Electron impact induced ortho effects in 2-nitro-substituted aromatic sulphides containing 2-pyridyl, 2-(5-methylthio-1,3,4-thiadiazolyl) and/or 2-(4-methyl-1,3,4-thiadiazolinyl-5-thione) moieties

The most significant mass spectral features of 14 title compounds are discussed with the aid of deuterium labelling experiments. The decomposition patterns of these compounds are strongly affected by several competing ortho effects, due to the interaction of the nitro function(s) with neighbouring electron-poor N-heterocycles. Very intense polycyclic ions are produced via addition-elimination reactions by loss of simple radicals Hsup(radical), OHsup(radicals), NO2sup(radical) from the molecular ion, followed by the ejection of neutral molecules (HNO2, CH3SCN or CH3NCS). In addition, primary or secondary intramolecular oxygen transfers, preceded or not by hydrogen migration, from the nitro group to the amino carbon via spirocyclic intermediates, are generally observed. Minor skeletal rearrangements, triggered by single or multiple intramolecular oxygen transfer to the bridgehead sulphur atom, followed by SO or SO2 ejection, are also noticed. (author)