CH 3CH 3+· formation from some C 3H 6O +· isomers according to theory

Abstract

Dissociations to alkane ions in gas phase ion chemistry are rare and poorly characterized. Therefore, the pathways to CH 3CH 3 +· + CO from ·CH 2CH 2O +CH 2 and some of its isomers are investigated by theory. The pathway found for this reaction is ·CH 2CH 2O +CH 2 → CH 3CH 2O +CH · → [CH 3CH 2 - - H - - CO] +· → CH 3CH 3 +· + CO. The crucial intermediate in this pathway is the stable hydrogen-bonded ion-neutral complex [CH 3CH 2 - - H - - CO] +·, a species held together by a strong hydrogen bond. CH 3CH 3 +· + CO rather than CH 3CH 3 + CO +· is formed from ·CH 2CH 2O +CH 2 and other C 3H 6O +· ions because the former pair is much more stable than the latter. The photoionization appearance energies of CH 3CH 3 +· from CH 3CH 2CHO +· and from CH 3CH 2CO 2H +· demonstrate that the onsets of these reactions are at to just above their thermochemical thresholds, consistent with the intermediacy of ion-neutral complexes. We also found transition states for interconversion of CH 3CH 2CHO +· and CH 3CH 2O +CH · and transformation of CH 3CH 2OH +· to CH 3CH 2CHO +·; the latter reaction occurs by a 1,2-H-shift from O to C.