Selective Hydrogenation of Unsaturated Aldehydes with the CoCl2-Modified Raney Cobalt Catalyst

Abstract

(E)- and (Z)-3,7-dimethyl-2,6-octadien-l-ol ((E)- and (Z)-[l]) and 3,7-dimethyl-6-octen-1-ol were preferentially obtained respectively by hydrogenations of eitral [2], which is a mixture of (E)- and (Z)-3,7-dimethyl-2,6-octadienal, and of citronellal [3] in the presence of the CoCl2-modified Raney Co catalyst at 30-65°C under atmospheric pressure. When the hydrogenation of [2] was stopped at the consumption of 0.2-0.3 mol of hydrogen, more than 92% of the product was a mixture of (E)- and (Z)-[1]. The best selection (99%) was observed when 1-propanol was used as a solvent. The rates of hydrogenations of [2] and [3] were dependent on the sort of solvent. The effect of the solvent on the efficiency of hydrogenation rate was observed in the following order; methanol>ethanol>l-propanol> 2-propanol. © 1982, The Chemical Society of Japan. All rights reserved.