Methylcyclopropane hydrogenolysis

Normand et al. have studied Pd deposited on several metal oxide supports in reactions of methylcyclopropane hydrogenolysis, 3-methylhexane aromatization, and in Fischer-Tropsch catalysis 23 Three classes of oxides were studied, those that were not reducible such as Re2C>3, those with anion vacancies produced during reduction like Ce02, and those with intrinsic anion vacancies such as nonstoichiometric Pt60h and Tb407. Hydrogenolysis reactions were found to occur on Pd sites whereas aromatization reactions were believed to be... 

Methylcyclopropane hydrogenolysis has also been studied over Pd/ Si02 and the TOF passes through a flat maximum at about FE = 0.65 (278). Over Rh/Si02, this reaction is found to show a marked sympathetic structure sensitivity (279). 

The present paper reviews the physical and chemical evidence for the above rules obtained over the last several years from ultrahigh vacuum surface science studies of molybdenum single crystals chemically modified by 0, C, S, and B. Additionally, the results of recent studies of methylcyclopropane hydrogenolysis will be presented which illustrate the influence of surface acid/base sites on catalytic hydrocarbon conversions. The surface coverage of each modifier was determined by quantitative Auger electron spectroscopy or x-ray photoelectron spectroscopy (XPS). The atomic structure of oxygen, carbon, and sulfur adlayers below one monolayer (ML)... 

Burwell and coworkers (ref. 15) studied the transformation of methylcyclo-propane on the same series of Pt catalysts, and found it to be mildly structure-sensitive. The TOF in the hydrogenolysis of methylcyclopropane increased continuously as a function of the dispersion. The total TOF varied by a factor of two, while the activation energy of the reaction was independent of the percentage of metal exposed.These facts offered a simple geometric expla-... 

The hydrogenolysis of methylcyclopropane is quite structure sensitive on Rh/Si02 (194), whereas over Pd/Si02 the variations in turnover frequencies with Pd particle size are not very pronounced (182). 

Thermolysis of enantiopure sulfonyl pyrazolines 241 afforded sulfonyl cyclopropanes 242 in a completely stereoselective manner (Scheme 17) <2004OL4945>. Both cyclopropanes 243 and alkylidenecyclopropanes 244, containing one or two chiral carbon atoms, one of them being quaternary, were obtained by hydrogenolysis of the G-S bond and under Julia conditions, respectively. Thermal dediazotization of 3-(l-fluorovinyl)-3-methylpyrazoline 245 at 250°G afforded l-(l-fluorovinyl)-l-methylcyclopropane 246, which was capable of isomerizing further, at 600°G, to... 

The physical and chemical properties of the oxygen modified molybdenum surfaces described aboye indicate the formation of acidic sites with yariable strength and hard/soft character as a function of oxygen coyerage. The hydrogenolysis of methylcyclopropane (MCP) was inyestigated to probe the catalytic properties of these surfaces. A full account of this study will appear elsewhere (Touyell, M. S. Stair, P. C. J. Catal. submitted). 

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