Electron‐impact studies—XLVII: The mass spectra of 2‐aryl‐1,3‐dithianes and ‐1,3‐dithiolanes

The fragmentation patterns in the spectra of 2‐aryl‐1,3‐dithianes and ‐1,3‐dithiolanes have been elucidated by deuterium labelling studies. Ortho effects are observed in the spectra of 2(o‐alkoxyphenyl)‐1,3‐dithianes. The molecular ions of the 1,3‐dithianes eliminate S2H· and metastable kpeaks substantiate these eliminations. The hydrogen involved in this elimination randomises (C‐4, 5 and 6) Prior to elimination in the spectrum of 2‐phenyl‐1,3‐dithiane, but originates mainly from C‐5 in that of the bis propane‐1,3‐dithioacetal of terephthaldehyde.