Chapter 25, Problem 25.46P

Interpretation Introduction

Interpretation:

Whether the selectivity of radical chlorination at ${\text{1}}^{\text{o}}{\text{, 2}}^{\text{o}}{\text{, and 3}}^{\text{o}}$ carbons will increase or decrease when the reaction is carried out in benzene is to be explained.

Concept introduction:

Radical halogenation is sensitive to the type of carbon radical that is produced in the propagation step. The stability of carbon radicals changes as ${\text{1}}^{\text{o}}{\text{ < 2}}^{\text{o}}{\text{ < 3}}^{\text{o}}$. The probability of radical halogenations at these carbons also changes in the same order.

The selectivity also depends on the halogen being used. Selectivity increases as the enthalpy change of the overall reaction reduce, i.e., becomes less negative or more positive.