Kinetics of oxidation of glyoxylic and pyruvic acids by vanadium(V)

Oxidation of hydroxyurea with oxovanadium(V) ions in acidic aqueous solution

“…In terms of the MO bonding scheme, the higher acidity of the V V O(OH) 2+ ion could be accounted for by a higher basicity of the hydroxo than the oxo ligand, due to involvement of the oxo 2p orbitals in p-bonding that leaves only the non-bonding sp r hybrid for protonation. It should be noted that our pK a value compares poorly with a value that can be calculated from the Sen Gupta and Chatterjee kinetic and thermodynamic data reported for oxidation of glyoxylic and pyruvic acids (pK a = +0.8) [46]. However, their reported value seems to be too high; otherwise it certainly would not have escaped to be noticed in the numerous potentiometric titration studies performed so far.…”

“…It seems worth to mention that the formation of a complex analogous to V V O(OH)U + was reported for thiourea [43], but the value of its stability constant was not reported. Although complexes with the protonated form of cisdioxovanadium (OV V OH) were reported [44,45], and the protonation of V V O þ 2 in strong acid was proposed on several occasions [37,46], no direct physical evidence to support the hypothesis has been provided so far. Begun and coworkers [47] have studied protonation of V V O þ 2 in concentrated perchloric acid, but they proposed formation of a dimeric protonated V V species, i.e.…”

Evidence for the Distinct Vanadyl(+4)-Dependent Activating System for Manifesting Insulin-Like Effects

“…Reduction of Vanadate(+5) to Vanadyl(+4) was determined spectroscopically at 765 nm by the appearance of the characteristic "blue" absorbance of the vanadyl(+4) ion following reduction. Samples were acidified to 0.2 M HCl prior to determining absorbance intensity, using an absorption coefficient of 14 ( 0.1 (Gupta & Chatterjee, 1978).…”

Kinetics of oxidation of pyruvic acid by [ethylenebis(biguanide)]silver(III) in aqueous acidic media

“…We, in this report, describe the kinetics * Author for correspondence and mechanism of pyruvate oxidation by the silver(III) complex under reference. We found kinetic evidence that the title complex oxidises glyoxylic acid by a two step one-electron transfer process [5], and thus we thought it worthwhile to oxidise pyruvic acid by the silver(III) complex to substantiate (or, compare) the mechanistic aspects of electron transfer as glyoxylic acid and pyruvic acid are in many ways kinetically comparable in their oxidations [15][16][17].…”

“…Mechanistic studies on pyruvate oxidation by highervalent metals are not very common [15][16][17][18][19]. Silver(III) in the title complex is much stabilised by the acyclic tetraaza ligand and is inert to substitution (d 8 ).…”