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Reactivities of C12.-with micelle-forming surfactants and with uracil, 5-chlorouracil, thymine, cytosine, and cytidine both in aqueous and micellar systems have been investigated. Rate constants for initial reactions of C h -with surfactants and with these pyrimidines have been measured by pulse radiolysis where possible. Steady-state studies of competition between pyrimidines and surfactants for Clz, -were carried out by determination of G(-pyrimidine) following CO-60 y-cell irradiation. It has been shown by combining data from these two methods that kc,?, -+ is smaller above the critical micelle concentration than below it. Although little or no micellar effect is observed on the initial reaction between CL.-and uracil or its derivatives (thymine and 5-chlorouracil), it is evident that there is interference which in subsequent processes lowers G( -pyrimidine). In cytosine and cytidine systems some initial effects are evident at concentrations of these compounds of about 5 X loFa M . In addition, G( -cytosine) and G( -cytidine), in the presence of micellar hexadecyltrimethylammonium chloride, are greater than in the presence of monomeric surfactant.h e presence of chloride ions in irradiated acidic air-T saturated aqueous solutions has been shown t o increase the base destruction yields of uracil a n d cytosine, to have no effect on those for thymine, a n d to decrease those for nucleotides and nucleosides. 4--7 y irradiation of aqueous air-saturated acidic sodium chloride solutions results in the following p r o c e s s e~.~~~ H20 -w + esq-+ .H + .OH + Hz + H202 (1). H + 0 2 HOz (3) (4) c1. + c1-+ a n . -

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