Thermodynamics of the Lipase-Catalyzed Transesterification of 1-Phenyl-1-Alkanols and Butyl Acetate in Organic Solvents

Published

January 16, 2003

Author(s)

Yadu D. Tewari, David J. Vanderah, J D. Rozzell

Abstract

The thermodynamics of the lipase-catalyzed transesterification reactions of butyl acetate and 1-phenyl-1-alkanols from C₁ to C₄ have been studied in organic solvents. Equilibrium measurements of the reactions with benzyl alcohol and (R)-(+)-1 phenyl ethanol were carried out in n-hexane, acetonitrile, 2-butanone, tert-butyl methyl ether, carbon tetrachloride and neat (no solvent added) at 298.15 K. The average value for the equilibrium constant and the standard molar Gibbs energy change δ_rG _m in these solvents for the reaction with benzyl alcohol (C₁) are 0.29 kJ mol and 3.1 kJ mol^-1, respectively; for the reaction with (R)-(+)-1-phenyl-1-ethanol (C₂) the respective values are 0.11 and 5.4 kJ mol^-1. The difference of 2.3 kJ mol^-1 in the values of δ_rG _m between the C₁ and C₂ alkanols is attributed to increased steric hindrance associated with the additional methyl group in (R)-(+)-1-phenylethanol. In addition, the temperature dependence of the equilibrium constants for the reactions with C₁ and C₂ alkanols were also studied in n-hexane. The standard molar Gibbs energy δ_rG _m, and entropy δ_rS _m changes at 298.15 K have been calculated from these results. The equilibrium constants for the reactions involving (R)-(+)-1-phenyl-1-propanol (C₃) and (R)-(+)-1-phenyl-1-butanol (C₄) were measured in n-hexane only and the values are both 0.11. The fact that the values of the equilibrium constants for the reactions involving C₂ to C₄ are constant is consistent with the view that no additional steric hindrance is caused by adding more than one methylene group to the 1-phenyl-1-alkanol reactant.

Citation

Journal of Molecular Catalysis B-Enzymatic

Volume

21

Issue

3

Pub Type

Journals

Keywords

(R)-(R)-(+)-1-phenyl-1-propanol, (R)-(R)-(+)-1-phenyl-1-propanol, (R)-1-phenylethanol, 1-butanol, benzyl alcohol, butyl acetate, enthalpy, equilibrium constant, lipase

Citation

Tewari, Y. , Vanderah, D. and Rozzell, J. (2003), Thermodynamics of the Lipase-Catalyzed Transesterification of 1-Phenyl-1-Alkanols and Butyl Acetate in Organic Solvents, Journal of Molecular Catalysis B-Enzymatic (Accessed December 13, 2024)