Mechanism of the permanganate oxidation of unsaturated compounds. Part III. Intermediates in the oxidation of maleic and fumaric acids

Abstract

The intermediates in the permanganate oxidation of maleic and fumaric acids have been studied in acidic solutions, The accumulation and decay of manganese(ti1) has been demonstrated by the stopped-flow technique. The concomitant four-electron oxidation of the substrates leads to the formation of forrnyl( hydroxy)acetic acid. The subsequent reactions reveal a complex pattern in which hydroxymalonic. glyoxylic, and oxalic acid are further intermediates. The product distribution has been determined as a function of the pH and the mole ratio of the reactants. A reaction scheme is suggested which rationalises the observed behaviour. Sciences,

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“…The inorganic Mn­(III) disproportionates to Mn­(II) and Mn­(IV) due to the absence of any stabilizing agent in the reaction mixture . Besides, a peak at 486 nm corresponding to Mn­(III) is not observed during the entire oxidation process, − which further supports the finding.…”

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“…This debate was mainly due to the complexity of the reaction intermediates, such as Mn(III), -(IV), -(V) and -(VI) species involved with permanganate reduction (Bose et al, 1991). There have been extensive studies on the mechanisms of permanganate oxidation of various organic compounds, with efforts to identify the reaction intermediates (e.g., Jáky and Simándi, 1972;Jáky et al, 1973;Lee and Brownridge, 1973;Simándi et al, 1977;Bose et al, 1991). Previous studies have shown that short-lived manganese intermediate species were not only very reactive but also subject to disproportionation.…”