Neutralization-reionization and ab initio study of the CH2CHSOH ⇄ CH3CHSO rearrangement

Ethenesulfenic acid and ethanethial-S-oxide cation radicals (1+ and 2+ ) and molecules (1 and 2) were generated in the gas phase and their collisionally activated isomerizations were studied by tandem and neutralization-reionization (NR) mass spectrometry, and by ab initio quantum chemical calculations. Consistent with experiments, ion 1+ is calculated to be more stable than 2+ (ΔE = −96 kJ mol−1), while a reverse order of stabilities is found for the molecules 1 and 2 (ΔE = 12 kJ mol−1). Significant energy barriers are calculated for the isomerization of 1+ to 2+ (186 kJ mol−1) and 1 to 2 (137 kJ mole−1). NR spectra were also utilized to analyze mixtures of 1 and 2 produced by flash-vacuum pyrolysis of vinyl tert-butyl sulfoxide. Thiirane-S-oxide cation radical and its ring-opened distonic isomer, .CH2CH2SO+, are also found as stable structures giving characteristic collisionally activated dissociation and neutralization-reionization spectra.