Chapter 18.12, Problem 14P

Interpretation Introduction

Interpretation:

An explanation for the higher reactivity of fluorobenzene than chlorobenzene toward electrophilic substitution reaction and higher reactivity of chloromethylbenzene than fluoromethylbenzene is to be stated.

Concept Introduction:

Halogens are weakly deactivating. They donate electrons to the benzene ring by resonance and withdraw electrons from the ring inductively. Fluorine uses a $\text{2p}$ orbital to donate its electrons by resonance. Chlorine, bromine and iodine are less effective at donating electrons by resonance because they use $\text{3p,}\text{4p}$ and $\text{5p}$ orbitals respectively. These orbitals do not overlap efficiently with $\text{2p}$ orbital of carbon.