Kinetics of Nitroxyl Radical Reactions a Pulse-radiolysis Conductivity Study

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Abstract
Absolute rate-constants for the reaction of nitroxyl free radicals TAN [2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl] and TMPN with radiation-chemically-formed radicals and ions were determined. k(TAN + X) (in M-1 s-1) = 4.0 .times. 109 for X = OH.cntdot.), 2.9 .times. 1010 (eaq-), 8.0 .times. 109 (H.cntdot.), 7.2 .times. 108 (.cntdot.CH2OH), 4.0 .times. 108 (CH3.ovrhdot.CHOH), 4.3 .times. 108 ((CH3)2.ovrhdot.COH) 2.8 .times. 108 (.cntdot.CH2(CH3)2 COH), 5.9 .times. 107 (glucose radical), 4.0 .times. 108 (c-C5H9.cntdot.), and k(TMPN + X) = 3.4 .times. 109 (OH.cntdot.), 7.8 .times. 109 (eaq-), 4.9 .times. 109 (H.cntdot.), 4.4 .times. 108 (.cntdot.CH2OH), 4.9 .times. 108 (CH3.ovrhdot.CHOH), 3.6 .times. 108 ((CH3)2.ovrhdot.COH), 1.5 .times. 108 (.cntdot.CH2(CH3)2COH), 4.9 .times. 107 (glucose radical), 4.3 .times. 108 (c-C5H9.cntdot.). 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. The radiosensitizing nitroxyls may undergo both redox and addition reactions.
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