An induction-detecting ESR spectrometer system, capable of μs time resolution, has been set up, and measurements were made on the radiolytically produced solvated electrons in water, methanol, ethanol, and mixtures of water and these alcohols. The spectrum of the solvated electron was a singlet in all these solvents. The g factor of the hydrated electron was measured to be 2.000 47±0.000 07 at 22 °C in reasonable agreement with the reported data. While this value is significantly smaller than the free electron g factor, the corresponding g factors in methanol and in ethanol, respectively 2.002 05±0.000 07 and 2.001 97±0.000 07 at 22 °C, were found much closer to it. In both methanol–water and ethanol–water mixtures the g factor of the solvated electron varied approximately in proportion to the mole fraction. The g shift of the hydrated electron was interpreted as arising from spin density in the proximity of oxygen nuclei of water molecules. Ab initio MO calculations were performed for an anionic cluster of water and that of methanol, assuming a cavity-like structure. The result showed that while in a water cluster the spin population on oxygen 2p atomic orbitals was in fact significant, the corresponding orbital spin population was smaller in a methanol cluster especially with a dipole-oriented model. The difference was considered to be related to increased diffuseness of the half-occupied orbital in the latter cluster.
to a factor of 10 lower than at pH = pAl(H2P04-) -1.02, proving that H+ determines the overall rate of disappearance at all temperatures.At ambient temperature and up to 100 °C reaction 6 is rate determining with an activation energy of 7.6 ± 0.8 kJ mol-1 (1.8 ± 0.2 kcal mol-1) and a rate constant k6 = (9.6 ± 1.0) X 107 dm3 mol-1 s-1 at 20 °C. These figures are in agreement with reported data.6 78Above 100 °C the rate constant calculated as k6 (Figure 5) increases drastically, and the linearity of the Arrhenius plot in the temperature region °C suggests that a new reaction becomes rate determining. The activation energy determined at these high temperatures is very large, EA = 80 ± 12 kJ mol-1 (19 ± 3 kcal mol-1). From eq V an overall decay rate constant of /c7 = 1.0 X 1010 mol-1 s-1 may be calculated at pH 5.64 and at 285 °C (reactor conditions). At higher pH's the rate constant decreases linearly with the H+ concentration. As a tentative
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