Uncatalyzed non-Malapradian periodate oxidation of aromatic amines – An overview
R. D. Kaushik, Jaspal Singh, Manila, Priyanka Tyagi, Prabha Singh
Department of Chemistry, Gurukul Kangri University, Hardwar-249 404, Uttarakhand, India E-mail : firstname.lastname@example.org Department of Chemistry, D. A. V. (P.G.) College, Muzaffarnagar, Uttar Pradesh, India Manuscript received 15 December 2013, accepted 15 January 2014 A review of the literature related to the uncatalyzed oxidation of aromatic amines by periodate ion under different conditions is presented. The reports are available from synthesis as well as kinetic point of view. The reports
... re contradictory in terms of the free radical or ion-dipole mechanism and linear free energy relationships (LFERs) reported for this reaction series. In this article, an attempt has been made to make the final picture of these non-Malapradian oxidation reactions clear. The kinetic features and applicability of LFERs as well as isokinetic relationship have been discussed. LFER studies indicate the stabilization of positive charge on the aniline nitrogen by resonance and that the transition state formed should be with a considerable positive charge. The reactions are first order in oxidant and substrate and get influenced by ionic strength and dielectric constant of the medium. The reactions are characterized by the formation of many intermediates which finally give the benzoquinones i.e. main product. One mol of substrate consumes two moles of periodate in the initial part of most of the reactions. High negative value of entropy of activation is another feature of these reactions which indicates the involvement of solvent interactions in these reactions. Special pH effect has been reported and the rate-pH profile shows a maxima which is characteristic of the aromatic amine oxidized. Rate law explaining the effect of pH and formation of intermediates and the isolated products has been proposed. Gross mechanism and the molecular mechanism have been proposed on the basis of the kinetic features, LFER studies and the identified reaction products.