FRAGMENTATION OF ORGANOSULFUR COMPOUNDS UPON ELECTRON-IMPACT - 2-MERCAPTOETHANOL AND 1,2-ETHANEDITHIOL

The spontaneous unimolecular dissociations of 2-mercaptoethanol (1) an d 1,2-ethanedithiol (2) have been investigated by mass-analyzed ion ki netic energy (MIKE) spectra, collision-induced dissociation (CID) spec tra and deuterium labeling. Most of the fragmentation pathways of 1 an d 2 are similar to those of ethylene glycol (3), but there are excepti ons, The results are rationalized by thermochemical considerations. Pr otonated methanethiol (CH3SH2+; m/z 49) is produced from 1 and 2, and protonated methanol(CH3OH2+; m/z 33) is also generated from 1. The lat ter is a minor route in comparison with the case of 3. The m/z 49 ion contains both hydroxyl and mercapto hydrogens of 1(.+). The former is contained in the methyl group, and one of the beta-methylene hydrogens is bonded to the sulfur atom.