Gas-Phase Acid-Induced Nucleophilic Displacement Reactions. 8. Structural Analysis of Intermediate Ions Formed by the Decomposition of β-Arylethyl Onium Ions

Article abstract of DOI:10.1021/ja00209a006

The existence of the stable unsubstituted ethylenebenzenium ion 3 as a stable gaseous species is inferred as occuring in the reaction pathway induced by the attack of radiolytically formed gaseous acids GA⁺ (GA⁺ = D3⁺, CnH5⁺ (n = 1,2), and CH3FCH3⁺) on β-phenyl-Y-ethanes (Y = F, Cl, and OH).Neutral product analysis allows use to define the detailed reaction mechanism and to extend previous conclusions concerning adjacent phenyl group participation in the nucleophilic displacement process, which take place in competition with 1,2-H migration.Occurence of alternative cyclic structures, e.g. 7, in the participation step is ruled out on the grounds of results of specifically designed radiolytic expriments.The mechanistic picture that caracterizes neighboring phenyl-group participation in cationic nucleophilic substitutions occuring in the gas phase presents interesting analogies with related processes occuring under solvolytic conditions and in superacidic media.The results from the present gas-phase radiolytic approach are discussed and contrasted with pertinent mass spectrometric data and theoretical predictions.