Chapter 3, Problem 62IP

Interpretation Introduction

Interpretation:

The drastic change in ${\text{pk}}_{\text{a}}$-value of amines in the presence of cyano group is needed to be explained and the more acidic ( ${\text{pk}}_{\text{a}}$ lower than 17) amines attached by a R group is needed to find out.

Concept introduction:

${\text{pk}}_{\text{a}}$-value of compound gives the strength of acidity of a compound. The lesser the value of ${\text{pk}}_{\text{a}}$ will have more acidic strength. Stability of conjugate base determines the strength of acid.

The conjugate base having resonance will have greater stability as compared to conjugate base having single anion. Because of the resonance, conjugate base will get resonance stabilization.

To Explain: the drastic change in ${\text{pk}}_{\text{a}}$-values of amines in presence of the cyano group.