Kinetics of Methylcyclohexane Dehydrogenation over Pt-Al203 1559 indicate that hyperconjugation involving " bond" structures such as does not play an important role in stabilization of this ion. ExperimentalReagents.-Triphenylcarbinol, m.p. 162-163°, was prepared by recrystallization of Eastman White Label material. no Diphenylethylene (rm 1.6093) was prepared by distillation of Aldrich Chemical Co. DPE. Deuteriosulfuric acid was prepared by deuteriolysis of anhydrous sulfur trioxide using D20 (99.5%) from Stewart Oxygen Co.Measurements.-N.m.r. measurements were made with a Varían Associates model V-4300A spectrometer and 12 inch electromagnet. Chemical shifts were measured by the audio sideband technique with the use of a frequency counter.The chemical shifts of Tables I, II and VI were measured by use of trimethylsilane in a capillary placed in the tube which contained the material under study.

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.

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NotesYol. 65 in methanol and precipitation by excess ether. It was then heated in vacuo to constant weight.Absorption spectra were measured on a Cary recording spectrophotometer. The time dependence of the spectra was checked. Over a period of several days at room temperature the peak positions remained constant but slight changes in absorbance occurred. KINETICS OF THE CATALYTIC DEHYDROCYCLIZATIOX OF -HEPTANE