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The Oxidation of Toluene by Cobalt–Copper–Bromide System. A Side-chain Acetoxylation

1979; Oxford University Press; Volume: 52; Issue: 11 Linguagem: Inglês

10.1246/bcsj.52.3321

1348-0634

Toshihiko Okada, Yoshio Kamiya,

Catalytic Processes in Materials Science

Abstract The liquid-phase oxidation of toluene catalyzed by the cobalt(II) ion and the bromide ion in the presence of the copper(II) ion has been studied. Benzyl acetate was obtained in a good yield (50–70%) with mixed catalysts of metal acetates and sodium bromide in acetic acid at 100–150 °C, accompanied by small amounts of benzaldehyde and benzoic acid. The product distribution was greatly dependent on the NaBr concentration, which can be explained in terms of the high oxidizing ability of the copper(II) ion coordinated by the bromide ion. A synergistic effect was found on the yield of benzyl acetate upon the addition of copper(II) acetate with a high NaBr concentration, the maximum yield being obtained at the Co:Cu:NaBr ratio of 1:1:5–10. A change in the oxygen partial pressure also varied the product distribution, suggesting that the competitive reaction of the copper(II) ion with the oxygen molecule for the benzyl radical was simultaneously taking place at a diffusion-controlled rate. Benzyl acetate was considered to result from the oxidation of the benzyl radical by cop-per(II) bromide and the subsequent solvolysis by acetic acid. The addition of acetic anhydride had a negative effect on the formation of benzyl acetate.