Micellar effects on Cl2.-reactivity. Reactions with surfactants and pyrimidines

Abstract

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 . -

Free Radical Reactions Involving Cl•, Cl2-•, and SO4-•in the 248 nm Photolysis of Aqueous Solutions Containing S2O82-and Cl-

“…When the chloride concentration is relatively high, Cl 2 -• molar concentration is relatively large and the second-order contribution to the overall loss of Cl 2 -• becomes more important. Most previous studies of the second-order decay of Cl 2 -• are focused on reaction 9. ,,,,,,,,,,,− We find that varies as Cl - molar concentration changes. When equilibrium 3 is maintained, reaction 10 is assumed to be important.…”

A laser flash photolysis kinetic study of reactions of the Cl2? radical anion with oxygenated hydrocarbons in aqueous solution

“…In comparing these data, it needs to be noted that the majority of the previous studies have not been performed in dilute solutions but rather at moderate ionic strength (I ϭ 1 M). Only for reaction (7) with 2-propanol previous investigations in dilute aqueous solution have been performed. The rate constant from the present work is in good agreement, within the experimental errors, with previous data obtained from both laser photolysis [29] and pulse radiolysis studies [10].…”

“…The results are summarized in a review by Neta et al [5]. Several pulse radiolysis studies have been performed including reactions of Cl 2 Ϫ with nucleic acid constituents [6], surfactants and pyrimidines [7], amino acids [8], and organic nucleophiles [9]. Moreover, in order to elucidate the mechanism of electron transfer reactions of Cl 2 Ϫ , Storer et al [10], Lierse et al [11] and Gogolev et al [12] studied reactions with platinum coordination compounds, selected actinides, and complexes of the transition metal ions Co(II), Fe(II), and Mn(II), respectively.…”

Rate constants of dichloride radical anion reactions with molecules of environmental interest in aqueous solution: a review

“…The molecule has 14 -CH 2 -units, therefore, many possibilities for H-abstraction. The rate constant, 1.2 × 10 7 M -1 s -1 , is much higher than that of the previously mentioned trialkylammonium ions (Patterson et al 1972). In vinyltrimethylammonium chloride, the reaction takes place on the styrene part of the molecule forming radical cation (2.3 × 10 8 M -1 s -1 , Kumar et al 2003).…”

“…Table 7 lists also the rate constant of the cationic surfactant sodium dodecyl sulfate (NaLS) and the neutral nonylphenol ethoxylate (Igepal CO-730) surfactant (3.9 × 10 6 and 2.1 × 10 8 M -1 s -1 , respectively, Patterson et al 1972 ). The k Cl2•- for the latter is much higher due to the presence of the –O-CH- moiety, the rate constant is similar to that of anisole, 1.62±0.09 × 10 8 M -1 s -1 (Lei et al 2019 ).…”