Question

If x and y are the pKb values of p-methylaniline and N,N-dimethylaniline, what is the relation between x and y?

(a) x > y

(b) x < y

(c) x = y

(d) x >> y

The question was asked in examination.

The origin of the question is Amines Chemical Reactions topic in chapter Amines of Chemistry – Class 12

Answer 1

The correct answer is (a) x > y

To explain: The basicity of N-methyl anilines is very slightly higher than that of ring substituted methyl anilines. This is because the methyl group is directly attached to the N atom in N,N-dimethylaniline and the electron effect is more pronounced. But this is only a minute effect.