Kinetic study of hydrogen transfer from benzyl alcohol to aliphatic aldehydes catalysed by heterogenised ruthenium(II) catalysts

Abstract

Aliphatic aldehydes were reduced to corresponding alcohols by transfer hydrogenation in the presence of Ru(II) complexes bound to swellable polymer matrices. Benzyl alcohol was used as hydrogen donor because of its strong hydrogen donor ability. The kinetics of the reaction has been measured between 100 and 140 • C. The results showed that reaction rate depended on the structure of aldehydes and concentrations of aldehyde. Also reaction rate depended on the concentration of hydrogen donor, and on the amount of catalyst. The reaction proceeded efficiently in halogenated hydrocarbon solvents. The metal leaching was different for different catalytic runs and it was most pronounced in the first catalytic run. The observed activation energy, E a = 18 ± 1 kcal/mol was obtained, suggested that process in predominantly chemically controlled reaction. A general reaction mechanism and rate equation have been proposed.