16919-98-5Relevant articles and documents
Reduction potentials determination of some biochemically important free radicals. Pulse radiolysis and electrochemical methods
Faraggi, M.,Klapper, M.H.
, p. 711 - 744 (2007/10/02)
In this review reduction potentials of unstable species is described.Both fast kinetics and electrochemical techniques are presented.Examples involving the determination of the reduction potentials of free radicals from amino-acids, peptides and nucleobases are discussed.
Kinetics and equilibria for reactions of the hexachloroiridate redox couple in nitrous acid
Ram,Stanbury, David M.
, p. 2954 - 2962 (2008/10/08)
The equilibria, kinetics, and mechanisms of the reactions of the IrCl62-/3- redox couple in nitrous acid have been investigated in aqueous solution at 25.0°C in nitric and perchloric acid media by conventional and stopped-flow spectrophotometry. In 1 M HClO4, when IrCl63- and HNO2 are mixed, the equilibrium HNO2 + H+ + IrCl63- ? NO + H2O + IrCl62- is established in a few milliseconds, with +d[IrCl62-]/dt = kf[H+][HNO2][IrCl63-] - kr[NO][IrCl62-], where kf = 1.8 × 104 M-2 s-1 and kr = 1.4 × 106 M-1 s-1. At high [HNO2], this reaction precedes a slow loss of IrCl62- that is due to formation of NO3-. In 1 M NO3- with [HNO2] > [IrCl63-] the rapid equilibrium is followed by zero-order formation of IrCl62-, and with [IrCl63-] > [HNO2] the process is autocatalytic. When IrCl62- is mixed with N(III) at pH ≥2, IrCl62- is consumed with rates that increase with acidity; at pH 62- is only partially consumed. All of these phenomena have been accurately simulated by numerical integration of the set of differential equations that arise from kf and kr as defined above and several previously established processes intrinsic to nitrous acid/nitric acid mixtures. The kf step is interpreted as rate-limiting diffusion-controlled electron transfer from IrCl63- to NO+. The reaction of NO2 with [Fe(TMP)3]2+ (TMP = 3,4,7,8-tetramethylphenanihroline), observed directly by pulse radiolysis, has a rate constant of 1.0 × 107 M-1 s-1; this rate constant, in conjunction with the results of a prior study of the reaction of NO2- with [Fe(TMP)3]3+, has confirmed the choice of thermodynamic data used to analyze the IrCl62-/3- reactions.