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INTRODUCTION TO ORGANIC CHEMISTRY
2
TOPICS 1.1 Introduction to Organic Chemistry 1.2 Alkanes and Cycloalkanes 1.3 Alkenes and Alkynes 1.4 Aromatic Compounds 1.5 Alkyl Halides 1.6 Alcohols 1.7 Aldehydes and Ketones 1.8 Carboxylic Acids and their Derivatives 1.9 Amines
INTRODUCTION TO ORGANIC CHEMISTRY
Structural Formulas of Organic Molecules Ways of Depicting the Organic Molecules Classification of Carbon and Hydrogen
Atoms in Organic Molecules Functional Groups and Homologous
Series Isomerism in Organic Molecules Introduction to Organic Molecules
Reactions
Organic chemistry is a branch of chemistry that focuses on compounds that contain carbon except CO, CO2, carbonates, and carbides
Even though organic compounds only contain a few elements, the unique ways carbon atoms can attach together to form molecules leads to millions of different organic compounds
1.1 Introduction to Organic Chemistry
Organic compounds tend to be molecular
Mainly composed of just six nonmetallic elements C, H, O, N, S, and P
Contains halides group- organohalides
Unique things about carbon atom - can form four bond - bond is very strong and nonreactive - can form long chains - can form rings - bond formed with single, double, or triple
bonds
1.1 Introduction to Organic Chemistry
6
Properties Compounds found in all three states
- solids, liquids, and gases - solids tend to have low melting points
Solubility in water varies depending on which of the other elements are attached to C and how many there are - CH3OH is miscible with water; C10H21OH is insoluble
Hydrophobic part
1.1 Introduction to Organic Chemistry
7
Bonding and Hybridization
1.1 Introduction to Organic Chemistry
sp3
When C has four single bonds, the shape is tetrahedral, carbon sp3
8
Bonding and Hybridization
1.1 Introduction to Organic Chemistry
sp2
When C has two single + one double bond, the shape is trigonal planar, carbon sp2
9
Bonding and Hybridization
1.1 Introduction to Organic Chemistry
sp
When C has one triple + one single or two double bonds, the shape is linear, carbon sp
Structural Formulas of Organic Molecules
Molecular Formula tells us what are the elements and how many atoms of each element are present in one molecule
For example C2H7N C3H8O
Structural Formulas of Organic Molecules
Structural Formula tells us the actual number of atoms and shows the order in which the atoms in the molecule are connected together
For example C2H7N and C3H8O
C C NH
HH
H
H
HH C N C
H
HH
H HH
HFormula I : Ethanamine Formula II : Dimethylamine
C C CH
HH
H
H
HO
HH C O C
H
HH
HC
HH
H
HFormula I :1-Propanol Formula II : Methoxyethane
Ways of Depicting the Organic Molecules
Expanded structural formula shows every atom and type of covalent bond in the molecule
C C CH
HH
H
HO H
OC CH
HH
HCH
HC CH
HH C C
H
HH
Ways of Depicting the Organic Molecules
Condensed structural formula shows every atom and type of covalent bond in the molecule
C C CH
HH
H
HO H
O
C CH
HH
HCH
CH3CH2COOH
C C CH
HH
H
H
H
HCH3CH CH(CH2)2CH3
Ways of Depicting the Organic Molecules
Skeletal structural formula shows the carbon skeleton, the atom hydrogen omitted on carbon, unless hydrogen bound to the heteroatoms.
C C CH
HH
H
H
HN
C C CH
HH
H
HO H
O
C CH
HH
HCH
CH
H
O
OH
NH2
H
H
HH
CC C
CC
H OHH
H HH
H
HHH
OH
Ways of Depicting the Organic Molecules
Skeletal structural formula in 3D 3D geometry of atoms spatial arrangements of atoms or groups of atoms within the molecule. Wedges and dashes to indicate 3D Cl
OH
Cl
HO
Cl
HO
wedge represent a group coming out of the planeof paper
dash represent a groupgoing behind of the plane of paper
solid line represent a grouplying in the plane of paper
Exercise 1 : Write the expanded structural and condensed formula for the straight chain alkane C8H18
Exercise 2 : Write the molecular formula and condensed structures for each of the following compounds
Exercise 3 : Write the carbon skeletal for compounds below
CH3CH2CHCHCCH2COOH
Br
OH
Primary carbon one alkyl group and three atoms hydrogen
Secondary carbon two alkyl groups and two atoms hydrogen
Tertiary carbon three alkyl groups and one atom hydrogen
Quarternary four alkyl groups and no atom hydrogen
Classification of Carbon and Hydrogen Atoms in Organic Molecules
Primary hydrogen three atoms hydrogen attached to primary carbon
Secondary hydrogen two atoms hydrogen attached to secondary carbon
Tertiary hydrogen three atoms hydrogen attached to tertiary carbon
Classification of Carbon and Hydrogen Atoms in Organic Molecules
Exercise 4 : Identify the carbon atoms in the following molecules as primary, secondary, tertiary or quaternary
CH3CHCH2CCH3
CH3
CH3CH3
(a) (b)
Exercise 5 : Identify the hydrogen atoms on the above molecules as primary, secondary, or tertiary
Functional groups is a group of atoms that have a chemical behaviour of the parent molecule.
is the structural unit responsible for a given molecules reactivity under a particular set of conditions.
The group reacts in a typical way, generally independent of the rest of the molecule
Functional Groups and Homologous Series
Functional Groups
Class Functional Group Example
Alkene C C
CH3
H3C CH2Limonene
1.1 Introduction to Organic Chemistry
Alkyne
Class Functional Group Example
Norethindrone
C C
O
COH CCH3
H
Functional Groups
1.1 Introduction to Organic Chemistry
Class Functional Group Example
Alkyl HalideX = F, Cl, Br, I
R X
ClCl
ClCl
Cl
Cl
1,2,3,4,5,6-Hexachlorocyclohexane Lindane
Functional Groups
1.1 Introduction to Organic Chemistry
Class Functional Group Example
Alcohol R OH
CH3
H3C CH3
OH
2-Isopropyl-5-methylcyclohexanol Menthol
Functional Groups
1.1 Introduction to Organic Chemistry
OH3C CH3
(CH2)4CH3HO
H3C
'9-Tetrahydrocannabinol THC
Class Functional Group Example
Ether R O R'
Functional Groups
1.1 Introduction to Organic Chemistry
Class Functional Group Example
Aldehyde
Cinnamaldehyde
OC
R H
CC
CO
H
H
H
Functional Groups
1.1 Introduction to Organic Chemistry
Class Functional Group Example
Ketone
Jasmone
CH3
CH3
OOC
R R'
Functional Groups
1.1 Introduction to Organic Chemistry
Class Functional Group Example
Carboxylic Acid
Ibuprofen
OC
R OHC
CH3
CH3
CH3O
OH
Functional Groups
1.1 Introduction to Organic Chemistry
EsterOC
R OR'
CO
OCH3
OH
Class Functional Group Example
Methyl salicylate
Functional Groups
1.1 Introduction to Organic Chemistry
Class Functional Group Example
Amine
Mescaline
NR R' R"
NH2
OCH3H3CO
H3CO
Functional Groups
1.1 Introduction to Organic Chemistry
Differences between functional groups and class of compound they are not the same!
For example : 2-butanol functional group is (-OH) hydroxyl group .But the class of the compound is alcohol.
Functional Groups and Homologous Series
CH3CH2CHCH3OH
Differences between functional groups and class of compound they are not the same!
For example : Propanal and propanone functional group is (C=O) carbonyl group. But the class of the compound is aldehyde and ketone respectively
Functional Groups and Homologous Series
H3CH2CC
H
O
H3CC
CH3
O
33
Exercise 6: i) Draw any three chain isomers of C7H16 ii) Draw any two positional isomers of C5H12O iii) Draw any one functional isomers of C5H12O
Homologous series a series of organic compounds with similar chemical properties, in which each member differs from previous one by the addition of a CH2- group is called a homologous series
The members of a homologous series are called homologues.
Functional Groups and Homologous Series
General properties - same functional groups and similar chemical
properties - each member differs from next in the series
by a CH2 group - can be prepared by similar methods - physical properties is progressive change
with increasing molecular mass - contain the same elements and represented
by the same general formula
Functional Groups and Homologous Series
General formula - a general formula is a formula that can apply not only to a specific compound but to all compound in the same homologous series.
Some homologous series have the same general formula
- Alkenes and cycloalkanes (CnH2n) - Alkynes and cycloalkenes (CnH2n-2) - Aldehydes and ketones (CnH2nO) - Carboxylic acids and esters (CnH2nO2)
Functional Groups and Homologous Series
Homologous series
General Formula
Example Structural Formula
Alkanes CnH2n+2 C6H14 CH3(CH2)4CH3 Alkenes CnH2 C6H12 CH3(CH2)3CH=CH2 Alkynes CnH2n-2 C3H4 CH3C{CH Haloalkanes CnH2n+1X C3H7 Br CH3CH2CH2Br
Alcohols CnH2n+2 O C3H7 OH CH3CH2CH2OH
Aldehydes CnH2n O C4H8 O CH3CH2CH2CH=O
Ketones CnH2n O C4H8 O CH3CH2C=OCH3 Carboxylic acids CnH2n O2 C3H6 O2 CH3CH2COOH
Esters CnH2n O2 C3H6 O2 CH3COOCH3 Amine CnH2n+1NH2 C3H7 NH2 CH3CH2CH2NH2
Functional Groups and Homologous Series
Isomerism - two or more organic compounds with same molecular formula but different arrangements of atoms in space within the molecules.
Two main types Structural or constitutional isomerism Stereoisomerism
Isomerism in Organic Molecules
See page 77 - 81
Isomerism
Constitutional
Isomerism
Chain
Isomerism Positional Isomerism
Functional Isomerism
Stereoisomerism
Geometrical Isomerism
Optical Isomerism
Isomerism in Organic Molecules
Constitutional or Structural isomerism - molecules have same molecular formulae but different structural formulae
Divided into three types
Isomerism in Organic Molecules
See page 77 - 81
41
Constitutional Isomerism
Divided into three types i) Chain isomers - different structural formulae due to
varying lengths in its carbon chains or carbon skeletons. The length of carbon chains can be altered due to branching.
n-butane (Unbranched) Isobutane
(Branched chain)
C C C C HH
H
H
H
H
H
HH
H C C C HH
HH
HH
H
CHH
H
See page 77 - 81
Isomerism in Organic Molecules
ii) Positional isomers - molecules have same carbon chain and functional groups but differ in the position of the functional group
Isomerism in Organic Molecules
C C C C BrH
H
H
H
H
H
HH
HC C C C H
H
H
H
H
Br
H
HH
HBromobutane 2-Bromobutane
See page 77 - 81
Constitutional Isomerism
iii) Functional isomers - molecules have different functional groups, hence their structural formulae are different.
Isomerism in Organic Molecules
C C C HH
H
HH
HC C C H
H
H
HH
H
O O
Propanal Propanone
See page 77 - 81
Constitutional Isomerism
Possible structural isomers of alkanes
Isomerism in Organic Molecules
Carbon Chains
Molecular Formula Possible Isomers
4 C4H10 2
5 C5H12 3
6 C6H14 5
7 C7H16 9
8 C8H18 18
9 C9H20 35
10 C10H22 75
Rotation about a bond is NOT isomerism
Isomerism in Organic Molecules
See page 77 - 81
Stereoisomerism - molecules have same molecular formulae and structural formulae but different orientation of atoms and bond in space within the molecules
Isomerism in Organic Molecules
Divided into two types Geometrical isomers have the same
molecular formula but a different orientation in space that cannot be overcome by rotation around a sigma bond
Geometric isomers occurs if the presence of a carbon-carbon double bond or a ring structure in its molecule
Double bond between two carbon atoms, the central sigma bond is sandwiches by a pi bond above and below. This pi bond prevents the rotation of the carbon atoms.
Isomerism in Organic Molecules
Geometrical isomers
Isomerism in Organic Molecules
C CH
H3C CH3
HC C
H3C
H CH3
HCis-2- butene Trans-2- butene
H3C
HH
CH3
HH
H3C
HH
H
CH3
H
Cis-1,2-dimethylcyclopropane Trans-1,2-dimethylcyclopropane
Optical isomerism is shown by an organic compound which has a chiral carbon atom in its molecules
A chiral carbon atom is a carbon atom which has four different atoms or groups of atoms attached to it.
A chiral carbon also known as an asymmetric carbon, the molecule would have a mirror image that cannot superimposed on it. A chiral molecule and its mirror image are called enantiomer
Isomerism in Organic Molecules
Optical isomerism
Isomerism in Organic Molecules
CCH3
OHC2H5 C
CH3C2H5HO HH
I I I I I I I I
Covalent bond cleavage during reaction, chemical bonds have to be broken in order that new compounds may be formed
Breaking the chemical bonds is called fission
Bond breaking or formation can be symmetrical or unsymetrical
Symmetrical bond breaking homolytic fission
Unsymmetrical bond breaking heterolytic fission
Introduction to Organic Molecules Reactions
Homolytic fission two shared electrons of the covalent bonds are split equally.
The resulting species are known as free radical
Heterolytic fission two shared electrons of the covalent bonds are remain one one of the atom
The resulting species known as carbonium ion
Introduction to Organic Molecules Reactions
A B. . A. B.+
A B. . A+ B-+ ..
Carbonium ions there are two species carbocation and carbanion
Carbocation is an organic ion which contain a carbon atom with a positive charge
Carbanion is an organic ion which contain a carbon atom with a negative charge
Introduction to Organic Molecules Reactions
CHH
HC+HH
H+ Cl-Cl
Methyl chloride Methyl carbocation
CHH
HC-HH
H+ H+H ..
Methane Methyl carbanion
Curved arrows - indicate breaking and forming of bonds
Arrowheads with a half head (fish-hook) indicate homolytic and homogenic steps (called radical processes)
Arrowheads with a complete head indicate heterolytic and heterogenic steps (called polar processes)
Introduction to Organic Molecules Reactions
Nucleophile (Nu-) - is a species (ion or molecule) which attacks electron-poor carbon atom of organic molecule, by donating electron-pair to the atom.
Nucleophiles are Lewis bases, containing lone pair of electrons
Examples: CN-, OH-, Br-, I-, OCH3-, H2O, NH3, CH3NH2,
Introduction to Organic Molecules Reactions
Electrophile (E+) -is a species (ion or molecule) which attacks electron-rich site of organic molecules such as double bonds.
Electrophiles are Lewis acids (either positive ions or molecules with electron-deficient atom)
Examples: HCl , H3O+, AlCl3, BF3, Cl2, Br2,FeCl3, ZnCl2
Introduction to Organic Molecules Reactions
Mechanism - describes the steps behind the changes that we can observe
Reactions occur in defined steps that lead from reactant to product
We classify the types of steps in a sequence A step involves either the formation or breaking
of a covalent bond Steps can occur in individually or in
combination with other steps When several steps occur at the same time they
are said to be concerted
Introduction to Organic Molecules Reactions
Main types of reactions Addition Electrophile or Nucleophile
reactions Elimination reactions Substitution Nucleophilic Substitution Rearrangement reaction
Introduction to Organic Molecules Reactions
Addition Electrophile or Nucleophile reactions two reactants added together to form a single product
Elimination reactions single reactant splits into two products
Introduction to Organic Molecules Reactions
C C + X Y C CX Y
C O + Nu- CNu
OH
Electrophilic addition Nucleophilic addition
C CX Y
C C + X Y
Substitution or Nucleophilic substitution reactions two molecules/atoms exchange parts
Rearrangement reactions a molecule undergoes changes in the way its atoms are connected
Introduction to Organic Molecules Reactions
C CY
+ Nu- C CNu
+ Y
C C CCC C CC
Checkpoint 1
OO
HOO
CH3 OHCH3
O O
CH3
H3C
CH5C6
O C CH3O
CNCH5C6
OO C6H5
OHHO
CO
H3C
Circle the functional groups present in this molecule
Checkpoint 2 Draw the skeletal structure for each of the following compound
C
CC
C
CC
H
H
H H
H
H
H
H
H
OH
H3CCH
CH
CH3
C
OH
N C
CN
C
CC H
H
H
H
H
Checkpoint 3 1. Draw all chain isomers with a molecular formula C7H16 2. Draw the functional groups isomer for the following compounds a) CH3CH2CH2CH=CH2 b) CH3CH2COOH 3. Draw the positional isomer for the following
compounds a) CH3CH(OH)CH2CH2CH3 b) 1,2- Diethylcyclohexane
Checkpoint 4 1. Draw the stereoisomer for the following
compounds a) CH3CH2CBr=CHCH3 and b) 1,4 Dichloropentane 2. Which of the following compounds exhibit
the optical active? Draw the diagram to show the optical isomer that may exist for the particular compound.
a) (CH3)2C(NH2)(COOH) b) CH3BrCHOH