Kinetics of Nitroxyl Radical Reactions a Pulse-radiolysis Conductivity Study

Summary

Absolute rate-constants for the reaction of the nitroxyl free radicals TAN and TMPN with radiation-chemically-formed radicals and ions have been determined. k(TAN+X) (in M⁻¹ sec⁻¹) = 4·0 × 10⁹ (for X=OH·), 2·9 × 10¹⁰ (e_aq⁻), 8·0 × 10⁹ (H·), 7·2 × 10⁸ (·CH₂OH), 4·0 × 10⁸ (CH₃ĊHOH), 4·3 × 10⁸ ((CH₃)₂ĊOH) 2·8 × 10⁸ (·CH₂(CH₃)₂ COH), 5·9 × 10⁷ (glucose radical), 4·0 × 10⁸ (c-C₅H₉·), and k(TMPN + X) = 3·4 × 10⁹ (OH·), 7·8 × 10⁹ (e_aq⁻), 4·9 × 10⁹ (H·), 4·4 × 10⁸ (·CH₂OH), 4·9 × 10⁸ (CH₃ĊHOH), 3·6 × 10⁸ ((CH₃)₂ĊOH), 1·5 × 10⁸ (·CH₂(CH₃)₂COH), 4·9 × 10⁷ (glucose radical), 4·3 × 10⁸ (c-C₅H₉·). Direct measurements by means of a pulse-radiolysis conductivity technique were based on the formation and destruction of charged species in these reactions within certain pH ranges. It is indicated that the radiosensitizing nitroxyls undergo both redox and addition reactions.