Kinetics of oxidation of heterocyclic secondary alcohols by N ‐chloro‐ r ‐2, c ‐6‐diphenyl‐ t ‐3 methyl piperidin‐4‐one (NCP) in perchloric acid medium

An investigation of the kinetics of oxidation of epimeric piperidin‐4‐ols, oxan‐4‐ols, and cyclohexanol by N ‐chloro‐ r ‐2, c ‐6‐diphenyl‐ t ‐3‐methylpiperidin‐4‐one (NCP) in aqueous acetic acid in the presence of perchloric acid shows that the reaction is first‐order each in substrate and oxidant. Both H 3 O + and Cl − which catalyze the reaction, exhibit a fractional order kinetics. While increase in ionic strength increases the rate slightly, an inverse dependence is observed between rate and solvent polarity. Addition of r ‐2‐ c ‐6‐diphenyl‐ t ‐3‐methylpiperidin‐4‐one, one of the reaction products, did not influence the rate. Also, no kinetic isotope effect has been observed. A plausible mechanism consistent with these observations is proposed and the relative reactivities of the substrates are explained on conformational grounds. © 1994 John Wiley & Sons, Inc.