The hydrogenative ring-opening reactions of five alkyl-substituted cyclopropanes [ethyl-(ECP), cis-1,2-dimethyl- (cDMCP) and trans-1,2-dimethyl- (tDMCP), 1,1-dimethyl-(1,1DMCP) and 1,1,2,2,-tetramethyl- (TMCP) cyclopropane] over Pt/SiO2 catalyst were studied. The shapes of the curves depicting product formation rate vs. H2 pressure suggest that CC as well as CH bond rupture occurs upon adsorption. Based on stereochemical considerations and on comparisons of product formation at the maximum rates, it is proposed that cDMCP forms a flat-lying complex over the surface of the catalyst and tDMCP, 1,1DMCP and TMCP react through edge-on surface intermediates. IR measurements concerning the reaction of ECP support the proposed dissociative adsorption.
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