A Thermodynamic Study of Ketoreductase-Catalyzed Reactions. 2. Reduction of Cycloalkanones in Non-Aqueous Solvents

Published

April 1, 2006

Author(s)

Yadu D. Tewari, Karen W. Phinney, J F. Liebman

Abstract

The equilibrium constants for the ketoreductase-catalyzed reactions (cycloalkanone + 2-propanol = cycloalkanol + acetone) have been measured inn-hexane, n-pentane, and supercritical carbon dioxide (pressure P = 8.0 to 12.0 MPa). The cycloalkanones included in this study were: cyclobutanone, cyclopentanone, cyclohexanone, cycloheptanone, and cyclooctanone. The equilibrium constants for the reactions involving cyclobutanone and cyclohexanone were measured in n-hexane over the range T = 288.35 K to T = 308.05 K. The thermodynamic quantities at T = 298.15 K are:K = 0.763 0.001; ?rG?m = (0.670 0.002) kJ mol-1; ?rH?m = (1.09 0.11) kJ mol 1, and ?rS?m= -(5.9 0.4) J K-1 mol-1 for the reaction involving cyclobutanone; and K = 15.7 0.2; ?rG?m = (6.82 0.02) kJ mol-1; ?rH?m = (4.6 1.0) kJ mol-1, and ?rS?m= (7.4 3.3) J K-1 mol-1 for the reaction involving cyclohexanone, respectively. An inspection of the equilibrium constants for these reactions in n hexane, n pentane, and SCCO2 shows that solvent dependence is not significant. The equilibrium constants of cycloalkanones decrease with increasing value of the number of carbons, NC with the exception of cyclohexanone. The cyclohexanol, which adopts a tetrahedral conformation around each carbon, is thermodynamically favored and more stable compared to other cycloalkanol rings, and this is reflected in the significantly higher value of theequilibrium constant obtained for this reaction. Comparisons with results obtained by using two independent thermochemical routes are also made.

Citation

Journal of Chemical Thermodynamics

Volume

38

Issue

No. 4

Pub Type

Journals

Keywords

2-propanol, acetone, cycloalkanol, cycloalkanone, equilibrium constant, ketoreductase, n-hexane, n-pentane, supercritical carbon dioxide

Citation

Tewari, Y. , Phinney, K. and Liebman, J. (2006), A Thermodynamic Study of Ketoreductase-Catalyzed Reactions. 2. Reduction of Cycloalkanones in Non-Aqueous Solvents, Journal of Chemical Thermodynamics (Accessed October 10, 2024)