Amines

Lesson

Part 1 — organic relatives of ammonia: what they are, how they are made and why they are bases.

In this lesson you will

Classify and name amines and describe the structure of the amino group
Write preparations of amines by reduction, ammonolysis, Gabriel phthalimide synthesis and Hoffmann bromamide degradation
Explain the physical properties of amines
Compare the basic strength of aliphatic and aromatic amines using inductive, solvation, steric and resonance effects

Table of familiar amines and where they are met
Compound	Where you meet it
Trimethylamine	Smell of fish
Putrescine, cadaverine	Smell of decaying matter
Adrenaline (an amine)	Hormone of the fight-or-flight response
Aniline	Starting material for dyes and drugs
Novocaine (procaine)	Local anaesthetic

Concept

Classification and naming

Replacing one, two or three H of NH₃ gives primary (RNH₂), secondary (R₂NH) and tertiary (R₃N) amines. IUPAC names: alkanamine (ethanamine), with N- for groups on nitrogen (N-methylethanamine, N,N-dimethylmethanamine). Aryl amines are named as benzenamines (aniline = benzenamine).

Table of amines with their class and IUPAC name
Structure	Class	IUPAC name
$\ce{CH3CH2NH2}$	Primary	Ethanamine
$\ce{CH3NHCH2CH3}$	Secondary	N-Methylethanamine
$\ce{(CH3)3N}$	Tertiary	N,N-Dimethylmethanamine
$\ce{H2NCH2CH2NH2}$	Primary (diamine)	Ethane-1,2-diamine
$\ce{C6H5NH2}$	Primary aryl	Benzenamine (aniline)
$\ce{C6H5N(CH3)2}$	Tertiary	N,N-Dimethylbenzenamine

Diagram

Structure of amines

Nitrogen is sp³ hybridised: three σ bonds and a lone pair give a pyramidal shape; the C–N–C angle (about 108°) is a little less than tetrahedral. In aniline the lone pair is partly delocalised into the ring.

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