bonds.
6
1.2 Where do we obtain Organic 1.2 Where do we obtain Organic compounds?compounds?
Two principal ways: ◦ isolation from nature
is to extract and purify them from biological sources
◦ synthesis in the laboratory
Synthesis in the Laboratory Synthesis in the Laboratory Using different methods to made an organic compound or
develop their derivatives
Lewis StructuresLewis Structures represents how an atom’s valence electrons are
distributed in a molecule
Show the bonding involves (the maximum bonds can be made)
Try to achieve the noble gas configuration
The valence-shell electron-pair repulsion (VSEPR) model tell us the common angles about the carbon atoms
Writing Dot Lewis Structure: Rules Writing Dot Lewis Structure: Rules for multiple atomsfor multiple atoms Duet Rule: sharing of 2 electrons
◦ E.g H2 H : H
Octet Rule: sharing of 8 electrons◦ Carbon, oxygen, nitrogen and fluorine always obey
this rule in a stable molecule◦ E.g F2, O2
Bonding pair: two of which are shared with other atoms
Lone pair or nonbonding pair: those that are not used for bonding
1.3 How do We Write Structural 1.3 How do We Write Structural Formulas of Organic Compounds?Formulas of Organic Compounds?
A hydrogen molecule
• is stable with 2 electrons (helium).
• has a shared pair of electrons.
12
Multiple BondsMultiple BondsIn a nitrogen molecule, N2,
• each N atom shares 3 electrons.• each N attains an octet.• the bond is a multiple bond called a triple
bond.• the name is the same as the element.
13
Carbon Forms 4 Covalent BondsCarbon Forms 4 Covalent Bonds
Carbon normally forms four covalent bonds and has no unshared pairs of electrons
E.g In a CH4 (methane) molecule,
• 1 C atom shares electrons with 4 H atoms to attain an octet.
• each H atom shares 1 electron to become stable, like helium.
Bonding in Methyl Cation, the Bonding in Methyl Cation, the Methyl Radical, and the Methyl Methyl Radical, and the Methyl AnionAnion Not all carbon atoms form four bonds
C
carbocation
C
Carboanion
C
Carbo radical
General rules for Writing Dot Lewis structure General rules for Writing Dot Lewis structure involving N, O, H and Halogens involving N, O, H and Halogens
Nitrogen normally forms three covalent bonds and has one unshared pair of electrons
Oxygen normally forms two covalent bonds and has two unshared pairs of electrons
A halogen (fluorine, chlorine, bromine, and iodine) normally forms one covalent bond and has three unshared pairs of electrons
N
O
X
16
Some Electronegativity Values for Group A Some Electronegativity Values for Group A ElementsElements
Low values
High values
` Electronegativity increases
` E
lectro
neg
ativ
ity d
ecre
ase
s
Copyright © 2009 by Pearson Education, Inc.
Polar Covalent Bonds: ElectronegativityPolar Covalent Bonds: Electronegativity
NaCl
HCl
Cl2
Writing Dot Lewis Structure with Writing Dot Lewis Structure with multiple center atomsmultiple center atoms Carbons will also be the center atom in the organic
molecule◦ -C-C-C- chains
Hydrogen is connected to carbon unless it’s an oxyacids (HClO, etc..) or Carbon has no more valence electrons to share
Order of increasing EN◦ (least) C N O F (most)
ExamplesExamples Write a Dot Lewis structure for the following atoms,
molecules and ions O N H2S CN-
CO32- C2H2
N2H4 CH2Cl2
Write a Dot Lewis structure for CH3COOH
Total Valence electron:H = 4 x1 = 4C = 2 x 4 = 8O = 2 x 6 = 12Total = 24
SkeletalC is less electro negative than OO does not bond to O
H C
H
H
C
O
O H
Bonding
C C O
O
H
H
H
H
Total e- = 24
bonding e - = 14
e- lef t = 10
C C O
O
H
H
H
H
Complete Octet
NOT :)) must form multiple bond
C C O
O
H
H
H
H
Total = 24 e-Bonding = 16Nonbonding = 8e- lef t = 0
Correct
ExampleExampleWrite a Dot Lewis Structure for
CH3NH2
VSEPR TheoryVSEPR Theory VSEPR theory proposes that the geometric
arrangement of terminal atoms, or groups of atoms about a central atom in a covalent compound, or charged ion, is determined solely by the repulsions between electron pairs present in the valence shell of the central atom
Common shape and angles◦ Linear (180o)◦ Tetrahedral (109.5o)◦ Trigonal planar (120o)
See table 1.2 page 5
ExamplesExamples Complete the following Dot Lewis structure by adding
the missing lone-pair then predict the bond angles
a.
b.
c.
C C
H
H Cl
H
H C
O
H
C NC
H
H
H
25
Elements in Organic CompoundsElements in Organic Compounds
In organic molecules, carbon atoms bond • with four bonds.• mostly with H and other C atoms.• sometimes to O, N, S. • sometimes to halogens F, Cl, and Br.• Table 1.3 page 7
26
Functional groups are• a characteristic feature of organic molecules that
behave in a predictable way. • composed of an atom or group of atoms. • groups that replace a hydrogen atom in the
corresponding alkane.• a way to classify families of organic compounds.
Functional GroupsFunctional Groups
AlcoholAlcoholAn alcohol
contains the hydroxyl (-OH) functional group.R-OH
R C
R
R
O H
Functional group
R = H or Carbon group (alkyl)
H3C C
H
H
O H
H3C C
CH3
H
O H
H3C C
CH3
CH3
O H
1o alcohol
2o alcohol
3o alcohol
Types of Alcohol
Writing structural formulas of Writing structural formulas of AlcoholAlcohol
CH4OMolecular formula
CH3OHCondensed formula
C
H
OH
H
H
Structural formualMethanol
Writing structural Formulas of Writing structural Formulas of AlcoholsAlcohols Draw Lewis structure and condensed structural
formulas for the four alcohol with molecular formula C4H10O. Classify each alcohol as primary, secondary or tertiary. ◦ Hints: Consider the connectivity of the four carbon
atoms; they can be bonded either four in a chain or three in a chain with the fourth carbon as a branch on the middle carbon. Then consider which carbon should connect to OH with having the same molecule
AminesAmines
In amines, the functional group is a nitrogen atom. RNH2, R2NH or R3N
H3C N
H
H Methylamine
1o amine
H3C N
CH3
H
H3C N
CH3
CH3
Dimethylamine
2o amine
Trimethylamine
3o amine
N
ExamplesExamples Draw structural formulas of the three secondary
amines with the molecular formula C4H11N
Ketone and AldehydeKetone and Aldehyde Aldehyde contains a carbonyl group bonded to a
hydrogen Ketone contains a carbonyl group bonded to two
carbon atoms
O
CR H
AldehydeR = CH3 or anyhydrocarbons
O
CR1 R2
KetoneR = CH3 or any hydrocarbons
Carboxylic AcidsCarboxylic Acids
Carboxylic acids contain the carboxyl group, which is a carbonyl group attached to a hydroxyl group.
–COOH
O ║
— C—OH
ExamplesExamples Draw condensed structural formulas for the two
carboxylic acids with molecular formula C4H8O2
Carboxylic estersCarboxylic esters An ester contains the carboxyl group between
carbon atoms.
–COOR or –CO2R
C
O
O C
Functional group
ExamplesExamples Draw structural formulas for the four esters with the
molecular formula C4H8O2
37
Learning CheckLearning CheckClassify each of the following as: alcohol, ether, aldehyde, ketone, carboxylic acid, ester, amine, or amide.
1) CH3─CH2─CH2─OH
2) CH3─O─CH2─CH3
3) CH3─CH2─NH2
O O ║ ║
4) CH3─C─OH 5) CH3─C─O─CH3
ExamplesExamples Consider the formula C4H8O2. Write the structural
formula for this molecular formula with ◦ A carboxyl group◦ Ketone group and a 2o alcohol group◦ An aldehyde and a 3o alcohol group◦ A carbon-carbon double bond and a 1o alcohol