Arylation of Dialkyl Ethers by Gaseous Phenylium Ions. Formation and Behavior of Dialkylphenyloxonium Ions in the Gas Phase

Reactions were studied of C6H4T+, obtained in the gas phase from the spontaneous decay of p-T2C6H4, with ROR1 (R = Me, R1 = Pr, CHMe2; R = Pr, R1 = CHMe2) at 20-400 Torr, and in the presence of the thermal radical scavenger O2 at 4 Torr. The effects of the base NH3(g) (4 Torr) on the reaction at the highest pressure were also studied. Singlet phenylium ion confirms its affinity toward the n-center of the substrate, although significant insertion into the alkyl groups of Me2CHOPr is also obsd. The stabilities and reactivities of the intermediate dialkylphenyloxonium ions were studied, together with fragmentation and isomerization mechanisms. The behavior of gaseous dialkylphenyloxonium ions at 20-400 Torr is consistent with previous mechanistic hypotheses from mass-spectrometric studies at much lower pressures (<1 Torr).