NOTES
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Since the effective energy of interaction of a polar and a nonpolar molecule has the same form as that between two nonpolar molecules14 the polarity of one component does not alone cause deviations in mixed systems. For example, water vapor diffusion coefficients with simple nonpolar gases conform to the corresponding states norm.13 This suggests that corresponding states deviations in mixed diffusion data are wholely due to the effect of molecular shape provided that one component is a simple nonpolar gas. Some tendency may, in fact, be discerned in the sequence observed in the present work for deviations to become more marked with departure from spherical shape of the polar component, the nitromethane results being closest to normal behavior. Large negative deviations have also been observed in mixed diffusion with C6-CS hydrocarbons6 where polar influences are absent. These results suggest, therefore, that kinetic theory models which include a molecular shape factor will prove more successful in treating the class of polar molecules discussed than will the (12 :6 :3) potential model. (14) J. 0.Hirschfelder, C. F. Curtiss, and R. B. Bird, “Molecular Theory of Gases and Liquids,” John Wiley and Sons, Inc., New York, N. Y., 1954, p 987.
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I
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Aromatic Amines in Benzene by T. J. Kemp, J. P. Roberts, School of Molecular Sciences, University of Warwick, Coventry, United Kingdom
G. A. Salmon, and G. F. Thompson University of Leeds, Cookridge High Energy Radiation Research Centre, Cookr&e Hospital, Leeds 16, Yorkshire, United Kingdom Accepted and Transmitted by The Faraday Society (December 7 , 19t!S)
Although pulse radiolysis has been used extensively to determine the spectra and reactions of the solvated electron and of the species formed on neutralization of the corresponding counterion, e.g., CeHll. in cyclohexane,’ few studies have been reported of the fate of the counterion before neutralization. Keene, et U Z . , ~ observed small yields (G 0.3) of a species absorbing with a spectrum corresponding to the amine radical cation on pulsing dilute solutions of certain amines in
-
The Journal of Physical Chemistry
6000
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Wavelength, A .
Figure 1. End-of-pulse spectra of solutions in benzene of TPA (right) (1.02 X 10+ M ) and TMPD (left) (1.05 X M) (solid lines). The broken lines correspond to the radical cations T P A . + at - 196’ [D. W. Skelly and W. H. Hamill, J. Chem. Phys., 43, 3497 (1965)l and T M P D * + at room temperatureeJ
cyclohexane. This results presumably from the charge exchange (1b) (where R H = hydrocarbon)
RH --+ R H . +
+ A+RH e- + A s + +
RH.+
Pulse Radiolysis of Solutions of Tertiary
(
7000
+ e+A.+ A
(14 (1b) (2)
We have performed the pulse radiolysis of deaerated ~ 1 0 - *M solutions of triphenylamine (TPA) and N, N, N’, N’-tetramethyl-p-phenylenediamine (TMPD) in benzene. Intense absorptions closely resembling those of the corresponding radical cation mere produced (Figure 1). Similar but less intense absorptions were obtained from solutions of the amines in cyclohexane, dimethyl sulfoxide, and dioxane. Almost no absorption was produced from a diethyl ether solution. Accordingly, solutions in benzene were subjected to a special examination from which the following features emerged. (i) At low doses (
