The hydrogen abstraction reaction of benzophenones in micellar interiors was studied by the effect of a short, resonant microwave pulse on the recombination kinetics under magnetic fields of approximately 0.3 T. This technique allows all the significant rate constants in the reaction to be determined, in particular the singlet state recombination rate constant, which is very difficult to accurately determine by other techniques. This is determined to be 1.90 × 107 s-1 for benzophenone (BP) and 1.83 × 107 s-1 for decafluorobenzophenone in sodium dodecyl sulfate (SDS) micelles, indicating that this value is not limited by the rate of spin mixing, and thus that the kinetic approach used is justified. It also indicates that recombination is limited by re-encounter frequency and is not dependent upon substitution in the ketyl radical. All kinetic parameters are extracted for each system using a combination of single pulse and pulse shift measurements. Data are also presented for the reactions of BP in SDS solutions of high salt concentration, in polyoxyethylene dodecyl ether (Brij 35), and in hexadecyltrimethylammonium chloride micelles. The rate constants reveal useful information on the effects of the both the micelle interior and the nature of ketyl radical on the recombination kinetics
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