105907-74-2Relevant articles and documents
Aromatic Substitution in the Gas Phase. Alkylation of Arenes by C4H9+ Ions from the Protonation of C4 Alkenes and Cycloalkanes with Gaseous Bronsted Acids
Cacace, Fulvio,Ciranni, Giovanna,Giacomello, Pierluigi
, p. 1373 - 1378 (2007/10/02)
Use of a reactive aromatic substrate (o-xylene) to sample the isomeric population of the butyl ions from the gas-phase protonation of the C4H8 hydrocarbons shows that the primary product from linear olefins and methylcyclopropane is the s-butyl ion, or at least an s-butylating charged species displaying a positional selectivity very similar to that measured for the thermal s-butyl cations obtained from n-butane.A fraction of the primary C4H9+ ions isomerizes to the most stable tertiary structure, to an extent which depends, inter alia, on the exothermicity of the proton transfer process.Protonation of cyclobutane gives an alkylating reagent whose s-butylation/t-butylation ratio and positional selectivity set it apart from the C4H9+ reagents obtained from the other C4H8 hydrocarbons, suggesting the intervention of a different electrophile, conceivably protonated cyclobutane.Finally, protonation of isobutene yields exclusively a t-butyl ion that does not isomerize despite the large exothermicity of its formation.
