Chapter 23, Problem 23.29P

Interpretation Introduction

Interpretation:

Comparing to diphenylamine $\left({\text{pK}}_{\text{a}}\text{= 0}\text{.79}\right)$, aniline $\left({\text{conjugate acid pK}}_{\text{a}}\text{ = 4}\text{.63}\right)$ is a stronger base. Reason for this difference has to be marked.

Concept introduction:

Amines are the derivatives of ammonia $\left(N{H}_3\right)$ with one or more of the hydrogens replaced with a substituent such as an alkyl group.

Depending on the number of carbon side chain of the nitrogen, different types of amines can form.

If nitrogen atom of amine group is attached only to alkyl groups, then it is an aliphatic amine.

If nitrogen atom of amine group is attached to at least one aryl groups, then it is an aromatic amine.

Lone pair present on nitrogen of aromatic amine takes part in resonance by interacting with the $\pi$ system of the aromatic ring. This stabilizing interaction will be lost when the aromatic amine is protonated. Therefore, aliphatic amine is more basic than comparing to an aromatic amine.