The reaction of hydroxyl radicals with benzene in aerated aqueous solutions under y radiolysis produces phenol and ß-hydroxymucondialdehyde (ß ). The respective G values are 1.7 and 1.2, in 0.8 N H2SO4, and 1.78 and 0.7, in neutral solutions, the sum of the two yields accounting for all the OH radicals in each instance. The enhancing effect of ferrous ions on these yields has been correlated with the peroxide chain mechanism advanced originally to account for the influence of organic impurities on the (?(Fe3+) of the Fricke dosimeter. At a benzene concentration of 10~2 M and a ferrous ion concentration of 10-3 M, G(Fe3+) is ~48;(7(phenol) and (7(ß ) are 8.8 and 6.6, respectively. This corresponds to a chain length of ~2.

No abstract

No abstract

Quantitative estimation of OH by measuring its reaction with benzene in the presence of oxygen to give phenol and hydroxymucondialdehyde (HMD) shows that in the photolysis of hydrogen peroxide at 2970-3650 Á OH radicals account for all the primary decomposition. In the photolytic reduction of Fe3+ in water, the average quantum yield of OH for 2970-4358 Á is ~0.02, of the same order of magnitude as the earlier estimate of the Fe2+ yield for 2537 Á. The oxidation of benzene to phenol by Cu2+, in contrast, yields no HMD, and must be by oxygen uptake not involving an OH intermediate. Inner filter corrections are deduced for the accumulation of product interfering with light absorption.

Publication costs borne completely by The Journal of Physical Chemistry G(-Ce4+) in the aqueous ceric sulfate system is constant in the region 0-30°and thereafter drops steadily, whereas G(Fe8+) in the deaerated ferrous sulfate system remains strictly constant at 8.1 ± 0.05 from 0 to 120°. From this it follows rigorously that (?(OH) is constant at least from 0 to 30°. This fact makes it possible to identify the formation, in addition to phenol, of two aldehydes in the y radiolysis of the aerated neutral aqueous benzene system and to characterize them as the a and ß isomers of hydroxymucondialdehyde (HMD). The sum of the yields of the three products is equal to G(OH). From 40°u pward C?(phenol) rises sharply and reaches a value of ~5 at 220°. At 60°and above the HMD appears to be replaced by ketonic products from fragmentation of the benzene ring. An analysis of the temperature coefficient of (?(Fe3+) of the aerated Fricke system suggests that it is in the main due to a competition between two reactions, + 02 -* HO2 and H2+ + Fe2+ -* H2 + Fe3+. The anomaly noticed at the higher temperatures in the ceric and aqueous benzene systems is interpreted as evidence of onset of oxidizing action of 02. Adverse consequences of this study for the diffusion theory of radiolysis are discussed.