Preview organic chemistry for the JEE mains and advanced vol II by i s s raju

Organic Chemistry
for the
JEE Main and Advanced
Volume II

I.S.S. Raju


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ISBN 978-93-325-7562-2
eISBN 978-93-325-8663-5
First Impression
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Contents
Preface  v
Acknowledgment 
About the Author 

vii

ix

Chapter 1

Halogen Derivatives of Hydrocarbons or Halohydrocarbons

1.1–1.132

Chapter 2

Hydroxy Compounds, Ethers and Phenols

2.1–2.230

Chapter 3

Carbonyl Compounds

3.1–3.160

Chapter 4

Carboxylic Acids

4.1–4.88

Chapter 5

Acid Derivatives

5.1–5.80

Chapter 6

Compounds Containing Nitrogen

Chapter 7

Carbohydrates

7.1–7.72

Chapter 8

Amino Acids and Proteins

8.1–8.32

Chapter 9

Polymers

9.1–9.40

Chapter 10

Practical Organic Chemistry

6.1–6.134

10.1–10.28


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Preface
Organic Chemistry is one of the most fascinating subjects as it deals with the chemicals related to living organisms. The
subject has grown to such a level that it is not easy for any person to go through it completely. The number of organic
compounds known has gone to almost 15 million in the past few years. It is further increasing every year. Understanding
organic chemistry becomes difficult due to this reason. In the past few years, its presentation also changed in some cases
due to this recent finding, but still there are some ambiguities.
Writing a book of Organic Chemistry for students at the 10+2 level is a challenge as there are no boundaries for it.
At this level, students have no practical experience. Their requirements should be addressed by good books, effectively
guided by an able teacher. Organic Chemistry has to be presented to such students with crystal clear explanations covering
all concepts, while ensuring that the discussion does not digress to topics beyond the scope of 10+2 level.
The first volume of Organic Chemistry was published conforming to this requirement.
This second volume of Organic Chemistry adheres to the style followed in the first volume in its delineation of
reaction mechanisms and named reactions. An effort has been made to keep the explanations simple to enable students
understand and apply the concepts effectively to solve questions in IIT entrance examination. Questions framed in the book
have been modeled on the syllabus of CBSE and NCERT for the same purpose.
Any error noticed in the book may please be brought to my notice so that it can be rectified in the subsequent editions.
Suggestions for the book’s improvement are welcome.

I.S.S. Raju


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Acknowledgment
I thank my family members and friends who encouraged me to write this book at the age of 73. My family members were
unfailingly supportive and encouraging during the long months I spent glued into many relevant resources while writing
this book.
I am especially thankful to my great granddaughter Chy Akshara who plays with me all the time, for not disturbing
me at the time of writing the manuscript.
I am obliged to Pearson India Education Services Pvt. Ltd. for publishing this book. In particular, I am grateful to
their editors Sri Abhilash Ayyappan and Mrs G. Sharmilee whose sincere efforts helped in bringing out this book in record
time.
I.S.S. Raju


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About the Author
I.S.S. Raju retired as Principal, with 35 years of experience in teaching graduate and post
graduate students the subject of organic chemistry. He currently coaches JEE Main and
Advanced aspirants, a vocation that he has been actively pursuing since his retirement 15 years
ago.
His rich experience in this subject has assisted many students in gaining better command
over this subject as well as helping them do well academically. His approach in assisting
students is methodical and lucid. This helps students immensely, especially when it is about
understanding the various complex theories and concepts of organic chemistry.
The author’s tenure as a principal and his post-retirement contributions, in tirelessly
coaching IIT aspirants, has brought him into the crux of celebrating the golden jubilee of his
academic career.


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Halogen Derivatives
of Hydrocarbons or
Halohydrocarbons

1

1.1 Organic Compounds
Organic compounds formed by the displacement of one or more hydrogen atoms of a hydrocarbon
by halogen atoms are halogen derivatives or halohydrocarbons. Hydrocarbons from which they are
formed may be aliphatic or aromatic, saturated or unsaturated. Accordingly they are classified as shown
below:

1.1.1 Aliphatic Saturated Monohalogen Derivatives
These are formed by the displacement of only one hydrogen atom of an alkane by a halogen atom.
They are called alkyl halides or haloalkanes. Their general formula is CnH2n + 1 X. They are
generally represented as RX, where R is any alkyl group, and X is any halogen atom.
1.CH3Cl methyl chloride or halomethane.
2.CH3CH2Br or C2H5Br ethyl bromide or bromoethane
3. CH3 CH 2 CH 2 n-propyl chloride or 1-chloropropane
|
Cl



1.2  ■  Chapter 1
4. CH3 − CH − CH3 iso propyl chloride or 2-chloropropane
|
Cl

  (3) and (4) are position isomers.
5. CH3 CH 2 CH 2 CH 2 n butyl chloride or 1-chlorobutane.
|
Cl


6. CH3 − CH − CH 2 − CH3 secondary butyl chloride or 2-chlorobutane.
|
Cl

  It is optically active, C2 is asymmetric.

CH3
|
7. CH3 − CH− CH 2 isobutyl chloride or 1-chloro-2-methyl propane.
|
Cl



CH3
|
8. CH3 − C−CH3 tertiary butyl chloride or 2-chloro-2-methyl propane.
|
Cl


  (5) and (6) are position isomers. (5) and (7) are chain isomers, (6) and (8) are chain isomers,
(7) and (8) are position isomers.

  These alkyl halides are classified as: (a) primary, (b) secondary, and (c) tertiary alkyl halides
based on the nature of carbon atom to which halogen atom is connected.


(a)Primary carbon: It is that, which is connected to only one more carbon. If halogen is
connected to any primary carbon, that is primary alkyl halide. Alternatively if the carbon
holding the halogen atom is connected to two H-atoms, that is primary alkyl halide. General
°
formula is R− CH 2 denoted as 1.
|
X
  In the alkyl halides shown above—(1), (2), (3), (5), and (7) are primary alkyl halides.

(b)Secondary carbon: It is that, which is connected to two other carbon atoms. If halogen
is connected to a secondary carbon holding only one H-atom that is a secondary halogen
°
derivative or alkyl halide. General formula R− CH− R1 denoted as 2.
|
X
  (4) and (6) are secondary alkyl halides.

(c)Tertiary carbon: It is connected to three other carbon atoms. If halogen atom is connected
to tertiary carbon, that is tertiary alkyl halide. It does not have a H-atom on the carbon
R′
|
°3. General formula R− C− R ′′.
holding halogen. It is denoted as
|
X
  (8) is tertiary alkyl halide.

1.1.2  Dihalogen Derivatives
If two hydrogen atoms of a hydrocarbon are displaced by two halogen atoms, the compound formed is
dihalogen derivative. General formula CnH2nX2.


Halogen Derivatives of Hydrocarbons  ■ 1.3
These are classified into three types:


1.Gem dihalogen derivatives: If both the halogen atoms are connected to the same carbon, they
are geminal dihalogen derivatives or dihaloalkanes-idene is suffixed to the name of alkyl group in
writing their names.





(a)CH2Cl2 methylidene chloride or 1, 1-dichloromethane.
(b)CH3–CHCl2 ethylidene chloride or 1, 1-dichloroethane.
(c)CH3CH2CHCl2 propylidene chloride or 1, 1-dichloropropane.
Cl
|

(d)CH3 − C−CH3 isopropylidene chloride or 2, 2-dichloropropane.
|
Cl
  (c) and (d) are position isomers.

2.Vicinal dihalogen derivatives: If two halogen atoms are present on adjacent carbon atoms—they
are vicinal dihalogen derivatives. They are named as addition product of corresponding alkene.
CH 2 − CH 2 1, 2-dichloroethane or ethylene chloride.
|
|
Cl
Cl

CH3 − CH− CH 2 1, 2-dichloropropane or propylene chloride.
|
|
Cl Cl

3.Isolated dihalogen derivatives: If halogen atoms scatter in the carbon skeleton, they are isolated
halogen derivatives. If they are on terminal carbon atoms, they are also called polymethylene
halides.
CH1− CH 2 − CH 2 1, 3-dichloropropane or trimethylene chloride.
|
|
Cl
Cl
CH3 − CH − CH 2 − CH 2 1, 3-dichlorobutane.
|
|
Cl
Cl

Gem dihalogen derivatives and vicinal dihalogen derivatives are position isomers.

1.1.3 Trihalogen Derivatives
If three H-atoms are displaced by three halogen atoms, they are trihalogen derivatives. General formula
is CnH2n–1X3. Among them those which are having the three halogen atoms on the same carbon are
important.
CHCl3 chloroform, trichloromethane
CHBr3 bromoform, tribromo methane
CHI3 iodoform, triiodomethane.
CH 2 − CH − CH 2 1, 2, 3-tribromopropane
|
|
|
Br Br Br
CH− CH −CHBr2 1, 1, 2-tribromopropane.
|
Br

1.1.4 Tetrahalogen Derivatives
If 4 H-atoms are displaced by 4 halogen atoms—they are tetrahalogen derivatives. CnH2n–2X4
CCl4—carbon tetrachloride or tetrachloromethane.


1.4  ■  Chapter 1
1.1.5 Polyhalogen Derivatives
Polyhalogen derivatives contain more than 4 halogen atoms in the place of H-atoms in a hydrocarbon
C2Cl6 hexachloroethane.
In the place of Cl if Br is introduced in example given above—they are named as bromides or
bromoalkanes. Same is the case with iodo derivatives.

1.1.6 Unsaturated Halogen Derivatives
They are named as derivatives of alkenes or alkynes. They are haloalkenes or halo alkynes (alkenyl halides

or alkynyl halides).
These are classified into two categories:


1.Vinyl type: These have halogen connected to a doubly bonded carbon.
CH 2 = CH vinyl chloride chloroethene
|
Cl
CH3 − CH = CH 1-chloropropene
|
Cl
CH3 − C = CH 2 2-chloropropene
|
Cl
CH3–C ≡ C–Cl 1-chloropropyne

  The doubly bonded carbon to which X is connected is called vinylic carbon.
2.Allyl type: In these compounds—the halogen is connected to a saturated carbon of alkene (which
is connected to doubly bonded carbon). The saturated carbon connected to doubly bonded carbon
is allyl carbon.
Allyl carbon CH 2 − CH = CH 2 allyl chloride or 3-chloropropane
|
Cl
CH3 − CH − CH = CH − CH3 4-bromobut-2-ene
|
Br
CH 2 − C ≡ CH 3-bromopropyne.
|
Br

1.1.7 Nomenclature of Aliphatic Halogen Derivatives
1.The longest continuous carbon chain containing halogen atom is selected as parent chain. If a
double or triple bond is present—the parent chain should have both double or triple bond as well
as halogen atom as far as possible. But double or triple bond takes priority over halogen atom as it
is considered as a substituent as far as naming is concerned.
2.The carbon atoms of the parent chain are allotted serial numbers from left to right or right to left
in such a manner that the carbon holding the halogen gets lowest serial number if the molecule is
saturated.
  If there is a double or triple bond, priority given to the double or triple bond while allotting serial
numbers.
3.An appropriate word root is written depending on the number of carbon atoms present in the parent
chain.
4.A primary suffix like ane, ene or yne is included depending on the nature of C–C bonds in the
parent chain.


Halogen Derivatives of Hydrocarbons  ■ 1.5






5.The names of halogen atoms present in the molecule are prefixed before word root in alphabetical
order.
6.Numerical prefixes like di, tri are used if two or more number of halogen atoms are present. Their
positions in the parent chain are shown in front of their names.
7.The serial number of the carbon atom holding two or more same halogen atom is repeated twice,
thrice like that.
8.Names and numbers are separated by hyphens, numbers are separated by commas.

9. If alkyl groups are also present as substituents, their names are also prefixed to word root along with
the serial number of the carbon atom to which they are connected in the parent chain in alphabetical
order.

Examples CH3 − CH 2 − CH− CH 2 CH3 3-chloromethyl pentane.
|
CH
2 Cl
 
Here –CH2Cl is considered as a substituent as the other chain has more number of carbon atoms
3

2

1

CH 2 − CH = CH 2 3-chloro propene
|
Cl
Priority is given to double bond in allotting serial numbers.
CH3
|
1
2
CH3 CH − CH− CH3 2-bromo-3-methylbutane.
3
4
|
Br
CH3 CH − CH = CH − CH3 4-bromopent-2-ene.

|
Br

1.1.8 Aromatic Halogen Derivatives
These are classified into two types: (1) Nuclear substituted halogen derivatives, and (2) Side chain
substituted halogen derivatives.

1.1.8.1 Nuclear Substituted Halogen Derivatives
These are compounds in which halogen atom is connected to a carbon atom of the benzene ring. These
are haloarenes or aryl halides.


1.6  ■  Chapter 1
1.1.8.2 Side Chain Substituted Halogen Derivatives
They are aralkyl halides. Halogen atom is present in the side chain

1.2 Isomerism
1.2.1 Chain Isomers
Two or more alkyl halides having the same formula, however differing in the arrangement of carbon
atoms in the parent chain, without a difference in the position of X are chain isomers.

These two differ only in the carbon skeleton. They are chain isomers.

No difference in the position of halogen atom in both.

1.2.2 Position Isomers
Two or more alkyl or aryl halides having the same formula differ only in the position of the halogen atom
(without any difference in the carbon skeleton), they are position isomers.
1.

are position isomers.



Halogen Derivatives of Hydrocarbons  ■ 1.7
2.


all the four are position isomers 1, 3-dichloropropane including stereo-isomers, these are 5.
all the three are position isomers.

3.


these 4 are position isomers.



1.2.3 Ring-chain Isomerism
An unsaturate halogen derivative and a cycloalkyl halide are ring chain isomers.

Chlorocyclopropane and allyl chloride—both have the same formula C3H5Cl, but one has open chain
structure and the other has ring structure.

1.2.4 Geometrical Isomerism
If each of the two doubly bonded carbon atoms in an unsaturated halogen derivative, carries two different
atoms or groups—it exhibits geometrical isomerism. It exists in the form of two geometrical isomers.
As the double bond does not allow the C–C bond to rotate—atoms or groups connected to these doubly
bonded carbons arrange themselves around those two carbons in two different ways in space.

1.8  ■  Chapter 1
The one in which similar atoms or groups are on the same side is cis isomer. The other in which
they are on opposite side is trans isomer. These two don’t interchange as the double bond does not allow
the bond to rotate at room temperature.
They have different physical and chemical properties:
■■ cis is more polar generally and more soluble.
■■ cis has higher boiling point.
■■ trans has higher melting point and more stable.

But trans is more polar than cis isomer, in this case as positive and negative pole are separated
farther away.
Halogen derivatives of cycloalkanes also exhibit geometrical isomerism.

1.2.5 Optical Isomerism
An alkyl halide exhibits optical isomerism provided it and its mirror image do not superimpose on each
other. It is possible when it has an asymmetric carbon atom and does not have either plane of symmetry
or centre of symmetry. It should be chiral. 2-chlorobutane is optically active as C2 is asymmetric.

These two molecules have object-mirror image relationship, and don’t superimpose on each other.
One rotates plane polarised light towards right side. That is d-isomer. The other rotates it towards left side.
That is l-isomer.
Unsaturated halogen derivatives also can exhibit optical isomerism, provided they have a chiral
centre
CH3
|
CH 2 = CH− CH − CH 2 Cl exhibits optical isomerism
CH3CH = CH− CH − CH 2 Cl exhibits both geometrical and optical isomerism
|
CH3

 


Halogen Derivatives of Hydrocarbons  ■ 1.9
It exits in four stereo isomeric forms. cis and its mirror image, trans and its mirror image.

Halogen derivatives of cycloalkanes also exhibit optical isomerism.

Both cis and trans isomers of 1, 4-dichlorocyclohexane are inactive as former has plane of
symmetry, latter has centre of symmetry.
In fact both don’t have asymmetric carbon atoms.

1.2.6 Conformational Isomerism
It arises due to C–C bond rotation. When C–C bond rotates, the atoms or groups on one carbon, arrange
themselves in different positions in space around that carbon, with respect to those on adjacent carbon.
Such different forms of a molecule, with different spatial arrangement of atoms of groups around a
carbon atom, arising due to C–C bond rotation are conformers.
The angle through which the C–C bond rotates is dihedral angle. If it is 60°—1, 2 dichloroethane
exists in 6 different conformers.


1.10  ■  Chapter 1
Among these—antiform is more stable as it does not have both torsional strain and steric strain.
anti > gauche > half eclipsed > cis eclipsed
cis eclipsed has both torsional and steric strain and become least stable.
Conformers cannot be separated. They interchange at a rapid rate, as the energy required for
interchange is less, and more energy is available during collisions. The actual number of conformers is
infinite.

1.3 Preparation of Aliphatic Halogen Derivatives

1.3.1 From Alkanes
Direct halogenation of alkanes gives a mixture of alkyl halides.
X
hv

X
hv

2
2
CH 4 
→ CH3 X + HX 
→ CH 2 X 2 + HX

X
hv

X
hv

2
2

→ CH X 3 + HX 
→ CX 4 + HX

As the mixture cannot be separated so easily, this method is not used to prepare alkyl halides
generally.
Fluorination is highly explosive as it is exothermic even in dark, so fluoro compounds are not
prepared by this method.

Chlorination takes place in presence of light. Bromination takes place on heating. Iodination
requires heating in presence of a catalyst and it is reversible.

HI is a strong reducing agent and reduces the alkyl iodide formed back into alkane. To prevent
backward reaction, oxidising agents like conc. HNO3, H3PO4, HIO3 or HgO are added.
RH+I IRI+I H
5HI + HIO3 
→ 3I 2 + 3H 2 O
2HI + HNO3 
→ NO 2 + H 2 O + I 2
2HI + HgO 
→ I 2 + Hg + H 2 O
Reactivity of halogen F2 > Cl2 > Br2 > I2.
Mechanism: It is a free radical substitution and chain reaction:
1.
halogen free radicals.
It is a chain initiation reaction
2.

3.

left over after stage (3) collides with another molecule of alkane and converts it into another
alkyl free radical R⋅. Thus, stages (2) and (3) repeat successively until the alkane taken is converted to
RX. These stages are chain propagation stages.


Halogen Derivatives of Hydrocarbons  ■ 1.11
Termination reaction:
X ⋅ + ⋅ X → X 2 R ⋅ + ⋅ X → RX R ⋅ + ⋅ R → R − R.
Rate determining stage is second stage, that is formation of alkyl free radical.

R − H + Cl

∆H =+104 kcal/mole

→

R ⋅ + HCl

RH + Br ⋅

∆H =−103 kcal/mole ∆H =+1004 kcal/mole

→

R ⋅ +HBr

∆H =−88 kcal/mole

Second stage is more endothermic during bromination. Energy of activation of chlorination is
3 kcal/mole whereas for bromination it is 18 kcal/mole. Hence, chlorination takes place more easily than
bromination. Eact is, the energy required for the formation of transition state, i.e. [R ... H ... X]. As this
value increases rate of reaction decreases. Thus, reactivity is fluorination > chlorination > bromination
> iodination. Transition state collapses into R⋅ subsequently.
Selectivity: Bromine being less reactive prefers to displace those H-atoms which are easily displaced. Rates of displacement of 1°, 2° and 3° H-atoms are:
1°
2°
3°
During chlorination 1 : 3.8 : 5
During bromination 1 : 82 : 1600
Rate of displacement of a H-atom a {stability of intermediate free radical formed during its displacement}.

A tertiary free radical is more stable and so a tertiary H-atom is more easily displaced than
secondary and primary hydrogen atoms.

Halogenation (mono) of an alkane produces a number of isomers including stereoisomers.

Totally they are 6, including stereoisomers.
If the product is optically active—racemic mixture is formed.

Sulphuryl chloride and t-butoxy chloride are other reagents used for chlorination.
1.R′–O–O–R′ → 2R′O
2.



1.12  ■  Chapter 1

3.

 Cl → SO + Cl ⋅
SO
4.
2
2
5. Cl ⋅ + RH → HCl + R ⋅ stages 3, 4, 5 are propagation stages.
(C2H5)4Pb initiates chlorination even in dark at 150°C.
O2 slows down chlorination.

1.3.2 Formation of Unsaturated Halogen Derivatives
Alkenes undergo allylic substitution (in a-position) which is also a free radical substitution.

Mechanism:
1.Cl–Cl → 2 Cl

2. CH3 − CH = CH 2 + Cl⋅ → CH
2 − CH = CH 2 + HCl
Allyl free radical

 −CH = CH + Cl →CH − CH = CH + Cl
3. CH
2
2
2
2
2
|
Cl

(2) and (3) are chain propagation stages.

This is allylic rearrangement.
  The rearranged product is more stable as it has more number of a-H-atoms and stabilized by
more number of hyper conjugate resonating structures. Free radicals don’t undergo hydride or
alkyl shifts.
4.Allylic bromination is carried out with N-bromosuccinimide (NBS).
(a)




Halogen Derivatives of Hydrocarbons  ■ 1.13

(b)

(c)


  The bromine so formed should be in small quantity then substitution takes place in allyl
position. Addition takes place only when it is in larger quantity which is not possible under these
circumstances of this experiment.

1.3.3 From Alkenes and Alkynes
Alkenes undergo addition with H–X, and form alkyl halides. It is Grooves process

It is electrophilic addition. H⊕ acting as an electrophile initiates the reaction. An intermediate
carbocation is formed. It combines with X .
Rearrangements, ring expansion are common whereever possible.
If the product is optically active—a racemic mixture is formed.
Presence of electron releasing groups increase the rate of reaction. Withdrawing groups decrease
the rate of reaction.
If the alkene is unsymmetrical addition takes place via Markovnikov’s rule.


1.14  ■  Chapter 1

Alkenes give vicinal dihalogen derivatives with halogens

cis alkene gives racemic mixture if the product is optically active and transisomer gives meso
dihalogen derivative.
Alkynes give gem dihalogen derivatives with H–X

1.3.3.1  Anti Markovnikov Addition

Only addition of HBr takes place against Markovnikov rule in presence of peroxide.

Mechanism:
∆

R − O − O − R 
→ 2R − O ⋅
Peroxide

Free radicals

R − O ⋅ + HBr → R − OH + Br ⋅