Mechanism of peroxide reactions: Kinetics of oxidation of aromatic aldehydes by peroxomonosulfuric acid

Abstract

The kinetics of oxidation of benzaldehyde and <i>p-</i>nitrobenzaldehyde by peroxomonosulfuric acid (PMSA) have been carried out over a wide <i style="mso-bidi-font-style: normal">p</i>H range 0-9.5 at 35°C. The reactions obey second order kinetics, first order each in [PMSA]

and [substrate]. The observed v-shaped <i style="mso-bidi-font-style:normal">p</i>H-rate profile has been rationalised by invoking HSO<img src='http://www.niscair.res.in/jinfo/subscript5.gif' border=0>, SO<img src='http://www.niscair.res.in/jinfo/subscript25.gif' border=0>, the protonated and unprotonated forms of aldehyde as the reactive species, and a suitable rate law has been proposed. The mechanism of oxidation involves rate-determining nucleophilic attack of the peroxo anion on carbonyl-Carbon of the substrate species, followed by hydride ion shift and oxygen-oxygen bond fission to yield the products. The activation parameters of the react ions are reported.

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