Question

The alkyl cyanides are
A. Acidic
B. Basic
C. Neutral
D. Amphoteric

Answer 1

Hint: When the H atom of HCN is substituted by an alkyl group or aryl group, a cyanide compound is formed. Alkyl cyanide or alkyl nitrile is very much unstable in water. The nature of alkyl cyanide depends upon the nature of the product upon hydrolysis in acidic or basic aqueous solutions.

Complete step by step solution:
Alkyl cyanide groups have a cyanide functional group ($-CN$ group) and are formed when alkyl halide
(R-X) reacts with metal cyanide ( NaCN, KCN, etc.).

Alkyl cyanides are very unstable in water and undergo rapid hydrolysis both in acidic or basic medium.

In acidic medium: When alkyl cyanide (R-CN) is heated under reflux with dilute acid for example dilute hydrochloric acid, a carboxylic acid (R-COOH) is formed. In the acidic medium, alkyl cyanide acts as an electrophile and activates the C-N triple bond for a nucleophilic attack of water forming an amide as an intermediate, which is then further hydrolyzed to carboxylic acid as the major product.

In basic medium: In a basic medium, when alkyl cyanide is heated under reflux with base, sodium hydroxide (NaOH) carboxylic acid salt of sodium is formed. At first nucleophilic addition of the hydroxide ion to the C-N triple bond occurs forming an amide intermediate.

These chemical properties are the reason to consider alkyl nitriles to be acid derivatives.
Thus option (A) is correct.

Note: Cyanide and isocyanide both are functional isomers of each other and they can be synthesized from hydrocyanic acid (HCN). In isocyanides (R-NC) alkyl or aryl groups are attached to the nitrogen atom of the –CN group and for cyanides (R-CN), they are attached to a carbon atom of the –CN group. Isocyanides are only hydrolyzed by dilute acids to give formic acid and a primary amine.