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|Title:||Oxovanadium(lV)-catalysed and uncatalysed acid bromate oxidation of mandelic acid|
|Authors:||Reddy, Ch Sanjeeva|
Kumar, T Vijaya
|Abstract:||The oxidation of mandelic acid (MA) by bromate in acidic aqueous solutions exhibits first order each in [Br(V)], [substrate] and second order in [H2SO4.]. The reaction exhibits an inverse solvent effect (kD2O / kH20 =0.66 at 313K) and no primary isotope effect. The mechanism consists of rate determining esterfication of mandelic acid with H2BO3, followed by a fast disproportionation of the ester through C-C bond cleavage to form benzaldehyde. Oxovanadium(IV)-catalysed Br(V) oxidation of the substrate in perchloric acid medium exhibits first order each in [MA], [VOSO4] and is independent of [oxidant]. The hydride ion-abstration mechanism is proposed to account for the oxovanadium(IV)-catalysed reaction. The rate law is given by -d[Br(V)]/dt=k[MA][V(IV)]=ko The activation parameters of catalysed and uncatalysed reactions are evaluated and discussed.|
|Appears in Collections:||IJC-A Vol.37A(10) [October 1998]|
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