OH], and different organic solvents ( ) in order to clarify the second order rate constants for (R)-(1) and (S)-(1), and the enantioselectivity which are affected by solvent 309Correspondence to: Hirofumi Hirata, Department of Bioscience and Technology, School of Engineering, Hokkaido Tokai University, 5-1 Minamisawa, Minami-ku, Sapporo 005-8601, JAPAN E-mail: hirata@db.htokai.ac.jp Accepted February 26, 2007 (received for review December 7, 2006 Journal of Oleo Science Copyright ©2007 by Japan Oil Chemists ' Society J. Oleo Sci. 56,(6) 309-317 (2007) Abstract: Lipase-catalyzed acetylation of 2-alkanol with vinyl acetate has been studied kinetically using Burkholderia cepacia lipase (BCL), enantiomerically pure (R)-and (S)-2-alkanols and different organic solvents. The rate equation was derived by the steady state method for the simplified mechanism. The second order rate constants (k R and k S ) for (R)-and (S)-2-alkanols were evaluated from the slopes of the double reciprocal plots, v -1 vs. [2-alkanol] -1 , where v is the initial rate of the reaction. The log k R value increased with the solvent hydrophobicity log P, where P is a partition coefficient of a given solvent between octanol and water. The log k S value also increased with log P except the bulky solvents such as 1,4-dioxane and cyclohexane, in which the rates were faster than those expected from the log k S vs. log P plot. The slope of log k S vs. log P plot was larger than that for (R)-2-alkanol. Thus, log E (E=k R /k S : enantioselectivity) decreased with log P except the bulky solvents. The rate constants and the enantioselectivity were different depending on the structure (carbon number CN) of 2-alkanol. The log E vs. CN plot was minimized at CN=8 and 10 and the log k S vs. CN plot maximized at CN=8 and 10. In contrast the log k R vs. CN plot showed a different feature from the log E vs. CN plot. These facts suggest that dependence of E on CN is more strongly affected by the reactivity of (S)-2-alkanol than that of (R) isomer in this acetylation. Kinetic Studies on Lipase-Catalyzed Acetylation of 2-Alkanol with Vinyl Acetate in Organic Solvent