chapter 4 introduction of organic

8/6/2019 Chapter 4 Introduction of Organic

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CHAPTER 11 :

INTRODUCTIONTO

ORGANIC CHEMISTRY


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CHAPTER 11 :CHAPTER 11 :

INTRODUCTION TOINTRODUCTION TOORGANIC CHEMISTRYORGANIC CHEMISTRY

11.1 Introduction

11.2 Empirical molecular and structural formulas

11.3 Functional groups and homologous series

11.4 Classification of carbon atoms in organic molecules

11.5 Isomerism

11.6 Reactions in organic compound


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11.1 INTRODUCTION

Organic chemistry is the study ofcarbon compounds

Generally, the components of organic compound are :

C, H, O, N, S, X (halogen) and P

Carbon compounds constitute the central chemicals of

all things on this planet. Carbon compounds include

deoxyribonuicleic acids (DNAs) the giant molecules

that contain the genetic information for all living species


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Organic and Inorganic Compound

Organic compound Inorganic compound

were defined as

compounds that

could be obtained

from living

organisms

were those that

came from

nonliving sources


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Examples of organic compounds :-

CH4

methane

(a component of natural gas)

OCOCH3

COOH

CH3 CHCOOH

NH2

Methyl salicylic acid

(aspirin-a drug)

alanine

(amino acid-a protein component)

NCH3

CO2CH3

OCO

cocaine

(a pain killer)


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CH2 C

O

NH

O

S

N

COOH

penicillin (an antibiotic)

Cl CH Cl

CCl3

dichlorodiphenyltrichloroetane(DDT- a pesticide component)


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N OHN

4-hydroxyphenylazobenzene(a kind of dye)

Caffeine(found in coffee and tea)

N

N

O

CH3

C H3

N

N

C H3

O


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C NH2NH2

O

Urea(a component in urine,

also used as fertilizer)

Deoxyribonucleic acid (DNA)(carries genetic informationof living organisms)


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11.2 EMPIRICAL, MOLECULAR AND

STRUCTURAL FORMULAE

Empirical formula is the formula that shows the

simplest ratio of number ofelements present in a

molecule

Molecular formula is a formula that shows the

actual number ofatoms of each element in a

molecule. Example : C2H4 , C2H4O2


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Molecular formula = (empirical formula)n

where n is a whole number

therefore,

massformulaempiricalmassmolecularrelative

n =


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Example 1 :

If the relative molecular mass of a substance with empiricalformula CH2O is 60.0, what is the molecular formula of the

substance?

Solution :-

massformulaempiricalmassmolecularrelative

n =

0.160.20.12

0.60

= = 2

Molecular ormula = (empirical ormula)n

= (CH2

)2

= C2H

4

O2


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A sample of hydrocarbon contains 85.7 % carbon and

14.3 % hydrogen by mass. Its molar mass is 56.

Determine the empirical formula and molecular formula

of the compound.

Example 2 :


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Solution :-

Element C H

Mass (g) 85.7 14.3

Moles (n) 85.7

12.0

14.3

1.0

Smallest ratio 7.1427.142

= 1

14.437.142

= 2

= 7.142 = 14.3

@ Empirical formula = CH2n (empirical molar mass)= molar massn ( 12 x 1 + 1 x 2 ) = 56

n = 4Molecular formula = C4H8


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Structural formula is a formula that shows

how the atoms of a molecule are bonded to

one another

Representation of structural formula :-

a) CondensedStructure

b) ExpandedStructure

c) SkeletalStructure

d) 3-Dimensional formula

e) Ficher Projection


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The structural theory of organic chemistry

Two central premises are fundamental :

1.The atoms of the elements in organic compoundscan form a fixed number of bonds. The measureof this ability is called valence.

Carbon tetravalent (C atoms form 4 bonds)

Oxygen divalent

Hydrogen & halogens monovalent

C

Carbon atoms aretetrahedral

O

Oxygen atoms aredivalent

H Cl

Hydrogen and halogenatoms are monovalent


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2.A carbon atom can use one or more of itsvalences to form bonds to other carbon atoms

Carbon-carbon bonds

C C

Single bond

C C

Double bond

C C

Triple bond


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a) Condensed Structure

In condensed formulae all the hydrogen atoms

that are attached to a particular carbon are

usually written immediately after that carbon

In fully condensed formulae all atoms that are

attached to a carbon are written immediately

after that carbon


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Example :

C4H9ClCH3CHCH2CH3 or CH3CH(Cl)CH2CH3

Condensed structure

Cl


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b) Expanded Structure

Expanded structures indicate the way in which

the atoms are attached to each other and are not

representations of the actual shapes of the

molecules.

Example :

C4H9ClC C C C

H H

H H HCl

H H H H

Expanded structure


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c) Skeletal Structure

This structure shows only the carbon skeleton

The hydrogen atoms that are assumed to bepresent, are not written.

Other atoms such as O, Cl, N and etc. are shown

Example :

CH3CH(Cl)CH2CH3

Cl

=1.


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H2C CH 2

H2C CH 2

2.

=

CH2=CHCH2OH3. =OH


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Practice Exercise :

Rewrite each of the following structures using skeletalformula :-

O

CH3CH

2CH

2C CH

3

(CH3)

2CHCH

2CH

2CH(CH

3)CH

2CH

3

CH2= CHCH2CH2CH = CHCH3

O

CH3CH

2CH ( CH

3) CH

2C OH

1.

2.

3.

4.


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d) 3 - Dimensional formula(wedge - dashed wedge - wedge)

Describes how the atoms of a molecule are arrangedin space

Example :

C

Br

H

H

H(Bromoethane)

C

Br

H

H

H

C

H

BrH

H

C

H

H

B rH

Indication :-

bonds that lie in theplane of the pagebonds that lie behindthe plane

bonds that project out

of the plane of thepaper

OR OR


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e) Fischer Projection

Vertical lines represent bonds that project behindthe plane of paper

Horizontal lines represent bonds that project out of

the plane of paper

The intersection of vertical and horizontal linesrepresent a carbon atom, that is stereocentre


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Example :

2 butanol , CH3CH(OH)CH2CH3

CH3

HO

CH2

CH3

H

CH3

H

CH2

CH3

OHOR


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11.3 FUNCTIONAL GROUPS AND

HOMOLOGOUS SERIES

A functional group is an atom or group of

atoms in an organic molecule which characterizedthe molecule and enables the molecule to react

in specific ways (determines its chemical properties)


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Functional groups are important for three reasons :

1. They are the units by which we divide organiccompounds into classes

2.They are sites of chemical reaction; a particularfunctional group, in whatever compound it is found,undergoes the same types of chemical reactions

3.Functional groups serve as a basic for namingorganic compounds


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Homologous series is series of compoundswhere each member differs from the next member

by a constant CH2 unit (14 mass unit)

Members of a homologous series are calledhomologs

A homologous series has four features:

1. All the members of a particular homologous serieshave the same general formula.

Example : General formula of alcohol is CnH2n+1OH,where n=1, 2, 3 etc

For n=1 CH3OH (methanol)

For n=2 C2H5OH (ethanol)


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2. All the members of a particular homologous serieshave the same functional group. Thus, they have

the same chemical reactions and can be made bythe same general methods

Example : All alcohols contain OH group

they react with carboxylic acids to give esters

they can be prepared, for instance, by heatingdilute sodium hydroxide solution with an

appropriate alkyl halide


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3. The successive members of any homologous seriesdiffer by CH2

Example : For alcohol group.

The first few alcohols are :

CH3OH (methanol)

CH3CH2OH (ethanol)

CH3CH

2CH

2OH (propanol)

} The different by CH2} The different by CH2


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4. There is a trend in the physical properties of themembers of any homologous series.

As the molecules increase in size, there is agradual change in physical properties, e.g. theirboiling points increase


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Some important functional groups in organiccompounds :-

HomologousHomologous

SeriesSeries

FunctionalFunctional

GroupGroup

GeneralGeneral

FormulaFormula

IUPACIUPAC

nomenclaturenomenclature

PrefixPrefix-- --suffixsuffix

ExampleExample

alkanealkane nonenone CCnnHH2n+22n+2 --aneane CHCH44

methanemethane

alkenealkene C = CC = C

(double(double

bond)bond)

CCnnHH2n2n --eneene CHCH22=CH=CH22

etheneethene

alkynesalkynes CC || CC

(triple(triple

bond)bond)

CCnnHH2n2n--22 --yneyne CHCH || CHCH

ethyneethyne


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SeriesSeries


GroupGroup

GeneralGeneral

FormulaFormula

IUPACIUPAC



ExampleExample

arenearene CCnnHH2n2n--66 --benzenebenzene

alcoholalcohol OHOH

(hydroxyl)(hydroxyl)

CCnnHH2n+12n+1OHOH alkanolalkanol CHCH33CHCH22OHOH

ethanolethanol

etherether OROR(alkoxy)(alkoxy)

CCnnHH2n+22n+2OO alkoxyalkanealkoxyalkane CHCH33OCHOCH33methoxymethanemethoxymethane

haloalkanehaloalkane XX

(halogen)(halogen)

CCnnHH2n+12n+1XX haloalkanehaloalkane CHCH33CHCH22ClCl

chloroethanechloroethane

aromatic

ring

CH3

methylbenzene


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SeriesSeries


GroupGroup

GeneralGeneral

FormulaFormula

IUPACIUPAC



ExampleExample

aldehydealdehyde CCnnHH2n2nOO alkanalalkanal CHCH33C=OC=O

ketoneketone CCnnHH2n2nOO alkanonealkanone CHCH33C=OC=O

carboxyliccarboxylicacidacid

CnHCnH2n2nOO22 alkanoic acidalkanoic acid CHCH33C=OC=O

C

O

H

carbonylH

ethanal

C

O

carbonylCH3

propanone

C OH

O

carboxyl

OHethanoic

acid


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SeriesSeries


GroupGroup

GeneralGeneral

FormulaFormula

IUPACIUPAC



ExampleExample

acylacyl

chloridechloride

CCnnHH2n+12n+1

COClCOCl

alkanoylalkanoyl

chloridechloride

CHCH33C=OC=O

esterester CCnnHH2n2nOO22 alkylalkyl

alkanoatealkanoate

CHCH33COOCHCOOCH33

amideamide CCnnHH2n+12n+1

CONHCONH22

--amideamide CHCH33CONHCONH22

amineamine --NHNH22 CCnnHH2n+12n+1

NHNH22

--amineamine CHCH33NHNH22

C

O

Cl

acylCl

ethanoyl

chloride

C

O

O C

ester

C

O

NH2

ethyl

ethanoate

amideethanamide

amino methanamine


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11.4 CLASSIFICATION OF CARBON ANDHYDROGEN ATOMS IN ORGANIC

MOLECULES

Carbon atom classified primary (1o)

secondary (2o)

tertiary (3o)

quarternary (4o)

depending on the

number of carbonatoms bonded to it


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A primary carbon directly bonded to one other

carbon atom(has 1 adjacent carbon atom)

C

H

H

CH3

H

Example :

1o carbon

1oH


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A secondary carbon directly bonded to two other

carbon atoms(has 2 adjacent carbon atoms)

C

H

CH3

H CH3

Example :

2o carbon

2o H


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A tertiary carbon directly bonded to three other


C

CH3

CH3

H CH3

Example :

3o carbon

3o H


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A quarternary carbon directly bonded to four other


CCH3

CH3

CH3

CH3

Example :

4o carbon


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Similarly, a hydrogen atom is also classified as

primary, secondary or tertiary depending on the

type of carbon to which it is bonded.

1 hydrogen atom bonded to a 1 C atom




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Classification of haloalkanes (alkyl halides)

Alkyl halides are classified based on the carbon atom

to which the halogen is directly attached.

1 alkyl halide the halogen atom is bonded to a

primary carbon atom

2 alkyl halide the halogen atom is bonded to asecondary carbon atom

3 alkyl halide the halogen atom is bonded to atertiary carbon atom


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H C

H

H

C

H

H

Cl

H C

H

H

C

H

C

H

H

HCl

H C

H

H

C C

H

H

HCl

CH3

1 alkyl chloride

1 C

2 alkyl chloride

2 C

3 alkyl chloride

3 C


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Classification of alcohols

Alcohols are classified based on the carbon atom

to which the hydroxyl group is directly attached.

1 alcohol the hydroxyl group is attached to a

1 carbon atom

2 alcohol the hydroxyl group is attached to a2 carbon atom

3 alcohol the hydroxyl group is attached to a3 carbon atom


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H C

H

H

C

H

H

OH

H C

H

H

C

H

C

H

H

HOH

H C

H

H

C C

H

H

HOH

CH3

1 alcohol

1 C

2 C

2 alcohol

3 alcohol

3 C


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Classification of amines

Amines are classified based on the number of alkylgroups or carbon atoms that are directly attached

to the nitrogen atom

1 amine N is bonded to one alkyl group

2 amine N is bonded to two alkyl groups

3

amine N is bonded to three alkyl groups


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H3

C N

H

H

H3

C N H

CH3

H3C N

CH3

CH3

N bonded toone alkyl group

A primary (1)amine

N bonded totwo alkyl group

A secondary (2)amine

N bonded to three

alkyl group

A tertiary (3)amine


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ISOMERISM

Structural/Constitutional Isomerism Stereoisomerism

Isomerism

Chainisomerism

Positionalisomerism

Functionalgroup

isomerism

Geometricisomerism

Opticalisomerism


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Isomerism is the existence of different compounds

with the same molecular formula but different

structural formulae

Isomers different compounds that have same

molecular formula

Two types ofisomerism

structural isomerism

stereoisomerism

different order of attachmentof atoms

different spatial arrangement of

atoms in molecules


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Structural isomerism

Chain/skeletal

isomerism

Structural isomers are different compounds with

the same molecular formula but differ in the order

of attachment of atoms

Positional

isomerism

Functional

groupisomerism


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The isomers differ in the carbon skeleton(different carbon chain)

a) Chain/skeletal isomerism

They possess the same functional group andbelong to the same homologous series

Example :

C5H12 :

CH3CH2CH2CH2CH3

CH3CHCH2CH3

CH3

CH3-C-CH3

CH3

CH3


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1,2-dimethylbenzene

iii) C8H10 CH3CH3

CH3

CH3

1,3-dimethylbenzene

CH3

CH3

1,4-dimethylbenzene


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c) Functional group isomerism

These isomers have different functional groups

and belong to different homologous series withthe same general formula

Different classes of compounds that exhibit

functional group isomerism :-

General formulaGeneral formula Classes of compoundsClasses of compounds

CnH2n+2O alcohol and ether

CnH2nO aldehyde and ketone

CnH2n alkene and cycloalkane

CnH2nO2 carboxylic acid and ester


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Example :

i) C2H6O CH3CH2OH

ethanol

CH3OCH3

dimethyl ether

ii) C3H6O CH3CH2C-H

O

propanal

CH3C-CH3

O

propanone

iii) C3H6O2 CH3CH2C-OH

O

propanoic acid

CH3C-O-CH3

O

methyl ethanoate


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Stereoisomerism

Geometric Isomerism Optical Isomerism

a) Geometric isomerism

occurs only in two classes of compounds :

Alkenes & cyclic compound

(because of rigidity in molecules)


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Geometric isomers (also called cis-trans isomers)

are stereoisomers that differ by groups being

on the same side (cis-isomer) or opposite

sides (trans-isomer) of a site of rigidity in a molecule

The requirements for geometric isomerism :

i) restricted rotation about a C=C,double bond, inalkenes or a C-C single bond in cyclic compounds

ii) each carbon atom of a site of restricted rotation hastwo different groups attached to it


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Examples :

H3C CH3

H H

C C=

i)

cis-2-butene

H3C

C=C

CH3

H

H

trans-2-butene

ii) H3C CH2CH3

C= C

H CH3

trans-3-methyl-2-pentene

H3C CH3

C= CH CH2CH3

cis-3-methyl-2-pentene


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iii)

HH

CH3 CH3

cis-1,2-dimethylcyclohexane

H

HCH3

CH3

trans-1,2-dimethylcyclohexane

Cl

Cl

H

H

iv)

Cl

Cl

H

H

cis-1,3-dichlorocyclopentane trans-1,3-dichlorocyclopentane


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If one of the doubly bonded carbons has 2 identical

groups, geometric isomerism is not possible.

Examples :

CH3CH2i)

C = C

H

HH3C

2-methyl-2-butene

Hii)

C= C

CH3

CH3Cl

1-chloro-2-methylpropene


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cis-trans isomers have similar chemical properties

but different physical properties

They differ in melting and boiling points and

solubility due to different polarity of the molecules

cis-isomers polar molecules

trans-isomers non-polar

Melting point: trans- isomer > cis-isomer Boiling point: cis-isomer > trans- isomer

Stability: trans-isomer > cis-isomer


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b) Optical isomerism

If a beam of light is passed through a piece of

polarizer prism, the emergent light vibrates in a

single plane, hence it is called aplane-polarized

light

Opticallyactive compounds have the ability to

rotate plane-polarized light

The angle of rotation can be measured with an

instrument called polarimeter


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Schematic representation of a polarimeter containingan optically active sample :

clockwise rotation plus sign (+) / dextrorotarory

anticlockwise rotation minus sign (-) / levorotorary


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The requirements for optical isomerism :-

i) molecule contains a chiral carbon or chiral centre(carbon atom with 4 different groups attached to it)

ii) molecule is not superimposable with its mirror image

A representation of a chiral molecule with

3-dimensional formula :-

P

CQ

R

S* P{Q{R{S

*designates chiral centre


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Enantiomers are apair of mirror-image molecules

that are notsuperimposable (must have one or more

chiral carbons)

Examples :

i) 2-butanol, CH3CHCH2CH3

OH

C*

CH2CH3

H3C

OHH

C

CH2CH3

CH3HOH

enantiomers

:-


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A racemic mixture or racemate is an equimolar

mixture of enantiomers which is optically inactive

because the two components rotate plane-polarized

light equally (same degree of rotation but in opposite

direction so they can cancel each others rotation)

A pair of enantiomers have identical chemical and

physical properties but differ in the direction of

rotation of plane-polarized light


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A compound with n chiral centers can have a

maximum of2n stereoisomers

If a molecule contains two or more chiral centers,

diastereomers may exist

Diastereomers are stereoisomers that are not

mirror images of each other

All physical properties of diastereomers are usually

different from one another

Example :


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Example :

The 4 stereoisomers of 2-amino-3-hydroxybutanoicacid CH3CH-CHCOOH are shown below using

OH NH2Fischer projection formula:-

COOH COOH

CH3 CH3

HH

HH

NH2 H2NOH HO

enantiomers

COOH

NH2H

H

HO

CH3

COOH

H

H

OH

H2N

enantiomers

CH3

A B

C D

Four pairs ofdiastereomersare identified :

A and C;A and D ;B and C;B and D


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Meso compoundis a stereoisomer that has more

than one chiral centres and that issuperimposableon its mirror image because of the presence of an

internal plane ofsymmetry, hence it is optically

inactive (does not cause a rotation of plane-polarizedlight)


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Example : Tartaric acid , HOOCCH(OH)CH(OH)COOH

COOH

OH

OH

H

H

COOH

COOH

COOH

HO

HO

H

H

COOH

COOH

H

H

OH

OH

plane of symmetry

plane of symmetry

rotate 180o

P Q

identical


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At first glance, Pand Q are assumed to be enantiomers

But if compound Q is rotated 180o in the plane ofthe paper, it is actually identical to compound P,therefore Pand Q are superimposable mirror images

Pand Q are thesame compound

It is a meso compound


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COOH

OH

OH

H

H

COOH

COOH

COOH

R S

COOH

COOH

HHO

H OH*not a plane of symmetry

*not a plane of symmetry

rotate 180o

different

H OH

HHO


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R and S are related as mirror images and are notsuperimposable even if rotated 180o

Thus R and Sconstitute an enantiomeric pair

There are 2 pairs of diastereomers :

Pand R & Pand S


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Further examples of meso compounds:

CH3

CH3

Cl

Cl

H

H

CHO

CHO

HO

HO

H

HH OH plane of symmetry


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11.6 REACTIONS OF ORGANIC COMPOUNDS

11.6.1 Types of CovalentBond Cleavage/Fission

All chemical reactions involved bond breaking andbond making

Two types of covalent bond cleavage :-

Homolytic cleavage

Heterolytic cleavage


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a) Homolytic Cleavage

Occurs in a non-polar bond involving two atoms of

similar electronegativity

A single bond breaks symmetrically into two equal

parts, leaving each atom with one unpaired electron

Free radicals are formed in homolytic cleavage

X X X + X 2X

free radicals


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b) Heterolytic Cleavage

Occurs in a polar bond involving unequal sharingof electron pair between two atoms of differentelectronegativities

A single bond breaks unsymmetrically and both the

bonding electrons are transferred to the moreelectronegative atom

Cation and anion are formed in heterolytic cleavage

A BA

-

+ B+

A is moreelectronegative

A+ + B- B is more

electronegative

cationanion

anioncation


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Carbocations and free radicals are intermediates inorganic reactions.

They are unstable and highly reactive

11 6 2 R ti I t di t


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11.6.2 Reaction Intermediates

a) Carbocation

Also called carbonium ion

A very reactive species with apositive charge

on a carbon atom

Carbocation is formed in heterolytic cleavage


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Example :

(CH3)3C ClH H

(CH3)3C+

carbocation

+ Cl-

anion

Chlorine is more electronegative than carbon andthe CCl bond is polar

The CCl bond breaks heterolitically and both thebonding electrons are transferred to chlorine atomto form anion and carbocation

b) F R di l


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b) Free Radical

A very reactive species with an unpaired electron

Formed in homolytic cleavage

Cl Cl

Example :

uv Cl

free radicals

+ Cl

C C C + C

H3C H CH3 + H

11 6 3 R l ti St biliti f


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11.6.3 Relative Stabilities ofCarbocations and Free Radicals

Carbocation and free radical primary

secondary

tertiary

depending on the number of carbon atoms directlybonded to the :-

positively charged carbon atom (for carbocation)

carbon atom with unpaired electron (for free radical)


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The stability of carbocation increases with thenumber of alkyl groups present

The alkyl groups are electron-releasing relative tohydrogen, thus help to stabilize the positive chargeon the carbocation


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Lik i h bili f f di l i


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Likewise, the stability of free radical increases asmore alkyl groups are attached to the carbon atomwith unpaired electron

Free RadicalStability :

H C H < R C H < R C H < R C R

H H RR

methylradical primary(1) secondary(2) tertiary(3)

Increasing stability

11 6 4 Reagents and Sites of Organic Reactions


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11.6.4 Reagents andSites of OrganicReactions

a) Elec trophile (E+

)

Means electron loving

An electron-deficientspecies and electron-pair

acceptorthat attacks a part of a molecule wherethe electron density is high

An electrophile can be either neutralorpositivelycharged


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Examples of electrophiles :-

1.cations such as H+, H3

O+, NO2+, Br+ etc.2.carbocations.3.Lewis acids such as AlCl3, BF3 etc.4.oxidizing agents such as Cl2, Br2 and etc

Examples of electrophilic sites in organic molecules :-

molecules with low electron density around apolar bond such as :-

H+ H- H+ H- H+ H-C = O C X C OH

carbonyl haloalkanes hydroxyl

compound


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b) Nucleophile (Nu-)

Means nucleus loving

An electron-rich species and electron-pair donorthat attacks a part of a molecule where the electron

density is low

A nucleophile can be either neutralor negativelycharged

E l f l hil


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Examples of nucleophiles :-

1. anions such as OH-

, RO-

, Cl-

, Cn-

etc.2. carbanions. (species with ve charge on C atoms)3. Lewis bases which can donate lone pair electrons

such as NH3, H2O etc.

Examples of nucleophilic sites in organic molecules :-

molecules with high electron densityaround thecarbon-carbon multiple bond such as :-

-C=C- (alkenes) , -C|C-(alkynes),

(benzene ring) and etc.

11 6 5 T f O i R ti


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11.6.5 Types of OrganicReactions

The four main types of organic reactions are:

Addition

Substitution

Elimination

Rearrangement


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a) ElectrophilicAddition

Initiated by an electrophile, which attacks anucleophilic site of a molecule

Typical reaction of unsaturated compounds suchas alkenes and alkynes

Example :

CH3

CH=CH2

+ Br2

CH3

CHBrCH2

Brroom

temperature

electrophile

b) l hili ddi i


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b) NucleophilicAddition

Initiated by a nucleophile, which attacks anelectrophilic site of a molecule

Typical reaction ofcarbonyl compounds

Example :

CH3 C CH 3 + HCN

O

CH3 C CH3

OH

CN

H

H+

H+ CN-


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2. Substitution Reaction

A reaction in which an atom orgroup in a molecule is replacedby

another atom or group

a) Free-radicalSubstitution

b) ElectrophilicSubstitution

c) NucleophilicSubstitution

) F di l S b tit ti


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a) Free-radicalSubstitution

Substitution which involves free radicals asintermediate species

Example :

CH3CH3 + Cl2 CH3CH2Cl + HCluv light


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b) ElectrophilicSubstitution

Typical reaction ofaromatic compounds

The aromatic nucleus has high electron density,thus it is nucleophilic and is tend to electrophilic

attack

Example :

+ Br2Fe

catalystBr + HBr

electrophile

BrH

BrH


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c) NucleophilicSubstitution

Typical reaction of saturated organic compoundsbearing polar bond as functional group, such ashaloalkane and alchohol

Example :

CH3CH2Br + OH-(aq) CH3CH2OH + Br

-(aq)

nucleophile

HH


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3. Elimination Reaction

A reaction in which atoms or groups are removedfrom adjacent carbon atoms of a molecule to forma multiple bond(double or triple bond)

E

limination reaction results in the formation ofunsaturated molecules

CH3CH2OH CH2= CH2 + H2OConc. H2SO4

(

Example :


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chapter 4 introduction of organic

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