11C12�

Organic Chemistry – Some Basic Principles and Techniques

Catenation

ORGANIC CHEMISTRY

11C12.1��Introduction to Organic Chemistry

Learning Objectives

​

Introduction

​

Representation

​

Nomenclature of Alkanes

​

Nomenclature of Compounds with Functional Group

​

Nomenclature of Aromatic Compounds

11C12.1 Introduction to Organic Chemistry

11C12.1

​

CV 1

​

Introduction

Organic compounds are vital for sustaining life on earth

Deoxyribonucleic acid (DNA)

Guanine (G)

Blood

Muscle

Fuels

Octane

Fuels (Petrol)

Polymer

Polyvinyl chloride

Dyes

Crystal Violet Dye

Crystal Violet Structure

Medicine

Aspirin

Aspirin Structure

Jacob Berzilius

Proposed that ‘vital force’ was responsible for formation of organic compounds.

Synthesis of Organic Compounds

Synthesis of Organic Compounds

Synthesised an organic compound, urea from an inorganic compound, ammonium cynate.

F. Wohler

ammonium cynate

Urea

Heat

Synthesis of Organic Compounds

Hermann Kolbe

Synthesised

Acetic acid

Synthesis of Organic Compounds

Marcellin Berthelot

Synthesised

Methane

Organic compounds could be synthesised from inorganic

sources in a laboratory

Shape of Carbon Compounds

Tetravalence of Carbon and the formation of covalent bonds by it are explained in terms of :

Hybridisation of s and p orbitals

Shape of Carbon Compounds

Contains more s-character

Closer to its nucleus and forms shorter and stronger bonds

More electronegative

Q.

Write the state of hybridisation of carbon in the following compounds

and shapes of each of the molecules.

Sol.

mutually parallel

perpendicular

to the plane

Easily available to the attacking reagents

Classification of Organic Compounds

Organic Compounds

Acyclic or Open

chain Compounds(I)

Cyclic or Closed

Chain or Ring Compounds(II)

Homocyclic or

Carbocyclic compounds

Heterocyclic

compounds

Alycyclic

compounds

Aromatic

compounds

Benzenoid

Compounds

Non-benzenoid

Compounds

Acyclic or Open Chain Compounds

Consist of straight or branched chain compounds,

also called aliphatic compounds

Ethane

Isobutane

Acetaldehyde

Acetic acid

Alicyclic or Closed Chain or Ring Compounds

Contain carbon atoms joined in

the form of a ring

Sometimes atoms other than carbon

are also present in the ring

Homocyclic Compounds

Heterocyclic Compounds

Cyclopropane

Cyclohexane

Tetrahydrofuran

Thiophene

Aromatic Compounds

These include benzene and other related ring compounds

Benzenoid

aromatic compound

Benzene

Aniline

Naphthalene

Non-benzenoid

compound

Azulene

Tropolone

Hetereocyclic Aromatic Compounds

Furan

Thiophene

Pyridine

Classified on the basis of –

• functional group

• families or homologous groups

Functional Group

Atom or group of atoms joined in a specific manner which is responsible for the characteristic chemical properties of organic compounds.

Homologous Series

A group or a series of organic compounds each containing a characteristic functional group forms a homologous series.

Homologous series

of Alcohols

Group of organic

compound

The members of the series are called homologues.

Homologous series

of Alkanes

ConcepTest

​

Ready for Challenge

Q.

Pause the video

Time duration: 1 minute

Sol.

Q.

11C12.1

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CV 2

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Representation of Organic Compounds

Structural Representation of Organic Compounds

Structural Formula

Lewis structure or dot structural formula

Dash structural formula

Condensed structural formula

Bond-line structural formula

Lewis Structure or Dot Structural Formula

A pair of electrons forming a covalent bond is represented by

using a dot or cross

Dot structure

Cross structure

Dash Structural Formula

• A pair of electrons forming a single covalent

bond is represented by a line.

• A double bond is represented by a double line.

• A triple bond is represented by a triple line.

Dash Structural Formula

Lone pair

Formaldehyde

Dash Structural Formula

Double

Single

Formaldehyde

Dash Structural Formula

Ethane

Ethene

Ethyne

Methanol

Also called Complete structural formulas

or

Condensed Structural Formula

Ethane

Ethene

Ethyne

Methanol

Condensed Structural Formula

Further condensed

For Octane

For 4,5-Dimethylhexanol

Further condensed

Bond-line Structural Formula

Carbon and hydrogen are not shown and the lines representing

carbon-carbon bonds are drawn in zig-zag fashion

Terminals represent

methyl group

(a)

(b)

(c)

Bond-line Structural Formula

(a)

(b)

(c)

The only atoms specifically written are oxygen, chlorine, nitrogen etc.

Bond-line Structural Formula

In cyclic compounds -

Cyclopropane

Cyclopentane

Chlorocyclohexane

Three Dimensional Representation of Organic Molecules

Dashed wedge

(bond away from observer)

Solid wedge

(bond towards observer)

Bonds in the

plane of paper

Molecular Model

Physical devices that are used for better visualisation and perception of

3-D shapes of organic molecules

Wood

Plastic

Metal

Molecular Model

Framework model

Ball-and-stick model

Space filling model

Molecular model

11C12.1

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PSV 1

Q.

Write the bond-line structure of the following compounds?

Sol.

1. Isopropyl alcohol

2. 2,3-Dimethylbutanal

3. Heptan-4-one

11C12.1

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CV 3

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Trivial Names of Organic Compounds

Trivial or Common Names

Marsh gas

Methane

Before IUPAC system of nomenclature, organic compounds were assigned

names based on their origin or certain properties

Trivial or Common Names

Citrus fruit

Citric acid

Trivial or Common Names

Red ant

Formic acid

Latin word for ant is Formica

Trivial or Common Names

Geodesic dome by the famous

architect R. Buckminsterfullerene

Buckminsterfullerene

Common Names of some Organic Compounds

11C12.1

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CV 4

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Nomenclature of Hydrocarbons

Systematic method of naming an organic compound

International Union of Pure and Applied Chemistry (IUPAC)

Names are correlated with the structure such that the reader or listener

can deduce the structure from the name.

Ethane

For e.g. -

The IUPAC System of Nomenclature

The IUPAC System of Nomenclature

A systematic name of an organic compound is derived by identifying the

hydrocarbon and the functional group attached to it

Parent chain

Functional group

Branch

Compounds containing carbon and hydrogen only are called hydrocarbon

Saturated

Unsaturated

IUPAC name for a homologous series

of such compound is alkane

or

Sec. Prefix + Pri. Prefix + Root Word + Pri. Suffix + Sec. Suffix

No. of Carbon atom in Parent Chain

Cyclic Compound �Cyclo-

Substituents with locants

Unsaturation�-ane

-ene

-yne

Main functional group

The IUPAC System of Nomenclature

Sec. Prefix + Pri. Prefix + Root Word + Pri. Suffix + Sec. Suffix

The IUPAC System of Nomenclature

IUPAC Nomenclature of Hydrocarbons

Alkane :

Alkene :

Alkyne :

Single bond

Double bond

Triple bond

Eth + ane

Eth + ene

Eth + yne

Ethyne

Ethene

Ethane

The names of such compounds are based on their chain structure

Ends with a suffix ‘-ane’

Straight chain hydrocarbons

IUPAC Nomenclature of Hydrocarbons

11C12.1

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CV 5

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Nomenclature of Branched

Chain Alkanes

Branched Chain Hydrocarbon

Small chains of carbon atoms are attached at one or more carbon

atoms of the parent chain

The small carbon chains are called alkyl groups

Methane

Methyl

Branched Chain Hydrocarbon

Some Alkyl Groups

The alkyl groups can be branched also

Isopropyl

sec-Butyl

Isobutyl

tert-Butyl

Neopentyl

Branched Chain Hydrocarbon

Nomenclature of Branched Chain Alkanes

1. Longest carbon chain in the molecule is identified

I

II

2. The numbering is done in such a way that the branched carbon atoms get the lowest possible numbers.

I

II

Nomenclature of Branched Chain Alkanes

Lowest locant rule

3. Names of alkyl groups attached as a branch are then prefixed to the name of the parent alkane and position of substituents is indicated by appropriate number.

6-Ethyl-2-methylnonane

Nomenclature of Branched Chain Alkanes

6-Ethyl-2-methylnonane

• If different alkyl groups are present, they are listed in alphabetical order

Numbers are separated from

groups by hyphen

No break/gap

3. Names of alkyl groups attached as a branch are then prefixed to the name of the parent alkane and position of substituents is indicated by appropriate number.

Nomenclature of Branched Chain Alkanes

4. If two or more identical substituent groups are present then numbers are separated by commas (,).

Names of identical substituents are not repeated instead prefixes such as -

di-for 2

tri-for 3

tetra-for 4

penta-for 5

hexa-for 6

2,4-Dimethylpentane

2,2,4-Trimethylpentane

3-Ethyl-4,4-dimethylheptane

Nomenclature of Branched Chain Alkanes

5. If two substituents are found in equivalent position , the lower number is given to the one coming first in the alphabetical listing.

3-Ethyl-6-methyloctane

6-Ethyl-3-methyloctane

I

II

Nomenclature of Branched Chain Alkanes

6. The carbon atom of the branch that attaches to the root alkane is numbered “1”.

1,3 –Dimethylbutyl-

Nomenclature of Branched Chain Alkanes

6. The carbon atom of the branch that attaches to the root alkane is numbered “1”.

5-(1,2-Dimethylpropyl)-3-ethyldecane

placed in parenthesis while naming the compound

Nomenclature of Branched Chain Alkanes

5-Sec-butyl-4-isopropyldecane

Nomenclature of Branched Chain Alkanes

• If there happens to be two chains of same size, then that chain is to be selected which contains more number of side chains.

5-(2-Ethylbutyl)-3,3-dimethyldecane

5-(2,2-Dimethylbutyl)-3-ethyldecane

• Numbering is to be done from the end closer to the substituent.

Nomenclature of Branched Chain Alkanes

Q.

Sol.

Write the IUPAC name of the following organic compound.

Longest parent chain - Nonane

Branched chain alkyl group – 2,2-Dimethylpropyl

IUPAC name :

5-(2,2-Dimethylpropyl)nonane

Nomenclature of Cyclic Compounds

Saturated monocyclic compound is named by prefixing ‘cyclo’ to the

corresponding straight chain alkane.

Cyclopentane

1-Methyl-3-propylcyclohexane

3-Ethyl-1,1-dimethylcyclohexane

Alphabetical order

of numbering

ConcepTest

​

Ready for Challenge

Q.

Structures and IUPAC names of some hydrocarbons are given below.

Explain why the names given in parentheses are incorrect.

​

I

II

2,5,6-Trimethyloctane

[and not 3,4,7-Trimethyloctane]

3-Ethyl-5-methylheptane

[and not 5-Ethyl-3methylheptane]

Pause the video

Time duration: 1 minute

Q.

Structures and IUPAC names of some hydrocarbons are given below.

Explain why the names given in parentheses are incorrect.

​

Sol.

1. Lowest locant number, 2,5,6 is lower than 3,4,7

2. Lower number is given to the one that comes first in the name

according to alphabetical order

I

II

2,5,6-Trimethyloctane

[and not 3,4,7-Trimethyloctane]

3-Ethyl-5-methylheptane

[and not 5-Ethyl-3methylheptane]

11C12.1

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PSV 2

Q.

Give the IUPAC names of the following compounds?

Sol.

a.

b.

a.

Hex-1-en-5-yne

b.

Hex-4-en-1-yne

Lowest locant rule

Double bond is

given higher priority

11C12.1

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CV 6

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Nomenclature of Compounds with

One Functional Group

​

Functional Group

• An atom or a group of atoms bonded together in a unique manner which is usually the site of chemical reactivity in an organic molecule.

2 Na

The presence of functional groups enables systematisation of organic

compounds into different classes

Liberates

dihydrogens gas

Functional Group

Functional Group

Functional Group

STEP 1 – Identify the functional group in the compound.

Functional group

Alcohol

Suffix : ol

Functional Group

STEP 2 – Number the longest chain, assign the lowest number to the carbon possessing functional group.

Lowest possible

number is 2

Functional Group

STEP 3 – Assign a root word.

Functional Group

STEP 4 – Assign a primary suffix

Single bond

Functional Group

STEP 5 – Assign a secondary suffix.

Alcohol

Functional Group

STEP 6 – Assign a secondary suffix.

IUPAC Name – Pentan-2-ol

Functional Group

IUPAC Name – Hex-2-en-4-ynoic acid

• "Ene" comes before "yne" in the name, no matter what the locants (numbers) are.

Functional Group

11C12.1

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CV 7

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Nomenclature of Compounds with

More than One Functional Group

​

Functional Group

Ketone

Carboxylic acid

Functional Group

Main functional group : Carboxylic acid

Functional Group

Decreasing order of priority

Functional Group

Main functional group

Substituent

Lower priority

Higher priority

Functional Group

Main functional group

Carboxylic group suffix is ‘-oic acid’

Functional Group

Carboxylic group suffix is ‘-oic acid’

Substituent

Prefix for ketone is ‘oxo-’

Functional Group

Single bond “ane”

Substituent “oxo”

Principal functional group “oic acid”

Position of prefix “5”

Longest chain with six carbon atoms “6”

5-Oxohexanoic acid

5-

Oxo

hexan

oic

acid

Functional Group

diol

Eth

ane

Ethan-1,2-diol

Functional Group

7-Hydroxyheptan-2-one

2-Oxoheptan-7-ol

11C12.1

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PSV 3

Q.

Give the IUPAC names of the following compounds?

Sol.

a.

b.

c.

d.

1. 3-Bromo-3-chloroheptane

2. 3-Methylpentanenitrile

3. 3-Chloropropanal

4. 2,2-Dichloroethanol

11C12.1

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CV 8

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Nomenclature of Aromatic Compounds

​

Nomenclature of Substituted Benzene Compounds

Methylbenzene

(Toluene)

Methoxybenzene

(Anisole)

Aminobenzene

(Aniline)

Nitrobenzene

Bromobenzene

Substituent is placed as prefix to the word benzene

Benzaldehyde

Benzoic Acid

Phenol

Lowest Number

1,3-Dibromobenzene

Lowest number

Nomenclature of Substituted Benzene Compounds

Lowest Number

1,3-Dibromobenzene

1,5-Dibromobenzene

Not Lowest number

Nomenclature of Substituted Benzene Compounds

1,2-Dibromobenzene

1,3-Dibromobenzene

1,4-Dibromobenzene

In trivial system of nomenclature the terms ortho(o), meta(m) and para(p) are used as.

m-Dibromobenzene

o-Dibromobenzene

p-Dibromobenzene

Nomenclature of Substituted Benzene Compounds

In some cases, common name of benzene derivatives is taken as

base the compound

1-Chloro-2,4-dinitrobenzene

2-Chloro-4-nitrotoluene

Nomenclature of Substituted Benzene Compounds

Q.

Sol.

Write the structure of following :

1. 2-Chloro-4-methylanisole

2. 4-Ethyl-2-methylaniline

3. 3,4-Dimethylphenol

2-Chloro-4-methylanisole

4-Ethyl-2-methylaniline

3,4-Dimethylphenol

Benzene ring

Alkane with

functional group

Substituent

Parent chain

2,3-Dibromo-1-phenylpentane

Nomenclature of Substituted Benzene Compounds

SUMMARY

• Sec. Prefix + Pri. Prefix + Root Word + Pri. Suffix + Sec. Suffix

No. of Carbon atom in Parent Chain

Cyclic Compound �Cyclo-

Substituents with locants

Unsaturation�-ane

-ene

-yne

Main functional group

SUMMARY

Decreasing order of priority

Reference Questions

NCERT Exercise Questions : 12.1 to 12.8

11C12.1 Introduction to Organic Chemistry

NCERT In text Questions : 1 to 10

Workbook Questions : 1 to 9 , 11 , 12 , 13, 16,

11C12.2��Isomerism in Organic Compounds

Learning Objectives

​

Isomerism

​

Chain and Position Isomerism

​

Functional Isomerism

​

Geometrical Isomerism

​

Optical Isomerism

11C12.2 Isomerism

11C12.2

​

CV 1

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Isomerism

Isomerism

Jacob Berzelius

Isos + meros

ISOMER

Greek word

equal

parts

Isomerism

The phenomenon of existence of two or more compounds possessing the

same molecular formula but different properties

Propanone

Propanal

Isomer

Isomerism

Some more examples -

Isomerism

Isomerism

Structural isomerism

Stereoisomerism

Chain isomerism

Position isomerism

Functional group

isomerism

Metamerism

Geometrical isomerism

Optical isomerism

11C12.2

​

CV 2

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Chain and Position Isomerism

Structural Isomerism (2D)

Compounds having the same molecular formula but different structures

2-Aminophenol

3-Aminophenol

4-Aminophenol

Chain Isomerism

When two or more compounds have similar molecular formula but

different carbon skeleton

Pentane

Isopentane

Neopentane

2-Methylbutane

2,2-Dimethylpropane

Position Isomerism

When two or more compounds differ in the position of substituent

or functional group on the carbon skeleton

Propan-1-ol

Propan-2-ol

Propanamine

Propan-2-amine

Position Isomerism

All the normal, iso and neo compounds are always chain isomers except

n-propyl and Isopropyl

Calculation of position for a group

a

a

a

b

a

1 way

2 ways

Position Isomerism

a

b

b

a

a

b

a

a

a

b

c

b

a

a

d

c

a

b

a

a

a

a

4 ways

2 ways

2 ways

8 ways

3 ways

4 ways

1 ways

11C12.2

​

PSV 1

Q.

Chain isomer of 2-Hexyne is :

1. 1-Hexyne

2. 3-Methylpent-1-yne

3. Hexadiene

4. 4-Methylhex-2-yne

Sol.

2-Hexyne

Chain isomers

3-Methylpent-1-yne

11C12.2

​

CV 3

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Functional Isomerism and Metamerism

Functional Isomerism

Two or more compounds having the same molecular formula but different

functional groups are called functional isomers

Propanone

Propanal

Ketone

Aldehyde

Types of Functional Isomerism

1. Alcohols + Ethers

2. Aldehydes + Ketones

3. Cynides + Isocynides

5. Acid + Ester

6. Alkene + Cycloalkane

7. Alkyne + Alkadiene + Cycloalkene + Bicycloalkane

Types of Functional Isomerism

1. Alcohols + Ethers

For e.g.-

Types of Functional Isomerism

2. Aldehydes + Ketones

For e.g.-

Aldehyde

Ketone

3. Cynides + Isocynides

and

Types of Functional Isomerism

For e.g.-

Types of Functional Isomerism

5. Acid+Ester

For e.g.-

Acid

Ester

Types of Functional Isomerism

5. Alkene+Cycloalkane

For e.g.-

Alkene

Cycloalkane

Metamerism

It arises due to different number of C-atom on either side of functional group or hetero-atom in the molecule.

Note : Poly-valent functional group must be present

Ether

Ketone

Amine

Thioether

Min. 4 C

Min. 4 C

Min. 4 C

Min. 5 C

For e.g.-

Metamerism

R+R’ : min 4 C

Does not show metamerism

ConcepTest

​

Ready for Challenge

Q.

Pause the video

Time duration: 1 minute

Q.

Sol.

Acid

Ester

11C12.2

​

CV 4

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Geometrical Isomerism

Stereoisomerism

The compounds that have the same constitution and sequence of covalent

bonds but differ in relative positions of their atoms or groups in space

Geometrical Isomerism

Optical Isomerism

Geometrical Isomerism

Geometrical Isomerism

Geometrical Isomerism

Geometrical Isomerism

Geometrical Isomerism

Conditions for Geometrical Isomerism

2. Both the atoms or groups joint with doubly bonded carbon must be different(never be same)

Ex. :

Cis-

Trans-

b

a

b

a

b

b

a

a

Geometrical Isomerism in Alkene

• Do not show geometrical isomerism.

Same spatial arrangement

Same spatial arrangement

Geometrical Isomerism in Alkene

Different spatial arrangement

Different spatial arrangement

• Show geometrical isomerism.