The Arrhenius parameters for the two-site jumping of the potassium cation in p-beiuosemiquinone ion pairs in DME have been determined by comparing computed line width and line amplitude ratios with those derived from experimental spectra over the temperature range -10 to f90"C.The results were E = 3-4f 1 kcaI mole-1 and log,,A = 9.5 10.5. The A factor indicates a negative entropy of activation for the intramolecular process and this is discussed. A study of two-site jumping of alkali metal ions in 2,5-di-tert butyl p-benzosemiquinone ion pairs in DME has been described. The rate of jumping increases along the series N a t K< Rb. An approximate value for the activation energy of the process has been determined for the potassium derivative.
An extrapolation method is described for the determination of the extinction coefficients of free radical anions and di-anions in ether solution. The method avoids the errors inherent in conventional methods and which could be considerable for those anions which must be handled in uacuo. It is applicable where, because of the equilibrium between radical anion and di-anion and generator, it is not possible experimentally to prepare a solution which comprises 100 % radical anion. Results for sodium benzophenone and sodium p-phenyl benzophenone in dioxan are given and discussed. The general applicability of the method is also discussed.
The freeradical-anions af ct,y-diphenylbutadiene, diphenyldiacetylene, tetraphenylethylene, tetraphenylbutatriene, tetraphenylhexapentaene, dibiphenylene-ethylene and dibiphenylenebutratriene have been produced in solution by reduction with potassium. Well-resolved e.s.r. spectra of the radical-anions have been recorded. Except for tetraphenylethylene the spectra have been completely analyzed and the experimental h.f.s.c. compared with the values calculated by the Huckel and McLachlan methods. For tetraphenylethylene, partial analysis of the spectrum has been achieved and two h.f.s.c. and the total spectrum width have been determined. All attempts to produce the freeradical-anion of tetraphenylallene failed. This has been discussed in terms of the probable electron-affinity of this molecule.Electron spin resonance (e.s.r.) spectrometry has been extensively applied to the determination of isotropic proton hyperfine splitting constants (h.f.s.c.
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