The ionic liquid, 1-butyl-3-methylimidazolium bis[(trifluoromethyl) sulfonyl]amide ([Bmim] [NTf2]), was used as a reaction medium for the kinetic resolution of rac-2-pentanol catalyzed by free Candida antarctica lipase B, using vinyl propionate at 2% (v/v) water content. The synthetic activity of lipase in [Bmim] [NTf2] was up 2.5-times greater than in hexane, and showed high enantioselectivity (ee > 99.99%). The optimal temperature and pH were 60degreesC and 7, respectively. A decrease in water activity (a(w)) produced a decay in synthetic activity, and an exponential increase in selectivity.