Question

Rank the following amides from greatest reactivity to least reactivity toward acid-catalyzed hydrolysis:

Short answer

Amide shows avariety of chemical reactions. They are reactive due to the $\mathbf{-}\mathit{N}{\mathit{H}}_{\mathbf{2}}$group. As a result, different nucleophiles can be substituted in the amide.

Nucleophile substitution of hydroxide group in the amide occurs at ahigh temperature, resulting in carboxylic acid formation.

Step-by-step solution

Amide reactivity

Amide shows avariety of chemical reactions. They are reactive due to the $\mathbf{-}\mathit{N}{\mathit{H}}_{\mathbf{2}}$group. As a result, different nucleophiles can be substituted in the amide.

Nucleophile substitution of hydroxide group in the amide occurs at ahigh temperature, resulting in carboxylic acid formation.

Comparing amide reactivity

The relative reactivity of the given amides depends on the basicities of their leaving group; that is, the weaker the base, the more reactive the given amide.

• The given amide (A) on removing the leaving group cyclohexyl ammonium ion has the pKa value of 11.2.
• The given amide (B) on removing the leaving group anilinium ion has the pKa value of 4.58.
• The given amide (C) on removing the leaving group para-nitroanilinium ion has the pKa value of 0.98.

The lower the pKa value, the stronger the acidic, the weaker the conjugate base and the weaker the base better is the leaving group making it more reactive amide[S1] . Therefore, the reactivity order of amide is as follows.

Reactivity order of amide