Protonation-induced isomerization of gaseous bromoxylenes: a radiolytic and mass spectrometric study

Abstract

The isomerization of bromoxylenes following protonation by X₃⁺(X = H or D), C_nH₅⁺(n= 1 or 2), iso-C₃H₇⁺, and t-C₄H₉⁺ ions in the dilute gas state has been investigated. Further evidence has been derived from chemical ionization mass spectrometry and related radiolytic experiments concerning methylation of bromotoluenes by gaseous (CH₃)₂F⁺ ions. The results suggest that the observed intra-molecular Br migration involves the intermediacy of a radical cation–bromine atom pair. The mechanistic relevance of the results to gas-phase aromatic substitution by free bromine cation is discussed.