Alkyl Isocyanides (Carbylamines)

Alkyl Isocyanides (Carbylamines)

Nomenclature of isocyanides

They are commonly named as Alkyl isocyanides. The IUPAC system names them as alkylcarbylamines

Table : Nomenclature of alkylisocyanides

Methods of preparation of isocyanides

1. From primary amines (carbylamines reaction)

Both aromatic as well as aliphatic amines on treatment with CHCl₃ in the presence of KOH give carbylamines

2. From alkyl halides

Ethyl bromide on heating with ethanolic solution of AgCN give ethyl isocyanide as major product and ethyl cyanide as minor product.

3. From N – alkyl formamide. By reaction with POCl₃ in pyridine.

Properties of isocyanides

Physics properties

• They are colourless, highly unpleasant smelling volatile liquids and are much more poisonous than the cyanides.

• They are only slightly soluble in water but are soluble in organic solvents.

• They are relatively less polar than alkyl cyanides. Thus, their melting point and boiling point are lower than cyanides.

Chemical properties

1. Hydrolysis: Alkyl isocyanides are not hydrolysed by alkalies. However they are hydrolysed with dilute mineral acids to give primary amines and formic acids.

2. Reduction: When reduced catalytically (or) by nascent hydrogen, they give secondary amines.

3. Isomerisation: When Alkyl isocyanides and heated at 250ºC, they change into the more stable, isomeric cyanides

4. Addition reaction. Alkyl isocyanides add on halogen, sulphur, and oxygen to form the corresponding addition compounds.