The reactions of ethane, propane, n-butane, isobutane and neopentane have been examined in the presence of deuterium on platinum films. Details of the products of exchange, hydrogenolysis and, where possible, isomerization are reported. The kinetic behaviour of the hydrogenolysis reaction showed a trend in that reactions of ethane were acceleratory, those of propane maintained a constant rate and those of molecules with four or more carbon atoms decelerated with time. The retardation in rates was much more marked with branched chain than with linear hydrocarbons.The results are discussed in terms of the nature of the adsorbed species accumulating on the surface, species possessing some carbonium ion character being likely precursors to the material responsible for the observed poisoning. Little additional mechanistic information was obtained from an analysis of the deuterium contents of the various molecules as exchange was fast compared to hydrogenolysis or isomerization, leading to rapid isotopic equilibration.A fragmentation correction scheme taking into account the influence of molecular coniposi tion on bond rupture has also been developed for analysis of the mass spectral data.

The reactions of n-butane, propane, ethane, and methane have been studied in the presence of deuterium on evaporated films of iron at temperatures such that exchange and, except in the case of methane, hydrogenolysis could be observed. Results indicated that the hydrocarbons interacted strongly with the catalyst surface such that exchanged products tended to be perdeuterioalkanes and the predominant product of hydrogenolysis was perdeuteriomethane. These observations suggest that the desorption of single carbon entities as methane may be the rate-determining step in n-butane and propane hydrogenolysis.

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The application of a combined gas chromatograph-mass spectrometer to catalytic reactions is described, particularly with reference to the reactions between deuterium and hydrocarbons over metal films. The analysis was complicated by partial separation of hydrocarbon isotopes in the gas chromatograph and different sensitivities of the equipment to 'light’ and ‘heavy’ methane. For the reaction of neopentane with deuterium over iron films exchange occurs 2.0 times more rapidly than hydrogenolysis and yields (CH 3 ) 3 (CH 2 D)C and (CH 3 ) 3 (CD 3 )C as the only initial deuterated neopentanes. Stepwise exchange occurs at 1.5 times the rate of multiple exchange. The absence of exchange products originating from an αγ -adsorbed intermediate suggests that αγ species are irreversibly adsorbed and lead directly to carbon-carbon bond rupture. The hydrogenolysis gives extensive degradation of neopentane, leading to 99% methane and small quantities of isobutane. The hydrogenolysis products were completely exchanged.

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