Hydrogenolysis of cyclopropanes

Hall et al. (63) found that the active species in the hydrogenolysis of cyclopropane are Mo(IV) in reduced M0O3-AI2O3 catalysts. Also, Burwell and Bowman found that the hydrogenolysis of cyclopropane at 100 C (64) and also propane at 300°C (65) occurs over Mo(IV), Mo(II), and Mo(0) catalysts, which were prepared from Mo(CO)g on AI2O3. The average valence state... 

Similar conclusions have been drawn from a study of the hydrogenolysis and isomerization of cyclopropane over catalysts made up of supported rhenium clusters of differing nuclearity.29 The hydrogenolysis of cyclopropane was found to take place only over those catalysts having at least a Re3 nuclearity while the hydrogenation of propene, an isomerization product of cyclopropane, took place on Re I species (Eqn. 3.1). 

The rate of hydrogenolysis of ethane to methane over Ru(0001) is much more slowly poisoned by sulfur than is methanation (50). The hydrogenolysis of cyclopropane to methane, ethane, and propane has been studied by Goodman over sulfur-dosed Ni(lll) and Ni(100) (73). The production of methane and ethane on Ni(l 11) and methane on Ni(100) is dramatically poisoned by low sulfur coverages. The yield of propane plus propylene decreases much more slowly. In contrast to the clean Ni(lll) surface, ethylene production increases, becoming a significant product, after sulfur addition. Overall, the addition of sulfur causes a reduction in the ability of the Ni surface to cleave C—C bonds. 

D.R. Kahn, E.E. Petersen, and G.A. Somoijai. The Hydrogenolysis of Cyclopropane on a Platinum Stepped Single Crystal at Atmospheric Pressure. J. Catal. 34 294... 

Tn recent years ultrahigh vacuum methods have been applied to cata-lytic studies on initially clean metal surfaces having low surface area. In several instances (the hydrogenolysis of cyclopropane over platinum (I) and the catalytic methanation reaction over rhodium (2) and nickel (3)) a link between ultrahigh vacuum methods and conventional catalytic measurements was established. That is, specific reaction rates over low area cm ) catalyst samples agreed with specific reaction... 

We have already noted that the occurrence of hydrogenolysis of cyclopropane is easier than that of propane, because the initial chemisorption needs a smaller energy input. The fact that methane and ethane are the usual products shows that a second C—C bond breaking is followed by the speedy desorption of the C2 fragment, and the somewhat special and exigent conditions needed for total conversion to methane reflects the known greater stability of the C—C bond in ethane (or its predecessor). There have been several detailed discussions of likely intermediate strucutres those shown in Scheme 11.1 are as reasonable as any. 

Cyclopropane and Cyclopropene Adds.— The undesirable physiological properties of cyclopropene acids such as malvalic acid (20 R = H) and sterculic acid (21 R = H) and their presence, albeit in small amount, in cottonseed oil has aroused interest in these compounds. The content of cyclopropene acids is reduced by heating with palladium catalysts, though not with nickel or platinum catalysts. Palladium treatment cleaves the cyclopropene ring and produces methyl- and methylene-substituted acids. Hydrogenolysis of cyclopropane acids is reported to give methyl-substituted fatty acids which can be identified by their g.l.c. behaviour on capillary columns. The chemical reactions of cyclopropene acids (malvalic and sterculic) shown in Scheme 5 have been reported. ... 

Hydrogenolysis of cyclopropane was first reported in 1907 [2]. Currently, its ring opening is successfully exploited in the synthesis of tetraisopropylmethane [3] and several natural products (Scheme 2.1) [4]. 

Fig. 3. Dependence of initial rate, R/Torr min on initial hydrogen pressure Pu/Torr, In the hydrogenolysis of cyclopropane to propane catalysed at 313 K byWsIlIca (a) and by EUROPT-1 (b). P° - 125 Torr. [1 Torr = 133.3 Pa]. In (a) the full curve represents a variation of rate given by eqn. 1 (see text), and the dotted and dashed curves show the corresponding theoretical variations of surface coverages. In (b) the full curve describes the experimental variation of rate, and the dotted and dashed curves represent predicted behaviour according to eqn.l (see text).

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