Chirality 2005-05-05

Configurational stability of 2-benzoylcyclohexanone: unexpected solvent effects on the rate of racemization.

Gilbert E Tumambac, Christopher J Francis, Christian Wolf

Index: Chirality 17(4) , 171-6, (2005)

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Abstract

The kinetics of the racemization of 2-benzoylcyclohexanone 1 in hexanes, ethanol, and mixtures thereof have been investigated by time dependence of enantiomeric purity using enantioselective HPLC. In pure hexanes and ethanol, the racemization half-lives were determined as 552 and 23.8 min, respectively, at 66 degrees C. Surprisingly, racemization of 1 in mixtures of hexanes and ethanol was found to involve an induction period followed by a sigmoidal decrease of the enantiomeric excess with half-lives varying between 11.5 and 24.0 min. This unexpected solvent influence on the rate of racemization of 1 was attributed to complex isomerization mechanisms involving three possibly interconverting enol tautomers of 1.(c) 2005 Wiley-Liss, Inc.