Atul singhal the pearson guide to organic chemistry for the IIT JEE pearson education (2010)

General Organic Chemistry-1 Nomenclature and IsomerismMODERN DEFINITION OF ORGANIC CHEMISTRY Organic compounds may be de¿ ned as hydrocarbons and their derivatives and the study of hydro

Chandigarh x Chennai x Delhi

Atul Singhal

Organic Chemistry

for the IIT-JEE

The aim of this publication is to supply information taken from sources believed to be valid and reliable This is not an attempt to render any type of professional advice or analysis, nor is it to be treated as such While much care has been taken to ensure the veracity and currency of the information presented within, neither the publisher nor its authors bear any responsibility for any damage arising from inadvertent omissions, negligence or inaccuracies (typographical or fac-tual) that may have found their way into this book.

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To my grandparents,

parents and teachers

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(Nomenclature and Isomerism)

C

(Haloalkanes and Haloarenes)

(Alcohols, Phenol and Ether)

(Aldehyde, Ketones)

(Nitrogen Containing Compounds)

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Organic Chemistry for the IIT-JEE is an invaluable book for all the students preparing for the prestigious

engineering entrance examination It provides class-tested course material and problems that will supplement any kind of coaching or resource the students might be using Because of its comprehensive and in-depth approach, it will be especially helpful for those students who do not have enough time or money to take classroom course.

A careful scrutiny of previous years’ IIT papers and various other competitive examinations during



the last 10 to 12 years was made before writing this book It is strictly based on the latest IIT syllabus (2009–10) recommended by the executive board It covers the subject in a structured way and familiar- izes students with the trends in these examinations Not many books in the market can stand up to this material when it comes to the strict alignment with the prescribed syllabus.

It is written in a lucid manner to assist students to understand the concepts without the help of any

This book is written to pass on to another generation, my fascination with descriptive inorganic chemistry Thus, the comments of the readers, both students and instructors, will be sincerely appreciated Any sugges- tions for added or updated additional readings would also be welcome.

Atul Singhal singhal.atul@yahoo.com

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me to present in this work.

I am thankful to my colleagues and friends, Deepak Bhatia, Er Vikas Kaushik, Er A R Khan, Vipul Agarwal, Er Ankit Arora, Er Wasim, Manoj Singhal, Vijay Arora, (Director, Dronacharya), Mr Anupam Shrivastav (Career Point, Kota), Mr Rajiv Jain (MVN, Faridabad), Mr Ashok Kumar, Mr Y.R Mittra and Mr N.C Joshi (Brillant Tutorials).

I am indebted to my father, B K Singhal, mother Usha Singhal, brothers, Amit Singhal and Katar Singh, and sisters, Ambika and Poonam, who have been my motivation at every step Their never-ending affection has provided me with moral support and encouragement while writing this book.

Last but not the least, I wish to express my deepest gratitude to my wife Urmila and my little,—but witty beyond years, daughters Khushi and Shanvi who always supported me during my work.

Atul Singhal singhal.atul@yahoo.com

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of multiple-choice questions.

INTRODUCTION

The word ‘organic’ means ‘pertaining of life’ The compounds like sugars, fats, oils, dyes, proteins, vitamins etc., which were isolated directly or indirectly from the living organisms like animals and plants were called organic compounds and their study is called Organic Chemistry The compounds like common salt, alum, nitre, blue and green vitriol etc., which were isolated from the non-living sources such as rocks and minerals were called inorganic compounds CO , CO2, CO3–2, HCO3–, HCN etc., not organic compounds.

VITAL FORCE THEORY OR BERZELIUS HYPOTHESIS

According to it the organic compounds cannot be synthesized in the laboratory because they require the ence of a mysterious force that is, vital force which exists only in the living organisms

pres-FALL OF VITAL FORCE THEORY OR WOHLER’S SYNTHESIS

According to Wohler when ammonium cyanate (obtained by double decomposition of ammonium chloride and potassium cyanate) is heated, urea is formed Urea was the ¿ rst organic compound to be prepared in lab

Amm cyanate O

NH4CNO Rearrangementheat NH2 – C – NH2

Urea

 General Organic Chemistry-1 (Nomenclature and Isomerism)

MODERN DEFINITION OF ORGANIC CHEMISTRY

Organic compounds may be de¿ ned as hydrocarbons and their derivatives and the study of hydrocarbons and their derivatives is called organic chemistry

For example, CH3OH, CH3CN etc

LARGE NUMBER OF ORGANIC COMPOUNDS

The main reasons for the large number of organic compounds are:

(i) Catenation The property of self-linking of carbon atoms through covalent bonds to form long straight or branched chains and rings of different sizes is called catenation Carbon shows maximum catenation in the periodic table and this property is primarily due to its small size, electronic con¿ guration and maximum bond energy or strength of carbon-carbon bonds for catenation

C > Si > S > P > …

(ii) Electronegativity and Strength of Bonds The electronegativity of carbon (2.5) is close to a number of other elements like Hydrogen (2.1), Nitrogen (3.0), Phosphorous (2.1), Chlorine (3.0), Oxygen (3.5) so it can form strong covalent bonds with these elements

(iii) Tendency to Form Multiple Bonds Due to its small size, carbon atom has a strong tendency to form multiple bonds with Carbon, Oxygen and Nitrogen atoms

(iv) Isomerism Many organic compounds show the phenomenon of isomerism by virtue of which a single molecular formula may represent two or more structures

Formaldehyde Formic acid

Equivalence of Four Carbon Valencies

All the four valencies of carbon are alike and symmetrical with respect to the atom that is, equal and lent to each other It is obvious from the fact that methane forms only one mono-substituted isomer, that is, monochloromethane on chlorination

equiva-General Organic Chemistry-1 (Nomenclature and Isomerism) 

Catenation Property of Carbon

Carbon atoms possesses a great tendency to link with one another The linking is possible through a

Single bond double bond

Carbon atoms may link to from

(a) an open chain which may be straight or branched

(b) a closed chain

Both are as follows:

(a) Open Chain

CLASSIFICATION OF ORGANIC COMPOUNDS

All the known organic compounds have been divided into following two classes:

Acyclic compounds (Aliphatic compounds)



Cyclic compounds (Aromatic compounds)



ACYCLIC OR OPEN CHAIN OR ALIPHATIC COMPOUNDS

The organic compounds in which all the carbon atoms are linked to one another to form open chains either straight or branched are called acyclic or open chain or aliphatic compounds

com- General Organic Chemistry-1 (Nomenclature and Isomerism)

Types of Cyclic Compounds These are of two types:

(a) Homocyclic Compounds Such compounds contain rings which are made up of only one kind of atoms

Carbocyclic Compounds

compounds

These are of following two types:

(i) Alicyclic Compounds These are carbocyclic compounds which resemble aliphatic compounds

in their properties

For example,

Cyclopropane cyclobutane cyclopentane Cyclohexane

(ii) Aromatic Compounds The compounds containing one or more fused or isolated benzene rings

are called Aromatic or Benzoid compounds

These are of following two types:

(i) Alicyclic Heterocyclic Compounds Such compounds resemble with aliphatic compounds in their

properties

For example,

NHO

Tetrahydrofuran (THF) Piperidine

(ii) Aromatic Heterocyclic Compounds Those compounds which resemble benzene and other

aro-matic compounds in most of their properties are called aroaro-matic heterocyclic compounds

For example,

N

NHO

Furan Pyrrole Pyridine

General Organic Chemistry-1 (Nomenclature and Isomerism) 

)XQFWLRQDO*URXS: It is an atom or a group of atoms present in a molecule which determines its chemical

properties, that is, site of chemical activity

For example, −OH (hydroxy), −CHO (aldehydic)

COOH (carboxylic) etc.

CLASSES OF CARBON ATOMS

3ULPDU\&DUERQ$WRPV



atom is called a primary carbon atom and it is represented by 1o or p.

 General Organic Chemistry-1 (Nomenclature and Isomerism)

CHARACTERISTICS OF HOMOLOGOUS SERIES

Any two successive members of a homologous series differ in their molecular formula by CH

and their molecular weights differ by 14

All the members can be prepared by a number of general methods

ary or tertiary hydrogen atoms respectively

The hydrogen atoms attached to primary, secondary, tertiary and quaternary carbon atoms in alkanes



are respectively three, two, one and zero

If a carbon atom is unsaturated it is not indicated as p, s, t carbon atom however it is counted for

General Organic Chemistry-1 (Nomenclature and Isomerism) 

IUPAC SYSTEM “International Union of Pure and Applied Chemists”

Basic Rules of nomenclature

Carbon chain length Root word ( Alk.) Carbon chain Root word

Oct-Selection of the longest chain of C-atoms

To write the IUPAC name, the ¿ rst step is to select the longest chain, that is parent or main chain.

CH 6C-atom chain [Longest here]

6C-atom chain [longest here]

 General Organic Chemistry-1 (Nomenclature and Isomerism)

For example, (2)

CH2

CH2C

6C-atom[longest possible chain]

5C-atom chain including (=) bond so it is preferred

If in a given compound there are two or more chains having similar number of C-atoms than a chain

5C-atom chain with 3-side chains so it is preferred

6 ‘C’-atom chain with 3-side so it is preferred here.

RULES FOR NUMBERING OF C-ATOMS OF THE CHAIN

For numbering of C-atoms of the chain priority order is given as follows:

General Organic Chemistry-1 (Nomenclature and Isomerism) 

OH

Br1

6

Prefer itNeglect it

1 2 3 4 5 Prefer it as CH3 has lower locant

CH3 — CH —CH —CH2 —CH3 number (2) while in case of Br-atom locant number is 3

2- bromo 3- chloro butane [correct]

3- bromo 2- chloro butane [incorrect]

 General Organic Chemistry-1 (Nomenclature and Isomerism)

3-ethyl 4-methyl hexane [correct]

4-ethyl 3-methyl hexane [incorrect]

Lowest Sum Rule

When numbering of a chain is possible from more than one side, prefer numbering of the chain from the side having lowest sum of all the locant numbers.

Since, in path (I) the sum is 24 whereas in path (II) it is 28 hence path (I) is preferred here for numbering.

Naming Of Complex Alkyl Substituents

When a side chain further include another side chain it is numbered and named as,

3[ 2’-bromo 1’-chloro] ethyl 2-methyl hexane

Pre¿ xes like bis, tris, tetrakis etc., can also be used to indicates the multiplicity of substituted substituent.

3, 3-bis [Bromomethyl] hexane

Use pre¿ xes like di, tri, tetra etc., in case of simple substituents with same times locant numbers



General Organic Chemistry-1 (Nomenclature and Isomerism) 

2, 2-dobromo 1, 1 dichloro propane

All pre¿ xes are written before alk (root word) as in above cases however, -ene, -yne or main functional

6-amino 6-bromo hept 2-ene 4-yn 1-al

If a compound has many functional groups the main functional group is named as suf¿ x name while

4-hydroxyl 5-keto hex-2-en 1-oic acid

FUNCTIONAL GROUP PREFERENCE TABLE

Pre¿ x name Functional Group Suf¿ x name

 General Organic Chemistry-1 (Nomenclature and Isomerism)

Pre¿ x name Functional Group Suf¿ x name

* In case carbon atom of the functional group is not countable name them as follows:

CH2 = CH—CH = CH2 │

CH3 3- methyl penta 1, 4 di-ene

CH3 —C≡C — CH —CH3 │

CH3 4-methyl pent 2-yne

5 2 3 2 1 Pent-1-ene-3-yne

CH3 2 3 4 5

1 C — CH2 — C ≡CH

CH2 2-methyl pent-1-ene 4-yne

+DORDONDQHVThese are named as follows

1, 1, 1 tri-chloro butane

-COOH (Carboxylic acid), -COOR (carbanoate),

-COCl (carbanoyl chloride), -CONH2 (carbanamide

or carboxamide), -CN (carbo nitrile), -CHO

General Organic Chemistry-1 (Nomenclature and Isomerism) 

HO

1’

2’

3 4 5

6 7

8

4’ 3’

2 2’

1 1’

(WKHUV[R —O —R]

Ethers are named as alkoxy alkanes

For example, Alkoxy Alkane C-atom alkyl group More C -atom alkyl group

4

Cl │1 2 3

CH3 —CH2 —O — CH —CH — CH3 │

Br Ethoxy 2-bromo 1-chloro propane

$OGHK\GHV>5²&+2@

These are named as Alkanals

Alkan + al → Alkanal For example,

Butanal CHO

│

CH = CH —CH3 But-2-en-1-al CHO │

CH2 —CH —CH3 │

OH 3- hydroxy butanal

C6H5 —CH = CH — CHO 3- phenyl-prop -2-en -1-al CHO

│

Butan 1, 4-di-al

 General Organic Chemistry-1 (Nomenclature and Isomerism)

3,3 -di-methoxy - pentanal

CHO

1234

These are named as alkanones.

Alkane + one → Alkanone

2

&DUER[\OLF$FLGV (R—COOH)

These are named as alkanoic acids.

Alkan + oic acid → Alanoic acid

4-(Hyroxylamino)-4-phenylbutanoic acid

—CH–CH2–CH2–COOH NHOH

CH3 —CH — CH2 — COOH │

OH 3- hydroxyl butanoic acid COOH

│

CH =CH —COOH But-2-ene1, 4 di-oic acid COOH

│

CH =CH —CH3 But 2-en-1-oic acid

1 CH2 —COOH │

2 CH—COOH │

3 CH2 —COOH Propane 1, 2, 3-tri-carboxylic acid

$FLGGHULYDWLYHV

CH3

CH3 —C —N ║ C2H5 O

N-ethyl N-methyl ethanamide CHO

│

CH =CH —COCl 4-oxo-but 2-en 1-oyl chloride

CH3 —CH2 —CO O

CH3—CH2 —CO Propanoic anhydride

General Organic Chemistry-1 (Nomenclature and Isomerism) 

123

4

5

Methyl 2-(1, 1)-dimethylethy) pantanoate

OCH2CH3Cl

C O

123

4

5 6

ethyl 3-chloro cyclohexane carboxylate

$PLQHV Amines are named as follows:

(A) 3ULPDU\$PLQHV [R —NH2]: These are called

amino alkanes or alkanamines

NH2

R R These are named as N-alkyl alkanamines.

CH2 — CH3

CH2 — CH3HN

CH2 — CH2 — CH3N-ethyl propanamine

4

5 6

(C) 7HUWLDU\DPLQHV51 

R

R —— N R N-N di alkyl alkanamine

or

N alkyl N’-alkyl-alkan amine

 General Organic Chemistry-1 (Nomenclature and Isomerism)For example,

1

2

5 6

5

2 1

2 3

(3)

NH2

CN OH

3-Amino 2-hydroxyl

cyclo hexene 1-carbonitrile

(6) C6H5CH2NC Benzyl carbyl amine

General Organic Chemistry-1 (Nomenclature and Isomerism) 

(xi) Br

Br OH

(xii)

OCH2 CH3

CO2H

(xiii)

CH2 │

CO2CH2CH3

(xvi)

 General Organic Chemistry-1 (Nomenclature and Isomerism)

12 3456 (vii) 1, 5-Cyclooctadiyne: Both triple bonds internal and endocyclic.

3 4 5

(xi) trans-2, 3-dibromo -2-buten-1-ol

(xii) 2-ethoxy-3-butynoic acid

(xiii) 4 (or para)-nitrophenyl 4 (or para)-chlorobenzoate

(xiv) dibutyl tetraphthalate

(xv) ethyl methyl malonate

(xvi) methyl succinate

2-Methyl-4-oxo-2-butenonitrile.

CH3 – C CH – C

CN

O H1

General Organic Chemistry-1 (Nomenclature and Isomerism) 

ISOMERISM

The compounds which differ in their properties but have same molecular formula are called isomers and the phenomenon is known as isomerism

TYPE OF ISOMERISM

Isomerism is of following three types:

Structural or constitutional isomerism

STRUCTURAL OR CONSTITUTIONAL ISOMERISM

In this type of isomerism, compounds possessing same molecular formula differ in their properties due to the difference in the linkages of atoms inside the molecule, that is, due to the difference in their structures Here isomers differ in the connectivity of carbon atoms that is, differ in structural formula Structural isomers dif- fer much in their physical as well as chemical properties

For example, CH3CH2OH and CH3OCH3 Both have the molecular formula C2H6O but they differ in their structures

Type of Structural Isomerism

It is of following types:

Chain or Skeleton or Nucleus Isomerism In this type of isomerism, compounds possessing same lecular formula differ in their properties due to the difference in the arrangement of carbon chain present in them The isomers differ in chain of carbon atoms that is, branched or unbranched chain Here a chain of minimum 4 carbon atoms is necessary to show this isomerism.

mo-For example,

CH3 – CH2 – CH2 – CH2 – CH2 –

Normal alkane

Neo alkaneIso alkane

 General Organic Chemistry-1 (Nomenclature and Isomerism)

For example, (2): Cyclo alkenes, alkynes and alkadienes & Q + Q±

General Organic Chemistry-1 (Nomenclature and Isomerism) 

(2) –NO2 (ntiro) and –ONO (Nitrite)

C2H5NO 2 (Nitro ethane) and C 2H5ONO (Ethyl nitrite)

(3) primary (RNH2), secondary (R2NH) and tertiary amines (R3N)

Metamerism It is the type of isomerism in which the compounds possessing same molecular formula differ

in their properties due to the difference in the alkyl groups present in them that is, same functional group but different alkyl groups attached to it It is shown by ether, thioether, ketones, esters, secondary amines, tertiary amines and alkenes

For example,

(1) CH3 – COOCH3 and HCOOC2H5 are metamers

(2) C2H5 – NH – C2H5 and CH3 – NH –CH2CH2CH3 are metamers

(3) C2H5 – O – C2H5 and CH3 – O – CH2CH2CH3 Or CH3 – O – CH(CH3)2

(4) C2H5 –NH – C2H5 and CH3 – NH – CH2CH2CH3 Or CH3 – NH – CH(CH3)2

 General Organic Chemistry-1 (Nomenclature and Isomerism)

Some Molecular Formulas and Possible Isomers

(i) $OFRKRODQG(WKHU&Q+Q2) It has alcohols, ethers and the possible isomerisms are functional,

positional , chain and metamerism

  &+2It has four alcohols and 3 ethers.(draw your self)

(5) &Q+Q2 The isomers having this molecular formula are Aldehyde, Ketone, Cyclic alcohol, Cyclic

ether, Unsaturated alcohol, Unsaturated Ether and Epoxyether Here possible isomerisms are tional, position and chain

func-For example, &+2

(6) &Q+Q2 The isomers having this molecular formula are Acid, Ester, Aldehyde with –OH group,

Ketone with –OH group and Cyclic ether with –OH group Here possible isomerisms are functional, position and chain

For example, &+2

OHCH

CH2O

General Organic Chemistry-1 (Nomenclature and Isomerism) 

O

(7) &Q+Q1 It has primary, secondary and tertiary amines and possible isomerisms are functional chain,

position and metamerism.

 General Organic Chemistry-1 (Nomenclature and Isomerism)

Tautomerism

Other Names: krytomerism, allelotropism, metrotropy, ketoenol isomerism It was introduced by Conard

Larr It is the type of isomerism in which the two functional isomers exist together in a dynamic equilibrium and the two forms existing in the equilibrium are called tautomers These forms are formed due to the migra- tion of H+ or proton (cation mainly) due to which bond position changes (Desmotropism) The migration of

H+ or proton is called cationtropism or prototropism The least stable form is called labile form

(shifting of ‘H’ from P to R) The migration of cation is possible in following two ways:

'LDG6\VWHP Here H+ (cation) migrates to next atom

CH – CH3 2 – C – NH2 ↔ CH 3 – CH2 – C = N – H

Keto-enol Isomerism It is the most common type of tautomerism in which the two tautomeric forms are keto and enol forms which are formed as a result of migration of α - hydrogen atom The presence of α - hydrogen atoms is must here, however, α – C – atom must not be unsaturated

General Organic Chemistry-1 (Nomenclature and Isomerism) 

Unsaturated

O

OO

These cannot show tautomerism as all α-carbon atoms are unsaturated so migration of α-H-atom is not possible Enol content

Enol content

Enol content α Number of carbonyl groups

In acyclic β-diketones generally enol content is higher

OO

In this case, enol form is stabilized by extended conjugation and Intramolecular hydrogen bonding

Enol Content in Decreasing Order

O

> C6H5COCH2COCH3 >CH3COCH2

COCH3 > CH3COCH2COOC2H5 > CH3COCH2CHO > CH3COCH3 > CH3CHO

 General Organic Chemistry-1 (Nomenclature and Isomerism)

Some Specifi c Examples of Tautomerism

(i) Nitroso-oxime tautomerism

R2CH –N = 4 = O ⇌ R2C=N –OH

(nitroso) (oxime)

(ii) Nitro-acinitro tautomerism

General Organic Chemistry-1 (Nomenclature and Isomerism) 

(iv) Amide-imidol tautomerism

STEREO ISOMERISM OR SPACE ISOMERISM

In this type of isomerism, the compounds possessing same molecular formula differ in their properties due to the difference in the arrangement in space of their atoms or groups in the molecule

Types of Stereo Isomerism

It is of following types:

(1) Geometrical Isomerism

It is the type of isomerism in which the compounds possessing same molecular formula differ in their properties due to the difference in their geometry that is, due to the difference in the direction of attach- ment of same atoms or groups in their molecule It is not shown by single bonded compounds like (C–C) due to free rotation

C

C

Head to head or free rotation is possible here so no geometrical isomerism is possible.

It is shown by [>C = C< ], [>C = N – ] [ – N = N – ] , cyclo alkanes.

Geometrical Isomerism in Alkenes and Cyclo Alkanes

CMeEt

CMeEt

 General Organic Chemistry-1 (Nomenclature and Isomerism)Butene – 1 also does not show geomatrical isomerism.

Maleic acid Fumeric acid

For example, 2-Butene

Diff erence between Cis and Trans Forms

Cis:

Cis is more reactive but less stable form as the same species are on the same side so steric repulsion



increases reactivity and decreases stability

The dipole moment of cis is more



It has less melting point as same groups are on same side



General Organic Chemistry-1 (Nomenclature and Isomerism) 

*HRPHWULFDO,VRPHULVPLQ&\FOR$ONDQHV

XXX

X

A

AA

AA

A

A

A

BB

B

BCis

A It cannot show geometrical isomerism as one carbon atom has two similar species ‘A’

The boiling point of cis is more

For example, trans-2-pentene has some dipole moment value but less than cis form

Have more melting point than cis

According to it the organic compounds cannot be synthesized in the laboratory because they require the ence of a mysterious force that is, vital force which... molecular formula differ in their properties due to the difference in the linkages of atoms inside the molecule, that is, due to the difference in their structures Here isomers differ in the connectivity... It is the type of isomerism in which the two functional isomers exist together in a dynamic equilibrium and the two forms existing in the equilibrium are called tautomers These forms are formed