The hydrogenation of olefines - I. The hydrogenation of ethylene and propene

Abstract

The mercury-photosensitized hydrogenation of ethylene has been studied at various olefine pressures and also in the presence of a separate third body. The disproportionation to combination ratio of the ethyl radicals which are the primary products of the reaction has been determined and found, under suitable conditions, to be in good agreement with the values obtained with ethyl radicals originating from a number of other sources. The hydrogenation of propene has been studied, the products separated by vapour-phase chromatography, and analyzed individually in the mass spectrometer. The disproportionation to combination ratio for iso propyl radicals has been found to vary with pressure in a similar way to that for ethyl radicals and similar hot radical and deactivation mechanisms are postulated in either case. A value of the ratio corrected for abstraction has been obtained in a way comparable with that used for ethyl radicals. The value agrees with that obtained for iso propyl radicals from other sources. It has been demonstrated that iso propyl radicals are able in certain circumstances to abstract from propene molecules yielding allyl radicals. C 3 H 7 + C 3 H 6 → C 3 H 8 + C 3 H 5 , as well as the more generally accepted abstraction by hydrogen atoms (Darwent & Roberts 1953).