Question

Question: Explain why ${\mathbf{CH}}_{\mathbf{3}}{\mathbf{CONH}}_{\mathbf{2}}$ is a stronger acid and a weaker base than ${\mathbf{CH}}_{\mathbf{3}}{\mathbf{CH}}_{\mathbf{2}}{\mathbf{NH}}_{\mathbf{2}}$ .

Short answer

Answer

The given amide ${\mathrm{CH}}_3{\mathrm{CONH}}_2$is a stronger acid and a weaker base than ${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{NH}}_2$ as the lone pair is not available for donation.

Step-by-step solution

Step-by-Step SolutionStep 1: Reaction of amides

Amides possess the least reactivity among carboxylic acids as they consist of a poor leaving group. They get subjected to hydrolysis in acidic or basic conditions to generate carboxylic acid and carboxylate anions.

Reaction of amines

Amines are regarded as reactive because of the variation in electronegativity of hydrogen and nitrogen. The lone electron pair on nitrogen also tends to become reactive.

Reasons why  CH3CONH2 is a stronger acid and a weaker base than   CH3CH2NH2

The resonance structures of ${\mathrm{CH}}_3{\mathrm{CONH}}_2$ make the conjugate base more stable, and ${\mathrm{CH}}_3{\mathrm{CONH}}_2$is hence regarded as a strong acid.

Resonance structures of ${\mathrm{CH}}_3{\mathrm{CONH}}_2$

The reaction of ${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{NH}}_2$as an acid can be given as:

Here there is no resonance stabilization of the conjugate base.

The reaction of ${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{NH}}_2$ as a base can be given as:

Reaction of ${\mathrm{CH}}_3{\mathrm{CONH}}_2$as a base

In the case of ${\mathrm{CH}}_3{\mathrm{CONH}}_2$, the electron pair is delocalized by resonance. This makes them less available for electron donation. Hence ${\mathrm{CH}}_3{\mathrm{CONH}}_2$is a much weaker base thanrole="math" localid="1649141897310" ${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{NH}}_2$ , as in ${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{NH}}_2$ the electron pair on the nitrogen atom is localized.