The kinetics of chlorination of benzene with a mixture of sodium peroxide with hydrochloric acid in aqueous acetic acid at 298 K was studied. The chlorination rate is the highest when the AcOH concentration in the binary solvent is 49.4 3 40.6 mol % and the ratio of the initial cocentrations of water and sodium peroxide, 18.5320.2. The linear dependences of log k app on the AcOH concentration and [H 2 O] 0 / [Na 2 O 2 ] 0 ratio were obtained. Arenes are usually chlorinated by a direct reaction of molecular chlorine with an aromatic compound. Another procedure used in production of chlorobenzene is high-temperature oxidative chlorination of benzene with chlorine generated by catalytic oxidation of HCl with oxygen [1]. However, the low-temperature (at 2733353 K) oxidative halogenation with hydrohalic acids and hydrogen peroxide (or metal peroxides) is studied insufficiently. As shown in [239], low-temperature halogenation allows preparation of chloro-and bromotoluenes, monochloro-p-xylene, 1-bromonaphthalene, and other compounds in fairly high yields without using toxic molecular halogens.Taking into account the urgency of theoretical studies of oxidative halogenation, in this study we examined the solvent effect on the kinetics of the benzene chlorination in the system Na 2 O 2 3HCl3AcOH3 H 2 O. The simplified scheme of the process includes reactions (I)3(III):C 6 H 6 + Cl 2 76 C 6 H 5 Cl + HCl.
(III)The experiment was performed at 298 K in aqueous AcOH of various concentrations. The reactant ratio C 6 H 6 : Na 2 O 2 : HCl was 1 : 1 : (4 35). The benzene3chlorobenzene mixtures obtained were analyzed by GLC. Preliminary experiments showed that, under the experimental conditions, the yield of benzene dichlorination products was insignificant.As in [10], the reaction rate is satisfactorily described by a second-order reaction equation. Table 1 shows that, as the AcOH concentration (N AcOH ) in the binary solvent AcOH3H 2 O is decreased from 91.9 to 40.6 mol %, k app increases (run nos. 137 in Table 1). A similar trend was observed in chlorination with molecular chlorine of benzene in trifluoroacetic acid [11] and of toluene in acetic acid [12].In the N AcOH range from 4.06 to 91.9 mol %, linear correlation (1) is valid (r 3 0.989): log k app = 3(2.33 + 0.11) 3 (2.36 + 0.14)N AcOH /100. (1) At N AcOH < 40.6 mol %, the constants decrease, and correlation (1) is no longer observed (Fig. 1).Since, according to reactions (I) and (II), under the experimental conditions [Na 2 O 2 ] 0 corresponds to [Cl 2 ] 0 and the chlorinating power of the system H 2 O 2 3HCl depends on the water concentration in the reaction mixture, decreasing with an increase in [H 2 O] [4], it could be expected that the ratio of the initial H 2 O and Na 2 O 2 concentrations q would affect the rate constant more significantly than does the AcOH concentration in the binary solvent. Indeed, in run nos. 7 and 12 (Table 1), at virtually equal N AcOH (40.6 and 40.2 mol %), the rate constants are essentially different. In run nos. 15 and 16, at equal q (40...
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