Reactions of cyclopropane and deuterium over supported metal catalysts

Abstract

The reaction of cyclopropane and deuterium has been studied at low temperatures over a number of supported metal catalysts. The main reaction was normally ring-opening, yielding a mixture of isotopic propanes which were analysed mass-spectrometrically and by deuterium NMR spectroscopy. The patterns of isotopic propanes varied substantially with the nature of the metal and provided information about the types of adsorbed intermediates involved in the mechanisms of the reactions.

The reaction of propene and deuterium was also followed over supported platinum catalysts. In contrast to the results with cyclopropane, exchange of propene occurred and the propanes formed from propene were markedly different from those from cyclopropane, reflecting differences in the mechanisms of the reactions.

Evidence of dual-function catalysis was obtained using alumina-supported iridium with cyclopropane and deuterium; exchange took place on the support and ring-opening on the metal. Similar dual functionality was observed for reactions of methylcyclopropane or 1,1-dimethylcyclopropane with deuterium over the same Ir/Al₂O₃ catalyst. As a consequence of the present work, the high selectivity for the exchange of primary hydrogen atoms in various hydrocarbons over Ir/Al₂O₃ is now considered to be a function of the support rather than of the metal.