FRAGMENTATION OF ORGANOSULFUR COMPOUNDS UPON ELECTRON-IMPACT .3. METASTABLE DECOMPOSITION OF THE MOLECULAR-IONS OF METHYL THIOGLYCOLATE ANDETHYL THIOGLYCOLATE

The metastable decompositions of the molecular ions of methyl thioglyc olate (1) and ethyl thioglycolate (2) were investigated by means of ma ss analyzed ion kinetic energy (MIKE) spectra and deuterium labeling. The loss of methanol is the only metastable decomposition of 1(+.). Th is 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 C2H3O2. All of these decompositions, except the loss of e thene, occur through two distinct mechanisms. During the loss of C2H3O 2, the ethyl group or ethene migrates from the oxygen to the sulfur at om. The loss of HCS, which corresponds to the loss of HCO with a conco mitant double hydrogen transfer observed in the case of methyl glycola te (3), does not participate in the metastable decomposition of 1(+.) and 2(+.). This is due to the energetic favorableness of the loss of m ethanol. (C) 1997 American Society for Mass Spectrometry.