The kinetics of oxidation of aromatic anils to benzaldehyde and azobenzene by potassium peroxymonosulfate has been studied in aqueous acetic acid medium. The low dielectric constant of the medium facilitates the reactivity. It has been found that the variation in the ionic strength of the reaction has a negligible effect on the rate. Similarly, polymerization was not observed when acrylonitrile was added to the reaction mixture. This observation rules out the formation of any free radical in the reaction. The added Mn(II) increases the rate of the reaction, which indicates the involvement of two-electron transfer. Highly negative S # values indicate a structured transition state. The deviation of the Hammett plot was noted, and a concave downward curve was obtained for the anils with substituents in the aniline moiety. The observed break in the log k obs versus σ is attributed to the transition state whereas the concave upward curve was observed for the substituents in the benzaldehyde moiety and in the combination of aniline and benzaldehyde moieties, and a suitable mechanism was proposed. C 2013 Wiley Periodicals, Inc. Int J Chem Kinet 45: [542][543][544][545][546][547][548][549][550] 2013
The kinetics of oxidation of 9 meta-and 15 para-substituted aromatic anils by sodium perborate were investigated in aqueous acetic acid medium. The reaction was second order with respect to aromatic anil and first order with respect to the sodium perborate. The increase of [H + ] in this oxidation retards the rate of the reaction. The observed rate constant for the substituents were plotted against the Hammett constant, σ and a non-linear concave downward curve was obtained for the anils with substituents in the aniline moiety. The observed break in the log kobs versus σ was attributed to the transition state whereas the non-linear concave upward curve was observed for the substituents in the benzaldehyde moiety and a non-linear concave upward curve was observed for the substituents in the combination of aniline and benzaldehyde moiety. The electron withdrawing substituents fall on one side of the curve, having a negative ρ value and the electron releasing substituents fall on the other side, with a positive ρ value and a suitable mechanism was proposed.
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