12C13��Amines

Introduction to Amines

Ammonia

Amine

Importance of Amines

Medicine

Ephedrine

Adrenaline

Polymers

Fibre

Dye

Used to treat B.P problems

12C13.1��Structure, Classification, Nomenclature and preparation of Amines

Learning Objectives

12C13.1 Structure, Classification, Nomenclature and preparation of Amines

Structure, classification and nomenclature of amines

Preparation of amines

12C13.1

​

CV 1

​

Structure, Classification and Nomenclature of Amines

Structure of Amines

Carries an unshared pair of electrons

N atom of amines is trivalent

Geometry is pyramidal

Classification of Amines

Secondary

Primary

Tertiary

Nomenclature of Amines

Ethylamine

Isopropylamine

Ethylmethylamine

Trimethylamine

Diethylbutylamine

Allylamine

Aniline

o-Toluidine

Common names

Prefix alkyl + amine

Nomenclature of Amines

IUPAC names

Alkane

2- If more than one amino groups are present at different positions in parent chain

1- Simple amines

Alkane

3- If alkyl groups are directly attached to N atom

Notation: N-alkyl

+ amine

+ amine

Nomenclature of Amines

Ethanamine

Propan-2-amine

N-Methylethanamine

N,N-Dimethylmethanamine

N,N-Diethylbutan-1-amine

Prop-2-en-1-amine

Aniline

2-Methylaniline

or

Benzenamine

12C13.1

​

PSV 1

Q.

Classify the following as primary, secondary and tertiary amines.

1

2

3

4

Sol.

1

2

3

4

Primary

Secondary

Tertiary

Primary

12C13.1

​

PSV 2

Q.

Pause the video

Time duration: 2 minute

Sol.

Butanamine

Butan-2-amine

2-Methylpropan- 2-amine

2-Methylpropanamine

Sol.

N-Ethylethanamine

N-Methylpropanamine

N-Methylpropan-2-amine

N,N-Dimethylethanamine

12C13.1

​

CV 2

​

Preparation of Amines

Reduction of nitro compounds

Nitrobenzene

Nitrosobenzene

Phenylhydroxylamine

Aniline

Reduction

Reduction

Reduction

Reduction

Ammonolysis of Alkyl Halides

Alkyl / Benzyl halides

Ammonolysis of Alkyl Halides

Mechanism

Reduction of Nitriles

Nitrile

Amine

Reduction

Reaction is used for ascent of amine series

Methyl nitrile

Ethanamine

Reduction of Amides

Amide

Amine

Ethanamide

Ethanamine

Gabriel phthalimide synthesis

Phthalimide

Phthalic acid

Good method to form primary aliphatic amines

Aromatic primary amines cannot be prepared by this method

Gabriel phthalimide synthesis

Phthalimide

Potassium Phthalimide

N-Alkylphthalimide

Sodium phthalate

Phthalic acid

Hoffmann bromamide degradation reaction

Amide

Amine

Good method to form primary amines

Migration of alkyl or aryl group from carbonyl carbon of amide to nitrogen atom

O

R

C

N

Amide

Mechanism

N-Bromoamide

Hoffmann

rearrangement

Carbamic acid

Carbamate

Hoffmann bromamide degradation reaction

12C13.1

​

PSV 3

Q.

Write structures and IUPAC names of -

​

(i) the amide which gives propanamine by Hoffmann bromamide

reaction.

​

(ii) the amine produced by the Hoffmann degradation of benzamide.

propanamine

Amide used

Butanamide

Sol.

Amide

Amine

Hoffmann Bromamide reaction

(i) the amide which gives propanamine by Hoffmann bromamide reaction.

Sol.

Amide

Amine

(ii) the amine produced by the Hoffmann degradation of benzamide.

Benzamide

Amine formed

Aniline

Hoffmann Bromamide reaction

ConcepTest

​

Ready for Challenge

Q.

Write the product of the following Reaction :

Pause the video

Time duration : 2 minutes

Sol.

Gabriel phthalimide reaction :

Phthalimide

Potassium Phthalimide

N-Ethylphthalimide

Sodium phthalate

Ethylamine

Summary

Structure of amines

Preparation of amines

Gabriel phthalimide synthesis

Hoffmann bromamide degradation reaction

Reference Questions

NCERT Exercise Questions: 13.1, 13.7 (iii), (vii), 13.8 (v), (vi), 13.10, 13.12,

Workbook Question: 3, 9, 17 (i), 20 (iii),

12C13.1 Structure, Classification, Nomenclature and

preparation of Amines

NCERT Intext Questions: 13.1, 13.2 (i), (ii), 13.3

Nitration

Reduction

Methylation

Methylation

Benzene

12C13.2��Properties of Amines

Learning Objectives

12C13.2 Properties of Amines

Physical properties of Amines

Basic character of Amines

Alkylation and Acylation of Amine

Carbylamine Reaction, Action of Nitrous acid and Hinsberg’s Test

12C13.2

​

CV 1

​

Physical properties of Amines

Physical states of Amines

Lower aliphatic amines are gases with fishy odour

Primary amines (>3 C) liquid and higher are solid.

Solubility of Amines

Hydrophobic part

Hydrophilic part

Water insoluble

water soluble

due to H-bonding

Hydrogen bonding

Solubility of Amines v/s Alcohol

Stronger Hydrogen bonding

Amines

Alcohol

Alcohols are more soluble in water than Amines

Amines are soluble in organic solvents like -

Solubility of Amines

Alcohol

Ether

Benzene

Boiling point of Amines

Comparison of boiling point of some organic compound with similar

molecular mass

Order of boiling point

Alkane

Alcohol

Boiling point of Amines

12C13.2

​

CV 2

​

Basic character of Amines

Basic character of Amines

(Salt)

Aniline

Anilinium chloride

Show basic character

Basic Character of Amines in terms of K_b value

Stronger base

Increasing order of Basic strength

Basic Character of Amines in terms of K_b value

Basic strength in Gaseous phase

Stability of conjugate acid depends upon I effect

+I

Order of basic strength

Conjugate Acid

Conjugate Acid

(b) Alkanamines v/s ammonia

Extent of H-bonding in water and order of stability of ions by solvation.

Basic strength in Aqueous phase

Depends upon

​

• Inductive effect

​

• Solvation effect

​

• Steric hindrance

Less +I

More solvation

Less steric hindrance

Moderate +I

Moderate solvation

Moderate steric hindrance

More +I

Less solvation

More steric hindrance

Basic strength in Aqueous phase

Overall order of basic strength

Methyl substituted amine

Ethyl substituted amine

Basic strength in Aqueous phase

Basic character - Arylamines v/s Ammonia

Show basic character

Ammonia

H

H

Ammonium ion

Aniline

Unshared e^-pair of Aniline is less available for protonation due to resonance

Ammonia is more basic than aniline

Resonating structure of aniline

Basic character - Arylamines v/s Ammonia

So aniline is more stable than anilinium ion

Effect of substituents on Basic character

Groups: +m effect or +I effect EDG

Groups: -m effect or -I effect EWG

Order of basic strength

12C13.2

​

PSV 1

Q.

Select more basic amine from each of the following pair of compounds.

(a)

or

(b)

or

Sol.

Basic strength

More basic

less basic due to e^- involved in resonance

(a)

(b)

Order of E.N.

>

More basic

Less basic

ConcepTest

​

Ready for Challenge

Q.

Arrange the following:

Pause the video

Time duration: 2 minute

Sol.

Aliphatic amine are more basic than aromatic amine

Increasing order of basic strength

<

<

<

>

>

>

(a)

(b)

Increasing order of basic strength

<

<

<

12C13.2

​

CV 3

​

Alkylation and Acylation of Amine

Alkylation Reaction

Primary amine

Secondary amine

Tertiary amine

Quaternary ammonium salt

Acylation Reaction

Ethanamine

N-Ethylethanamide

Benzenamine

Acetic anhydride

Acetanilide

Amines

Acid Chloride,

Anhydride,

Ester

Amides

Pyridine

Removes HCl

Acyl chloride

Acylation Reaction

Example :

Mechanism :

Amine

Acyl chloride

N-Ethylethanamide

Methanamine

Benzoyl Chloride

N-Methylbenzamide

Benzoylation Reaction

12C13.2

​

CV 4

​

Carbylamine Reaction, Action of Nitrous acid and Hinsberg’s Test

Carbylamine Reaction

Test for primary amines only

Chloroform

Potassium

Hydroxide

Isocyanide

Foul smell

Aliphatic amine/

Aromatic amine

Isocyanide Test

Mechanism

Dichlorocarbene

(Electrophile)

Isocyanide

Carbylamine Reaction

Reaction with Nitrous acid

Nitrous acid

Alkyl diazonium chloride

Aliphatic amine

Alcohol

Reaction with Nitrous acid

Aniline

Benzenediazoniumchloride

Diazotisation

Hinsberg’s test - Reaction with Arylsulphonyl Chloride

Benzenesulphonyl chloride

Hinsberg’s Reagent

Used to distinguish primary, secondary and tertiary amines

Reaction with secondary amine :

N,N-Diethylbenzenesulphonamide

Insoluble in Alkali

No acidic hydrogen

Reaction with Tertiary amine :

Tertiary amines do not react

Reaction with Primary amine :

N-Ethylbenzenesulphonamide

Soluble in Alkali

Strongly acidic

Hinsberg’s test - Reaction with Arylsulphonyl Chloride

12C13.2

​

PSV 2

How will you convert benzene to N,N-Dimethylaniline?

Q.

Nitration

Reduction

Methylation

Methylation

Benzene

Sol.

Aniline

Nitrobenzene

N-Methylaniline

N,N-Dimethylaniline

12C13.2

​

PSV 3

​

​

How will you convert nitromethane to dimethyl amine?

Q.

Sol.

Carbylamine Reaction

Reduction

Nitro methane

Methanamine

Methyl isocyanide

Dimethyl amine

ConcepTest

​

Ready for Challenge

Give a chemical test to distinguish the following pairs of compounds.

​

1. Methylamine and dimethylamine

​

• Secondary and tertiary amines

Q.

Pause the video

Time duration: 3 minute

(i) Methylamine and dimethylamine

Sol.

Methylamine

Dimethylamine

Primary amine

Secondary amine

Isocyanide

Foul smell

No Reaction

Carbylamine Test :

Secondary and tertiary amine can be distinguished by Heisenberg test

Benzenesulphonyl chloride

Isoluble in Alkali

No acidic hydrogen

Tertiary amines do not react with benzenesulphonyl chloride

N,N-Diethylbenzenesulphonamide

(ii) Secondary and tertiary amines

Sol.

12C13.3��Electrophilic Substitution Reaction of Amines

Learning Objectives

12C13.3 Electrophilic Substitution Reaction of Amines

Bromination

Nitration and Sulphonation

12C13.3

​

CV 1

​

Bromination

Resonance structures of aniline

Electrophilic Aromatic Substitution in Amines

C

C

C

C

C

H

H

H

H

H

C

-o and -p are the more favourable sites for electrophilic attack

Electrophilic Aromatic Substitution in Amines

C

C

C

C

C

H

H

H

H

H

C

Electrophilic Aromatic Substitution in Aniline

C

C

C

C

C

H

H

H

H

H

C

Electrophilic Aromatic Substitution in Aniline

C

C

C

C

C

H

H

H

H

H

C

Electrophilic Aromatic Substitution in Aniline

C

C

C

C

C

H

H

H

H

H

C

Electrophilic Aromatic Substitution in Aniline

C

C

C

C

C

H

H

H

H

H

E

C

Electrophilic Aromatic Substitution in Aniline

C

C

C

C

C

H

H

H

H

H

E

C

Electrophilic Aromatic Substitution in Aniline

C

C

C

C

C

H

H

H

H

H

E

C

Electrophilic Aromatic Substitution in Aniline

C

C

C

C

C

H

H

H

H

H

E

C

Electrophilic Aromatic Substitution in Aniline

C

C

C

C

H

H

H

H

H

E

C

C

Electrophilic Aromatic Substitution in Aniline

C

C

C

C

H

H

H

H

H

E

C

C

Electrophilic Aromatic Substitution in Aniline

C

C

C

C

H

H

H

H

E

C

C

Electrophilic Aromatic Substitution in Aniline

C

C

C

C

H

H

H

H

E

C

C

Electrophilic Aromatic Substitution in Aniline

C

C

C

C

H

H

H

H

E

C

C

Electrophilic Aromatic Substitution in Aniline

Bromination

Aniline

2,4,6-Tribromoaniline

Too reactive towards electrophilic substitution reaction

p-Bromoaniline

Mono brominated product

o-Bromoaniline

Mono-bromination of Aniline

Pyridine

p-Bromoaniline

Too reactive towards electrophilic substitution reaction

12C13.3

​

PSV 1

Q.

Sol.

Pyridine

Too reactive towards electrophilic substitution reaction

Activating effect will decrease

12C13.3

​

CV 2

​

Nitration and Sulphonation

Nitration

Aniline

Nitroaniline

Protonated nitric acid

Nitronium ion

Acid

Base

Electrophile

Generation of electrophile

Nitration

o-Nitroaniline

m-Nitroaniline

p-Nitroaniline

2 %

47 %

51 %

-o and –p directing

High yield of m-Nitrophenol

Aniline

Nitration

Aniline

Anilinium ion

m-directing

Nitration

m-Nitroaniline

47 %

p-Nitroaniline – Major product

Pyridine

Too reactive towards electrophilic substitution reaction

p-Nitroaniline

Sulphonation

Aniline

Anilinium hydrogensulphate

453 – 473 K

Sulphanilic acid

Zwitter ion

12C13.3

​

PSV 2

Q.

Aniline does not undergo Friedel-Crafts reaction. Why ?

Sol.

Lewis acid

Aniline

Alkyl halide

Salt

Strong deactivating group

No Friedel-Crafts reaction

Summary

Bromination

Nitration

Sulphonation

Reference Questions

NCERT Exercise Questions: 13.3 (iv), (v), 13.11 (v)

Workbook Question: 7, 12, 17 (i),

12C13.3 Electrophilic Substitution Reaction of Amines

12C13.4��Diazonium salt

Learning Objectives

​

Introduction and preparation of diazonium salt

​

Properties of diazonium salt

​

12C13.4 Diazonium salt

12C13.4

​

CV 1

​

Introduction and preparation

of Diazonium salt

Introduction

Nomenclature of Diazonium salt

Parent Hydrocabron

(alkyl or aryl)

Diazonium

Cl^-,Br^-, HSO₄^-, BF₄^-

Benzenediazoniumchloride

Benzenediazoniumhydrogensulphate

Name of parent hydrocarbon + Diazonium + Name of anion

Introduction

Alkyldiazoniumsalt

Highly unstable

Arenediazoniumsalt

Stable at low temp. (273-278K)

Due to resonance

Method of preparation of Diazonium salt

Aniline

Benzenediazoniumchloride

Diazotisation

Mechanism

Electrophile

Formation of electrophile

Mechanism

Formation of Benzene diazonium salt

Aniline

Mechanism

Formation of Benzene diazonium salt

or

or

12C13.4

​

CV 2

​

Properties of Diazonium salt

​

Physical properties

1. colorless crystalline solid

2. Readily soluble in water

3. Stable in cold water

Chemical reaction

Divided in two categories

Reactions involving

displacement of N₂

Reactions involving

retention of diazo group

N₂ gas escape

N₂ group retain

Reactions involving displacement of Nitrogen

1. Sandmeyer reaction

Benzenediazoniumchloride

Chlorobenzene

Bromobenzene

Cyanobenzene

This method is not used to prepare iodobenzene and fluorobenzene

2. Gatterman reaction

Reactions involving displacement of Nitrogen

Benzenediazoniumchloride

Chlorobenzene

Bromobenzene

3. Formation of Iodobenzene

4. Formation of Fluorobenzene

Reactions involving displacement of Nitrogen

Benzenediazoniumchloride

Benzenediazoniumchloride

Iodobenzene

Fluorobenzene

5. Formation of Benzene