Abstract.A study has been made of the catalytic inhibition of the autoxidation of hydrocarbons at 130°C by secondary amines and derivatives thereof (hydroxylamines and nitroxides). Owing to a better resistance towards side-reactions that cause decomposition of the inhibitor, certain dialkylamines are much more efficient than diarylamines. Some of the dialkylamines examined are capable of scavenging several hundreds of propagating radicals per molecule of inhibitor in autoxidizing alkanes and a few thousand radicals in autoxidizing n-hexylbenzene.

Abstract.A study has been made of the mechanism of the catalytic inhibition of autoxidation of hydrocarbons at 130°C by secondary amines and derivatives thereof (hydroxylamines and nitroxides). From the effect of hydrocarbon structure on the inhibition and from the various reactions of possible intermediates of the catalytic cycle, it is concluded that alkyl and alkylperoxyl radicals are scavenged alternately. Reaction of an alkyl radical with a nitroxide produces an 0-alkylated hydroxylamine. In the case of tertiary alkyl radicals this hydroxylamine decomposes thermally ~ via transfer of the P-hydrogen from the alkyl group to the nitroxide moiety ~ into olefin and hydroxylamine. The hydroxylamine is subsequently oxidized back to the nitroxide by alkylperoxyl radicals. Kinetic data on the individual steps of the cycle are in accord with the observed inhibiting effect.

Abstract. Reductive cleavage of the sp3 carbon-sulfur bond in alkyl-or aryl-substituted 2-mercaptoor 2-amino-6H-l,3-thiazines with sodium in liquid ammonia affords almost quantitative yields of the sodium salts of 1 -alkenyl-dithiocarbamates and -thiourea, respectively. The dithiocarbamates can be converted into I-alkenyl isothiocyanates by reaction with chloroformates and subsequent pyrolysis to give overall yields of 54-88S:;. Cis-trans isomerization of the 1 -alkenyl isothiocyanates can only be achieved by irradiation.

Abstract. The course of the reductive ring-opening reactions of 2-mercapto-, 2-hydroxy, 2-amino-, '-methylamino-and 2-dimethylamino-4-methylthiazoles with sodium in liquid ammonia, yielding substituted propenethiolates. has been found to depend on the nature of the hetero substituent. The mechanism of the ring opening is discussed.

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