Cyclization of dimethyl oxalate upon electron impact

✍ Scribed by J. G. Liehr; E. A. Larka; J. H. Beynon

• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: English
• Weight: 311 KB
• Volume: 16
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/oms.1210160110

✦ Synopsis

Abstract

Isotope labelling experiments and also consecutive fragmentation investigations of metastable ions, a novel technique in mechanistic studies, have been carried out to elucidate structure and genesis of the m/z 45 ions from dimethyl oxalate as well as dimethyl carbonate. It is shown that the formation of the m/z 45 ions, \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm{CH}}_{\rm{3}} \mathop {\rm{O}}\limits^{\rm{ + }} = {\rm{CH}}_{\rm{2}} $\end{document}, in the mass spectra of these compounds arises via single step processes. Mechanisms involving hydrogen transfer and subsequent formation of cyclic intermediates which then collapse to give \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm{CH}}_{\rm{3}} \mathop {\rm{O}}\limits^{\rm{ + }} = {\rm{CH}}_{\rm{2}} $\end{document} directly from molecular ions are suggested. No evidence was found for a two‐step fragmentation route to m/z 45 from the molecular ions of either dimethyl oxalate or dimethyl carbonate.