Amines

=__**Amines**__=

Amines are thought of as derivatives of ammonia in which one or more of the hydrogen atoms in the ammonia molecule have been replaced by alkyl or aryl groups

Ammonia: A Primary Amine: A Secondary Amine:



Amines are very reactive compounds, so they are useful as intermediates in synthesis

We use the terms 'primary', 'secondary' and 'tertiary' for amines slightly differently from the way we do with alcohols. In amines it refers to the number of substituents on the //nitrogen// atom.

__How to name amines__

 * Primary Amines have the general formula RNH2, where the R can be an alkyl or aryl group. Amines are named usin the suffix -amine, for example:

CH3 -- NH2 is methylamine

C2H5 -- NH2 is ethylamine


 * Secondary Amines have the general formula RR'NH, for example:

(CH3)2NH is dimethylamine

(C2H5)3N is triethylamine Different substituents are written in alphabetical order, for example: Ch3(C3H7)NH is methylpropylamine
 * Tertiary Amines have the general formula RR'R''N, for example:

__﻿The properties of primary amines__
__Shape__ Ammonia is a pyramidal molecule with bond angles of approximately 107degrees. The difference is caused by the lone pair which repels more than the bonding pairs of electrons in the N-H bonds. Amines keep this basic shape

__Boiling Points__ Amines are polar

= __ Amines as nucleophiles and their synthesis __ =

The lone pair of electrons from an amine will attack positively charged carbon atoms. So, amines, like ammonia, will act as nucleophiles.

Primary aliphatic amines are produced when haloalkanes are reacted with ammonia. There is nucleophilic substitution of the halide by NH2. NH3 + RX [RNH3]+X- [RNH3]+X- + NH3 RNH2 + [NH4]+X-
 * __ Reactions of ammonia with haloalkanes __

However, the primary amine produced is also a nucleophile and this will react with the haloalkane to produce a secondary amine: RNH2 + RX [R2NH2]+X- [R2NH2]+X- + NH3 R2NH + [NH4]+X-

The secondary amine will react to give a tertiary amine: R2NH + RX [R3NH]+X- [R3NH]+X- + NH3 R3N + [NH4]+X-

and this in turn will react to produce a quaternary ammonium salt: R3N + RX [R4N]+X-

So a mixture of primary, secondary and tertiary amines and a quaternary ammonium salt is produced. This means that this is not a very efficient way of preparing an amine, though the products may be separated by fractional distillation. A large excess of ammonia gives a better yield of primary amine.