The deuteration of some cyclic olefins on iron and other transition metal films

Abstract

The products formed by the deuteration of cyclo hexene on films of nickel, palladium, platinum and tungsten at — 35 and 0 °C were determined by means of a mass spectrometer. Studies over a greater range of temperatures were made with cyclo pentene, cyclo hexene, cyclo heptene, nor bornylene, 4-methylmethylene cyclo hexane and 4-methyl cyclo hexene on iron films. At low temperatures the deuteration of the unsubstituted olefins yielded products mainly in the range d 0 - cyclo -alkane to d n -cyclo -alkane ( n representing the number of carbon atoms in the molecule). Evidence was obtained that these patterns of products were caused by the interconversion, on the surface, of adsorbed cyclo -alkene molecules and cyclo -alkyl radicals. The shape of these adsorbed species restricted the formation of more highly deuterated alkanes although some of these were formed by the deuteration of deutero-olefins produced during the course of the reactions. A second type of reaction, producing cyclo -alkanes in the range d n +1 to d 2 n and extensive exchange of the deuterium, occurred with iron films at higher temperatures. The additional activation energy required for this reaction was about 4 to 5 kcal/mole with the C 5 , C 6 and C 7 olefins and the possible adsorbed intermediates, involved in the reaction, are discussed. Sintering of the iron films markedly reduced the amount of this second type of reaction. Various interesting features in the patterns of products from the deuteration of the other olefins on iron are reported and discussed. A preliminary investigation was made on the deuteration of 1,4- cyclo hexadiene and cyclo pentadiene on iron films and yielded results which were entirely consistent with the proposed mechanism for the deuteration of the olefins.