Steric effects on the oxidation of some substituted 4-oxanones by pyridinium fluorochromate

摘要

Kinetics of the oxidation of a few substituted 4-oxanones by pyridinium fluorochromate (PFC) in acetic acid-water (50% v/v) have been studied in the presence of sulphuric acid at 30° to 50℃. At the given acid range the reaction is found to be of second order, first order each with respect to oxi-dant and substrate. The effect of solvent polarity on reaction rates has also been studied. Activation energies and related thermodynamic parameters have been determined and compared. Under comparable set of conditions, enolisation proceeds faster than oxidation. A suitable mechanism and hence a corresponding rate equation has been proposed. The reactivities of oxanones have been rationalized on the basis of their conformational features.