Hydrated electrons analysis

There have been several extensions of this analysis to incorporate the effect of time-dependent rate constants (hardly appropriate when there are so few reactants present) and an initial skewed Gaussian distribution for the hydrated electron which give an initial zero density at the origin... 

Debye—Smolucholowski rate coefficient does indicate that these reaction rates are in broad agreement (see Table 2). If it is accepted that some hydrodynamic repulsion occurs, less than implied by the Deutch and Felderhof analysis [70], but as suggested by Wolynes and Deutch [71], then the reaction radii are as listed in Table 2. However, if allowance is also made for the larger size of some reactants than the hydrated electron, then the agreement between experiment and theory becomes satisfactory. Nevertheless, the uncertainty of diffusion coefficients and the crystallographic or true reaction radii, R, let alone the rate of reaction of encounter pairs, makes a comparison of these relatively small effects difficult. 

Schmidt KH, Flan P, Bartels DM (1995) Radiolytic yields of the hydrated electron from transient conductivity improved calculation of the hydrated electron diffusion coefficient and analysis of some diffusion-limited (e )aq reaction rates. J Phys Chem 99 10530-10539 Schoneich C, Aced A, Asmus K-D (1991) Halogenated peroxyl radicals as two-electron-transfer agents. Oxidation of organic sulfides to sulfoxides. J Am Chem Soc 113 375-376 Schuchmann Fl-P, von Sonntag C (1981) Photolysis at 185 nm of dimethyl ether in aqueous solution Involvement of the hydroxymethyl radical. J Photochem 16 289-295 Schuchmann Fl-P, von Sonntag C (1984) Methylperoxyl radicals a study ofthey-radiolysis of methane in oxygenated aqueous solutions. Z Naturforsch 39b 217-221 Schuchmann Fl-P, von Sonntag C (1997) Heteroatom peroxyl radicals. In Alfassi ZB (ed) Peroxyl radicals. Wiley, Chichester, pp 439-455... 

The experimental methods used in the investigation of the hydrated electron include competition kinetics and product analysis, as well as pulse-radiolysis and flash-photolysis techniques. All these methods have... 

Goulet T, Jay-Gerin J-P. (1992) On the reactions of hydrated electrons with OH and HjO+. Analysis of photoionization experiments. J Chem Phys 96 5076-5087. 

Figure 7. Spectral contributions of transient electronic configurations triggered by the femtosecond UV excitation of aqueous chloride ions. The relative spectral contributions are obtained from the computed analysis of time-resolved UV-IR femtosecond spectroscopic data. A first photophysical channel, including a non-adiabatic transition from a p-like excited hydrated electron state (e hydV to an s-like ground hydrated electron state. B spectral contributions of two well-defined transient fe Cl pairs. The presence of counterions (Na ) influences the dual behavior of these transient electronic configurations. C Direct identification of the spectral band assigned to near-infrared fe Cl pairs, made by using a cooled Optical Multichannel Analyzer (OMA 4) equipped with CCD detectors (1024 X...

Specific electron scavengers suppress the transient absorption obtained in the pulse radiolysis of water. By measurement of the efficiency of this process, it is possible to determine the rate coefficient for the reaction of the hydrated electron with the scavenger. Solutes are restricted to those which do not absorb significantly in some region of the hydrated electron spectrum. Computer programs have been developed for kinetic analysis of the oscilloscope traces and it is thus possible to obtain rate coefficients... 

Many of the reactions of inorganic compounds with hydrated electrons are extremely rapid, their reactions being essentially diffusion controlled. A detailed analysis of these reactions reveals new information on the mode of interaction of hydrated electrons with reactive inorganic solutes. 

The preparation of solutions, irradiation of the samples, and analysis of decay curves by Chloe follow our previously described techniques (24). Hydrated electron scavengers were removed from the hydrogen-saturated matrix by its pre-irradiation before injection of the solute in cases where concentrations of the order of 10/xM solute were tested. The sources of supply of the chemicals used appear in Tables I and II. 

Kinetic analysis of the simultaneous decay of the hydrated electron at 650 n.m. gave rate constants which were within 10% of this value. 

In RNase the protonated histidyl residues and the cystyl residues are apparently the most reactive sites in reactions with the hydrated electron. This was concluded from measurements of the absolute reaction rates of amino acids, peptides, and proteins (I, 2) and from an analysis of the reactivity of proteins in terms of the reactivities of the individual amino acids. At a pH of about 9 the histidyl residues are dissociated and have a low reactivity. The absolute reaction rate constant of RNase at this pH is 5 X 109 M-1 sec.-1 (2) and can only be explained on the assumption that the four disulfide bridges inside the protein molecule contribute to its reactivity. This contribution, however, is less than would be expected for cystyl residues which show a rate constant of about Ke-aq = 2 X 1010 M 1 sec.-1. The lack of a full contribution from the disulfide bonds was ascribed to the shielding of these reactive groups by the unreactive peptide chains. 

The reduction of ferricytochrome c by hydrated electrons and by several free radicals has been studied by pulse radiolysis. The reduction of oxidized cytochrome c by [Fe(edta)] - follows first-order kinetics for both protein and reductant, with a rate constant of 2.57 x 10 1 mol" s" at pH 7 and activation enthalpy and entropy of 6.0 kcal mol" and —18 cal K" mol", respectively. These values are comparable to those for outer-sphere cytochrome c reductions and redox reactions involving simple iron complexes, and are compatible with outer-sphere attack of [Fe(edta)] " at the exposed haem edge, although the possibility of adjacent attack through the haem pocket is not ruled out. The rate data at pH 9 are consistent with [Fe(edta)] " reduction of two slowly interconverting forms of the protein, native kt = 2.05 X10 1 mol" S" ) and high-pH kt = 2.67 x 10 1 mol" s" ) isomers. A possible route for the transfer of the electron from Cr + to ferricytochrome c has been suggested as a result of the chemical analysis of the chromium(m) product. The reduction by Cr + of the native protein and of ferricytochrome c carboxy-methylated at the haem-linked methionine (residue 80) has been studied kinetically. At pH 6.5 the former process is simple and corresponds to a second-order rate constant of 1.21 x 10 1 mol" s". The latter, however, is complex - two chromium-... 

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