2-Benzylindane radical cations in the gas phase (Part I): Substituent effects on a stereoselective McLafferty reaction and related hydrogen transfer processes

摘要: Abstract In the present and accompanying article, unimolecular fragmentation of radical cations 2-benzylindane eleven derivatives bearing meta- or para-substituents at benzylic moiety has been studied with a special focus on hydrogen exchange that precedes McLafferty reaction. Standard EI mass spectra, low-energy (11 eV) spectra mass-analyzed ion kinetic energy (MIKE) were recorded to probe excitation-energy ion-lifetime dependence exchange. Density-functional theory calculations used rationalize substituent effects competition between cleavage reaction clarify role distonic arenium ion-type intermediate formed by γ-hydrogen-transfer step The ipso-protonolysis benzyl residue giving rise loss substituted benzenes specifically from most para-isomers was also found reflect