Radical‐induced aromatic substitution between benzoyl peroxide and benzenediols in the gas phase characterized by mass spectrometry

Abstract

A radical-induced aromatic substitution mechanism for the reaction between benzoyl peroxide and benzenediols in the gas phase was characterized by mass spectrometry. The benzoyloxy radical produced from the hornolysis of benzoyl peroxide associates at its carbonyl group with the phenolic hydroxyl group. The pairing tendency of the unpaired electron on the oxygen of the radical induces electron transfer along the hydrogen bond, which results in the rupture of the 0-H bond of the phenol and aromatic substitution at the ortho position of the benzoyloxy radical. Supporting evidence for the mechanism was obtained by isotope labelling.

Ion−Radical Complexes and SRN1-like Reactions in the Gas-Phase. A Negative-Ion Mass Spectrometric Investigation of Arylazo Sulfides

“…Moreover, the hypothetical formation of ArSR •- by coupling between an Ar • radical and a RS - anion as separated species ensuing from (i) unimolecular fragmentation of ArNNSR •- or (ii) two different molecules of azo sulfide, is very unlikely in the ion source of a mass spectrometer. Actually, only few reactions of this kind between ions and radicals have been reported; − furthermore, such a reaction should be very sensitive to the concentration of substrate in the ion source, while the fragmentation described here shows no dependence upon the quantity of sample introduced 1 …”

“…Radical molecule reactions have been observed for example between 7,7,8,8-tetracyanoquinodimethane and the CH 3 . radicals obtained from the reagent gas 27,28 and between benzoyl radicals and benzene-1,4-diol . However in this last case, the radicals are produced by thermal decomposition of benzoyl peroxide during the coevaporation of both reagents.…”