Reactions of cyclopentene and deuterium over supported-metal catalysts

Abstract

The reaction of cyclopentene and deuterium has been studied over a range of silica-supported catalysts with the products of both the exchange and addition reactions analysed by combined mass spectrometry, gas chromatography and deuterium NMR spectroscopy. The NMR data for the exchanged cyclopentenes reveals the distribution of the deuterium label across the molecules and, taken in conjunction with the mass spectrometric product distributions, indicate an exchange mechanism involving initial olefinic or allylic exchange. Subsequent propagation of the exchange occurs through interconversion between the adsorbed alkene and surface allyl and/or alkyl hydrocarbon fragments. All the catalysts gave a wide distribution of deuteriocylopentanes. Again, alkene/alkyl interconversion is important in the production of the deuterioalkanes, however dilution of the deuterium label from the concurrent alkene exchange has a considerable influence on the final alkane product distribution.