COLLISIONAL ACTIVATION AND METASTABLE ION CHARACTERISTICS .65. COLLISIONAL ACTIVATION AND THEORETICAL STUDIES OF GASEOUS CSH3+ IONS

Collisional activation mass spectra of m/z 47 ions from a variety of sulfur-containing compounds demonstrate that both the protonated thioformaldehyde, H2C=SH+ (a), and thiomethoxy, H3C-S+ (b), ion structures are stable (lifetimes > 10-5 s). Formation of a occurs by γ cleavage from thiols, as well as by low-energy anchimeric cleavage from methyl sulfides and by rearrangement of b at higher energies from methyl sulfides. The more stable isomer is indicated by CA to be a, in contrast to previously published thermochemical data. Ab initio calculations indicate that b is a triplet ion; empirical corrections allowing for neglect of correlation are necessary to give heat of formation values of a and b (205 and 215 kcal/mol, respectively) consistent with the experimental results. The activation energy for the rearrangement b → a is substantial (~40 kcal/mol). © 1979, American Chemical Society. All rights reserved.