Chapter 9, Problem 9.14P

Interpretation Introduction

Interpretation:

For a given pair of leaving groups, ${\text{HCO}}_{\text{2}}{}^{\text{-}}$ and ${\text{C}}_{\text{6}}{\text{H}}_{\text{5}}{\text{O}}^{\text{-}}$, it is to be determined which one is a better leaving group.

Concept introduction:

Leaving groups are often negatively charged species, anions. How well the anion can stabilize the charge determines its stability and, in turn, its ability as a leaving group. Higher the stability of leaving group, the better its ability as a leaving group. Good leaving groups are stable anions and therefore weak bases.

The stability and therefore the ability of leaving groups can be determined on the basis of the pKa values of their conjugate acids. Lower the pKa value of the conjugate acid of the leaving group, better it is.