Aromatic substitution in the gas phase. Part III. Reaction of the D2T+ ion with gaseous arenes. General remarks on the reactivity of gaseous Brønsted acids

Abstract

The results of a study of gas-phase triton transfer from D₂T⁺ to benzene and toluene are reported. The electrophile, prepared from the γ-radiolysis of gaseous D₂ containing a tracer activity of DT, was allowed to react with the aromatic substrate, in the presence of oxygen as a radical scavanger. The relative reactivity of the arenes towards the electrophile, and the distribution of the tritium atoms in the labelled toluene formed were determined. The results are compared with those obtained with a stronger gaseous Brønsted acid, the helium tritiide ion, and the mechanism of gas-phase electrophilic attack is discussed. It is suggested that a model based on the formation of an electrostatic complex between the electrophile and the aromatic substrate can account for the main features of the gas-phase tritiodeprotonation.