Oxidation of Sulfur Compounds. II. Thermal Reactions of NO2 with Aliphatic Sulfur Compounds

Article abstract of DOI:10.1021/j150669a052

The reactions of NO2 with (CH3)2S, (CH3S)2, CH3SNO, and CH3SH were studied at 23 deg C in a Pyrex cell with a pinhole bleed to a mass spectrometer.In all cases reaction proceeded readily and NO was evolved.The (CH3)2S-NO2 reaction also produced (CH3)2SO.The CH3SH-NO2 reaction gave CH3SNO and (CH3S)2 as initial products, which in turn were further oxidized.The CH3SNO-NO2 reaction gave (CH3S)2 and (CH3SO)2, presumably with CH3S(O)NO formed as an undetected unstable intermediate.The (CH3S)2-NO2 reaction gave (CH3SO)2 as a primary product which further oxidized, presumably to give (CH3SO2)2.Undoubtedly (CH3S)2O and (CH3SO)2O were undetected intermediates leading to the formation of (CH3SO)2 and (CH3SO2)2, respectively.The indicated initial reactions are (CH3)2S + NO2 -> (CH3)2SO + NO (1), (CH3S)2 + NO2 -> (CH3S)2O + NO (3), CH3SNO + NO2 -> CH3S(O)NO + NO (7), CH3SH + NO2 -> CH3SNO + HO (12a).In addition another reaction may also occur: CH3SH + NO2 -> CH3S(O)H + NO (12c).The only reaction slow enough to measure was reaction 1 and it has a rate coefficient k₁ ca. 9*10^-21 cm³/s.The (CH3S)2O is further oxidized by NO2 in a sequence of reactions to give first (CH3SO)2 and subsequently (CH3SO2)2.The CH3S(O)NO is thermally unstable and decomposes to give CH3SO radicals and NO.The CH3SO species appears to react via CH3SO + CH3SNO -> (CH3S)2 + NO2 (9), 2CH3SO -> (CH3SO)2 (10) or possibly by CH3SO + CH3SNO -> (CH3S)2O + NO (11).