Abstract
Critical phenomena in ethylbenzene oxidation in an acetic acid solution at high cobalt(III) concentrations (from 0.01 to 0.2 mol L−1) were studied at 60–90 °C by the gasometric (O2 absorption), spectrophotometric (CoIII accumulation), and chemiluminescence (relative concentration of radical RO2 ·) methods. These phenomena are as follows: (1) increase in the oxidation rate above the theoretical limiting rate of radical autooxidation (k 3 2[RH]2/2k 6); (2) achievement of a maximum and a sharp decrease in the oxidation rate and concentration of radical RO2 · with the further increase in the CoII concentration (existence of critical concentrations). The oxidation rate increases due to the reaction RO2 · + CoII + H+ → → ROOH + CoIII, while the inhibition effect is caused by the decay of RO2 · radical involving two cobalt(II) atoms: RO2 · + 2 CoII → R′CO + CoIII + CoII (k(70 °C) ≈ 300 L2 mol−2 s−1). The detailed scheme (through the formation of the complex RO2 ·CoII) describing the conjugation of these reactions was proposed.
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Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1823–1827, August, 2005.
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Gavrichkov, A.A., Zakharov, I.V. Critical phenomena in ethylbenzene oxidation in acetic acid solution at high cobalt(II) concentrations. Russ Chem Bull 54, 1878–1882 (2005). https://doi.org/10.1007/s11172-006-0052-2
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DOI: https://doi.org/10.1007/s11172-006-0052-2