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Catalysis over Supported Metals 95 rather poor fit of the calculated and experimental chemical shift-concentration curves for the (CH3)20~BC13 and (CH3)2-0-BF3 systems could also be explained on this basis. An additional experimental difficulty arising from the high volatility of (CH3)20-BF3 in dichloro-methane would also affect the accuracy of the ¿-concentration plot.Acknowledgments. The financial assistance of the National Research Council and the National Cancer Institute of Canada are gratefully acknowledged.

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The kinetics of n-pentane isomerization over a Pt-A!203 catalyst were investigated at 372°. The reaction was carried out in a flow reactor in the presence of added hydrogen at pressures ranging from 7.7 to 27.7 atm. and hydrogen to n-pentane ratios ranging from 1.4 to 18. The rate of isomerization was found to correlate with the n-pentane to hydrogen mole ratio and to be independent of total reactor pressure at a fixed n-pentane to hydrogen ratio. These results can be explained in terms of the postulated mechanism by which isomerization proceeds via an olefin intermediate present in equilibrium concentration. According to this mechanism n-pentane dehydrogenates on platinum sites to n-pentene, which in turn migrates to acidic sites to isomerize, presumably by a carbonium ion mechanism. The rate-controlling step is the isomerization of the intermediate olefin on acidic sites.