Electron bombardment induced fragmentation of substituted oxathiolanes

The mass spectral fragmentation patterns of 1,3‐oxathiolane and 2‐, 4‐, and 5‐substituted oxathiolanes have been recorded. The various fragments have been identified by high‐resolution mass spectrometry when appropriate. Of the five possible modes of ring cleavage to produce two‐ and three‐atom fragments only two modes are actually observed. The mode of fragmentation of the 1,3‐oxathiolane ring differs from that proposed for 1,3‐dioxalane and in all probability occurs in multistep processes.