Reactivity of Phthalimide-N-oxyl: A Kinetic Study

Abstract

The reactivity of phthalimide-N-oxyl radical (2), which is produced by an electrochemical one-electron oxidation of N-hydroxyphthalimide (1), was investigated. The self-decomposition of 2 obeyed second-order kinetics with respect to itself and the rate was little affected by changing the temperature or the concentration of dissolved oxygen, water or added base. In the reaction between 2 and benzhydrol or its a-deuterated derivative, the decay of the radical was first-order with respect to each component. The observed large deuterium isotope effect (kH/kD = 10.6 at 25 °C) is attributed to the rate-limiting hydrogen abstraction. Rate measurements were performed on the reaction with 24 other substrates which have one or more hydrogen atoms on a benzylic or allylic position or on a carbon adjacent to a hetero atom. © 1987, The Pharmaceutical Society of Japan. All rights reserved.