Fragmentation of organosulfur compounds upon electron impact. Part III. Metastable decomposition of the molecular ions of methyl thioglycolate and ethyl thioglycolate

The metastable decompositions of the molecular ions of methyl thioglycolate (1) and ethyl thioglycolate (2) were investigated by means of mass analyzed ion kinetic energy (MIKE) spectra and deuterium labeling. The loss of methanol is the only metastable decomposition of 1+.. This fragmentation occurs via two distinct pathways. The molecular ions of 2 decompose in a variety of ways, i.e., the losses of water, ethene, ethanol or Ċ2H3O2. All of these decompositions, except the loss of ethene, occur through two distinct mechanisms. During the loss of Ċ2H3O2, the ethyl group or ethene migrates from the oxygen to the sulfur atom. The loss of HĊS, which corresponds to the loss of HĊO with a concomitant double hydrogen transfer observed in the case of methyl glycolate (3), does not participate in the metastable decomposition of 1+. and 2+.. This is due to the energetic favorableness of the loss of methanol