Question

The reaction of a nitrile with an alcohol in the presence of a strong acid forms an N-substituted amide. This reaction, known as the Ritter reaction, does not work with primary alcohols.

a. Propose a mechanism for the Ritter reaction.

b. Why does the Ritter reaction not work with primary alcohols?

c. How does the Ritter reaction differ from the acid-catalyzed hydrolysis of a nitrile to form an amide?

Short answer

a.

b. The Ritter reaction does not work for primary alcohol as it does not form a carbocation.

c. The difference in the two reactions is the electrophile that connects to the nitrogen of the nitrile.

Step-by-step solution

Step-by-step-solutionStep 1: Reaction of nitriles

Nitriles are difficult to be hydrolyzed than amides. But they hydrolyze slowly resulting in a carboxylic acid when heated with water and an acid. The catalytic hydrogenation of nitrile leads to the formation of primary amine.

Proposed mechanism for the Ritter reaction

a. The mechanism is shown below:

Mechanism for the Ritter reaction

The Ritter reaction is a well known reaction in organic chemistry that is used for the generation of amide by combining a nitrile and a carbocation precursor like a substituted alkene or secondary or tertiary alcohol.

b. The Ritter reaction does not work for primary alcohol as it does not form a carbocation.

c. The difference in the two reactions is the electrophile that connects to the nitrogen of the nitrile. It is a carbocation in the Ritter reaction and a proton in the acid-catalyzed hydrolysis of nitrile.