Heterogenous Catalysis in Organic Chemistry. 3. Competitive Adsorption of Solvents during Alkene Hydrogenations

Article abstract of DOI:10.1021/jo00199a021

A single turnover reaction sequence has been used to determine the extent to which solvent can compete for adsorption sites in the hydrogenation of alkenes over Pt and Pd catalysts.Both methanol and ethanol are adsorbed readily on both Pt and Pd catalysts converting the ³M alkene saturation sites into ²M isomerization sites and original ²M sites into unreactive ¹M sites. tert-Butyl alcohol interacts only slightly with Pt catalysts presumably because of steric factors, but such restraints are not exhibited with Pd species.Over Pd the tert-butyl alcohol has adsorption characeristics similar to ethanol. 2-Propanol, on the other hand, enters into the reaction as an hydrogen donor in a transfer hydrogenation.THF and acetic acid are also adsorbed on the metal surface, but with THF there is little if any increase in isomerization, only a decrease in saturation capability.Acetic acid lies somewhere between THF and methanol.Other solvents such as ethal acetate, ether, and acetone have little, if any, effect on catalyst activity.