Free Chemistry NEET Notes for Amines

Free Chemistry Notes for Amines (NEET)

Power up your NEET Exam prep with Chapter-Wise Chemistry Notes for Amines at Onlineneetcoaching.in. Crafted by Brilliant Tutorial experts with 25 years of NEET insights.

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Important Chemistry Notes for IITJEE/NEET Preparation- Amines

Class 12 Chemistry is a broad subject that requires a thorough understanding of the concepts and topics covered. As a result, we have provided Chemistry Notes PDF for IIT JEE/NEET to students and NEET aspirants. Amines Class 12 Notes PDF for NEET can be found below. With the help of detailed syllabus, Class 12 students learn what they need to study, how many points are assigned to each unit, and how much time is allotted for each unit. As a result, they can easily plan their study schedule.

Check out the Amines Class 12 notes PDF for your IIT JEE/NEET Preparation based on the IIT JEE/NEET Chemistry Syllabus. The Amines notes PDF is designed in such a way that it is very useful for IIT JEE/NEET aspirants.

AMINES

Amines are derivatives of ammonia (NH3) in which one or more hydrogen atoms have been replaced by alkyl groups.

CLASSIFICATION

Amines are classified as primary (1º), secondary (2º) or tertiary (3º) according to the number of alkyl groups attached to the nitrogen atom

neet chemistry notes for amines class 12

The carbon atom of alkyl groups to which nitrogen is attached may be 1º, 2º or 3º but amine is always 1º, 2º or 3º if it has the grouping –

eg.

STRUCTURE

The nitrogen atom in amine is sp3 hybridised. The three hybrid atomic orbitals are involved in bond formation and one hybrid atomic orbital contains the unshared pair of electrons, giving the pyramidal structure to amine.

The bond angles are approximately tetrahedral

NOMENCLATURE

ISOMERISM

Amines exhibit following types of Isomerism

Chain Isomerism

Functional Isomerism

Position Isomerism

Metamerism

METHODS OF PREPARATION

These methods yielding mixture of amines

HOFMANN’S METHOD (Ammonolysis of alkyl halide)
Using aqueous or alcoholic NH3

When NH3 is in excess, 1º amine is the main product

When RX is in excess, 3º amine is the main product

SABATIER METHOD (Ammonolysis of alcohols)

When NH3 is in excess, 1º amine is main product.

SEPARATION OF AMINE MIXTURE

HINSBERG’S METHOD
Reagent used is Benzenesulfonyl chloride (C6H5SO2Cl) which has been replaced by
p-toluenesulfonyl chloride, CH3C6H4.SO2Cl

HOFMANN’S METHOD

Reagent used is Diethyl oxalate

METHODS GIVING PRIMARY AMINES ONLY

Reduction of nitro compounds by Sn/HCl, H2/Ni, Zn/HCl or LiAlH4

Reduction of cyanides (Mendius reaction)

Reduction of oximes : or LiAlH4 are reducing agents

+ H2O

Reduction of amide

Hoffmann's bromamide reaction: R can be alkyl or aryl (Conversion of an amide to 1º amine)

Gabriel’s phthalimide reaction

This method is not suitable for 1ºarylamine due to less nucleophilic character.

From 𝛂-amino acids

Reductive amination of Aldehydes and Ketones

From Chloramine and Grignard’s Reagent

Reduction of azide

Ritter reaction : for amines containing tertiary alkyl groups

By Lossen rearrangement : From Hydroxamic acid

Schmidt reaction

Curtius rearrangement

By Leuckart reaction

PREPARATION OF SECONDARY AMINES

From p-amines
From calcium cyanamide

Secondary amine containing phenyl group

From 1º-amine by the action of diazomethane

From aniline. It is one of the best methods

Reduction of isocyanides
(Mendius Reaction)
Reduction of N-Substituted amides

PREPARATION OF TERTIARY AMINES

By heating ethanolic solution of ammonia with excess of alkyl halide

Reduction of N, N-disubstituted amide

Decomposition of alkyl tetraammonium hydroxides

GENERAL PROPERTIES

Amines are soluble in water due to H-bonding. Lower members have fishy ammoniacal odour and are combustible gases. From C3 to C11 volatile liquids and from C12 are solids. The b.p. increases with increase in molecular weight.

Basic character : Amines are stronger bases than ammonia

⇌

The stability of ions by H–bonding in water follows the order

The order of basicity ought to be 1° > 2° > 3° which is practically not.

In fact it depends upon this factor

Inductive effect
Steric hindrance

Basic character follows the order
neet chemistry notes for amines class 12

Ammonia and amines oscillate between two structures as follows

Although the electron density on nitrogen is maximum (due to + I effect of alkyl groups) in case of tertiary amine but approach and bonding by proton is relatively difficult due to steric hindrance. The steric hindrance increases with the bulk of group and basic character decreases

Alkyl group Relative strength

Note : The order of basicity of amines in the gaseous phase is

tertiary amine > secondary amine > primary amine > ammonia

Aromatic amines are less basic than aliphatic amine. The electron withdrawing groups (-NO2, COOH, –CN, –SO3H) decrease the basic character and electron donating groups (–CH3; –OH) increase the basic character of aniline

Due to Resonance the lone pair of electrons is delocalised within benzene nucleus and not available for protonation and basic character is suppressed.

Amides are much less basic than amines due to Resonance.