1.3- Dithiane, mass spectra

The ratio of peak heights for HDS and H2S loss from 3, 3-d2- and 4, 4-d2-pentane thiols was found to differ in 12 eV El mass spectra compared with 70eV spectra [256]. An intramolecular isotope effect of 1.2 was observed in the loss of C3H7S2 in the El mass spectrum of bis-1, 3-dithiane specifically labelled with deuterium on one of the tertiary carbon atoms [762]. 

From the El mass spectrum, an intramolecular secondary isotope effect of 1.1 was obtained for the a-cleavage reaction in the molecular ion of monodeutero bis-1, 3-dithiane [762]. 

In contrast to 31, its dithio-analogue ethenedithione, S=C=C=S (32), is a very stable molecule when produced by collisional reduction of its cation-radical, which is formed abundantly by dissociative ionization of 1,3,4,6-tetrathiapenta-lene-2,5-dione (Scheme 10). The high stability of 32 is documented by the fact that following reionization 32+ represents the dominating base peak of the +NR+ mass spectrum [121]. Molecule 32 was subsequently generated by flash-vacuum pyrolysis of l,3-dithiane-2-cyclopentylideneketene and characterized by mass spectrometry [122]. 

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