Two Routes in the Formation of Hydrogen Halides from OH Adducts of Halogenated Anisoles in Aqueous Solution

Abstract

AbstractUsing pulse radiolysis with conductivity detection and steady state γ‐radiolysis it is shown that in aqueous solution the reaction of OH radicals with 2,3‐ and 4‐monohalo (X = F, Cl, Br) anisoles leads to the production of hydrogen halides (HX). The G‐values for production of hydrogen halides measured 10 μs after the pulse are large for the 2‐ and 4‐haloanisoles (G(HX) = 0.5‐1.45) and small for the 3‐haloanisoles (G(HX) = 0.1‐0.3). These yields reflect the amount of OH addition to ring positions substituted by X. The differences in these amounts reflect an ortho‐para directing activity of the methoxy group. – In the case of the OH adducts of 3‐haloanisoles – in contrast to those of 2‐ and 4‐haloanisoles – in addition to the prompt a second order elimination of HX is observed which occurs on the ms time‐scale. This shows that the distribution of OH addition cannot always be obtained from product studies using γ‐radiolysis. The G(HX) values measured using steady state γ‐radiolysis agree with those determined in the ms range using pulse radiolysis.