Question

Write the mechanism of carbylamine reaction.

Answer 1

The carbylamine reaction also known as Hoffman isocyanide synthesis is a reaction carried out with primary amine, chloroform and a base .Here dichlorocarbene is formed as an intermediate.

Complete step by step answer:
We have studied the basic concepts of organic chemistry which tells us about the named reactions and some of the related reactions along with the mechanism of that reaction.
We shall now see the mechanism of the carbylamine reaction and approach to the correct answer.
- We know that carbylamine reaction involve reaction of a primary amine with base and chloroform to form alkyl/aryl isocyanide
- The mechanism proceeds in the following way that the lone pair of electrons on nitrogen of aniline which attacks the intermediate carbine formed which then reacts with base and forms a product which is then followed by the treatment of base again to give the desired product that is iso cyanide.
- The mechanism taking place is as given below:

- It involves the addition of amine to the intermediate created from the dehydrohalogenation of chloroform. This intermediate is called dichlorocarbene.
- The electrophilic dichlorocarbene attacks the nucleophilic nitrogen of the primary amine. The elimination of hydrochloric acid leads to formation of isonitrile.
- The products formed are alkyl isonitrile, potassium chloride and water.

Note: Note that this carbylamine reaction is used as a standard test for identification of primary amines. It is used to synthesize isocyanides from primary amines with the help of chloroform and a base.