Mechanistic Studies on Oxide Catalysts. I. Reactions of Propene and Cyclopentene on Calcium Oxide

Mass spectrometry, gas chromatography and deuterium NMR spectroscopy have been used to examine the products from the reactions of propene or cyclopentene with deuterium on calcium oxide. The information so gained on the number, location and grouping of the deuterium atoms in the products provides evidence about the nature and reactivity of the adsorbed intermediates involved in the catalytic reactions. The dominant mechanism of exchange, which occurs readily on calcium oxide even at 240 K with either propene or cyclopentene, is interconversion between adsorbed alkene and adsorbed π-allyl species. Catalysis of addition reactions also occurs, but at rates which are about 102 to 104 times slower than exchange. Different mechanisms of exchange mainly involving vinylic intermediates are found on γ-alumina.