MECHANISM STUDY OF SUGAR AND SUGAR ALCOHOL HYDROGENOLYSIS USING 1,3-DIOL MODEL COMPOUNDS

Knowledge of the bond cleavage mechanism governing sugar and sugar alc ohol hydrogenolysis is important-to control of the selectivity of suga r and sugar alcohol hydrogenolysis. Previous work by others has result ed in the suggestion of a variety of mechanisms to explain the C-C cle avage in sugar and sugar alcohol hydrogenolysis, and has not provided any definitive evidence to elucidate either the C-C or C-O cleavage me chanism. In this work, we present a mechanism study carried out using 1,3-diol model compounds. Our experimental results indicate that cleav age of the C-C and C-O bonds in hydrogenolysis is through retro-aldoli zation and dehydration of a beta-hydroxyl carbonyl, respectively. The structure of this beta-hydroxyl carbonyl is already contained in an op en-chain sugar molecule, and is generated from the sugar alcohol molec ule by dehydrogenation. The intermediates from both C-C and C-O cleava ge are subsequently hydrogenated to yield alcohols or polyols. This me chanism of sugar and sugar alcohol hydrogenolysis provides us a good b ackground to understand factors that control the selectivity in sugar and sugar alcohol hydrogenolysis. Based on this understanding, a ratio nal approach to control of the selectivity of sugar and sugar alcohol hydrogenolysis may be developed.