Pulse Radiolysis Studies of the Radiosensitizer Nor-pseudopelletierine-N-oxyl (NPPN)

Summary

The rate of the reactions between the stable free radical radiosensitizer Nor-pseudopelletierine-N-oxyl (NPPN), and the primary and some secondary radiation-induced radicals, have been measured in aqueous solution. Rapid reactions are observed in all cases with a typical rate constant of 5 × 10⁹ M⁻¹ sec⁻¹ for the reaction of NPPN with OH radicals. Triacetoneamine-N-oxyl was also found to react rapidly with OH, in disagreement with another published estimate. The yield of destruction of the nitroxyl group absorption at 242 nm has also been measured in several systems. Each of the primary radicals modify the nitroxyl chromophore but the OH radical was also found to attack other sites on the molecule, probably via hydrogen abstraction from the methylene groups. The possible use and advantages of NPPN as a general radical scavenger in free radical studies is discussed.