Chapter 25, Problem 25.5P

Interpretation Introduction

Interpretation:

A plot similar to that in Figure $\text{25-3}$ is to be drawn for relative stabilities of the ethyl radical (${\text{CH}}_{\text{3}}{\text{-CH}}_{\text{2}}\text{•}$) and the allyl radical.

Concept introduction:

The breaking of a covalent bond, whereby the electrons making up that bond are distributed equally to the atoms which are disconnected is known as the homolytic bond dissociation or homolysis. So in homolysis generally radicals are formed. In homolysis, a covalent bond is a breakdown equally and each atom acquires a single electron which is called a radical and a single barbed arrow () is used to represents the movement of a single electron in a homolysis process. In homolysis, the radicals from a breaking of the weakest bond of the molecule give the major products. The weakest bond possesses the smallest bond dissociation energy. The stability order for radicals is ${\text{methyl radical < 1}}^{\text{o}}{\text{radical < 2}}^{\text{o}}{\text{radical < allylic radical < 3}}^{\text{o}}\text{radical}\text{.}$ The more stable radical is always in its lowest energy state. Since radicals are electron-poor like carbocation the electron-donating groups increase the stability of radicals.