Amine Properties

Physical Properties of Amine

1. Physical state of Amine

Lower amines are gases while higher members are mostly liquids. Amines are almost unpleasant, having fishy smell. In the pure state amines are colourless, but in certain case they become coloured due to oxidation and mixing of impurities.

2. Boiling point

In amines, there are polar N-H bonds. Hence, in general they are polar. More over, in amines, inter molecular hydrogen bonds are present, leading to high boiling points in comparison to corresponding hydrocarbons of the same molar mass.

Primary and secondary amines can form hydrogen bonding hence they higher boiling points than isomeric tertiary amines.

3. Solubility in water

All the three classes of amines can form hydrogen bond with water. Hence they are soluble in water. But higher amines are least soluble due to the non-polar effect of big alkyl groups. Due to weaker hydrogen bonds solubility of amines in water is less than that of alcohols.

Carbylamine Reaction - Test for Amines

Distinction between primary, secondary and tertiary amine Using Carbylamine Reaction

Primary amine (both aliphatic and aromatic) when warmed with chloroform and alcoholic KOH, gives isocyanides (carbylamines). This is called carbylamine reaction. Carbylamines has an offensive smell. This reaction is answered only by primary amine and hence to distinguish primary amine from other classes of amines.

In general

R-NH2  +  CHCl3  +  3KOH  --------->  RNC (carbylamine) +  3KCl + 3H2O