The ortho:para ratio in aromatic nucleophilic substitution. Part I

Abstract

ortho:para Ratios have been measured for the reaction of o- and p-fluoro- and -chloro-nitrobenzenes with methoxide, ethoxide, and isopropoxide ions. The rates of substitution at the 2- and 4-positions of 2,4-difluoro- and 2,4-dichloro-1-nitrobenzenes by these anions have also been determined. The results are discussed in terms of steric exclusion of solvation in the transition states of the reactions, and for 2,4-dichloro-1-nitrobenzene, the effect of rotation of the nitro-group out of the plane of the benzene ring is examined.