K S Rangappa
Articles written in Journal of Chemical Sciences
Volume 113 Issue 4 August 2001 pp 291-296
Histidine as a catalyst in organic synthesis: A facile
H Mallesha K R Ravi Kumar B K Vishu Kumar K Mantelingu K S Rangappa
α, N-diarylnitrones were synthesized by the reduction of a mixture of nitro-and benzaldehyde derivatives with zinc dust using histidine as a catalyst.
Volume 116 Issue 1 January 2004 pp 49-53
M N Kumara D Channe Gowda A Thimme Gowda K S Rangappa
The kinetic of oxidation of dipeptides (DP) namely valyl-glycine (Val-Gly), alanyl-glycine (Ala-Gly) and glycyl-glycine (Gly-Gly), by Mn(III) have been studied in the presence of sulphate ions in acid medium at 26°C. The reaction was followed spectrophotometrically at λmax = 500 nm. A first-order dependence of the rate on both [Mn(III)]o and [DP]o was observed. The rate is independent of the concentration of reduction product, Mn(II) and hydrogen ions. The effects of varying the dielectric constant of the medium and addition of anions such as sulphate, chloride and perchlorate were studied. The activation parameters have been evaluated using Arrhenius and Eyring plots. The oxidation products were isolated and characterized. A mechanism involving the reaction of DP with Mn(III) in the rate-limiting step is suggested. An apparent correlation was noted between the rate of oxidation and the hydrophobicity of these dimers, where increased hyphobicity results in increased rate of oxidation
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