Enantioselective hydrogenation of ethyl pyruvate over
cinchonidine-Pt/Al2O3 catalyst. A reaction kinetic approach |
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Authors: | J L Margitfalvi E Tálas E Tfirst |
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Affiliation: | (1) Institute of Surface Chemistry and Catalysis, Chemical Research Center, Hungarian Academy of Sciences, 1525 Budapest, P.O. Box 17, Hungary |
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Abstract: | A new reaction kinetic approach was used to describe the enantioselective hydrogenation of ethyl pyruvate over cinchona-Pt
catalyst. The above reaction was considered as the sum of two parallel reactions: (i) racemic hydrogenation resulting in R-
and S-product in equal amount and (ii) enantioselective hydrogenation leading to the exclusive formation of one of the two
optically isomers. New terms such as accdiff and k
e/k
r (where k
e and k
r are the rate constants of the enantioselective and racemic hydrogenation, respectively) were introduced to characterize the
relationship between the enantioselective and the racemic hydrogenation reactions. Results obtained show that the formation
of R-product is rate accelerated, while the formation of S-product is decelerated. The results indicate also that the overall
rate increase is a kinetic phenomenon and cannot be attributed to the suppression of the poisoning effect of CO or oligomers
formed from ethyl pyruvate. The strong rate acceleration effect of achiral tertiary amines (ATAs) added to the reaction mixture
was attributed to the decrease of the loss of modifier during the hydrogenation experiments. |
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Keywords: | enantioselective hydrogenation ethyl pyruvate Pt/Al2O3 cinchonidine kinetic approach rate acceleration rate deceleration |
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