Kinetics of oxidation of thiocyanate ion by manganese(III) in pyrophosphate medium

Abstract

Mn m is stabilized by pyrophosphate in weakly acidic solutions. The nature of the complex formed was elucidated spectrophotometrically. The kinetics of Mn m oxidation of thiocyanate in pyrophosphate medium was investigated over the pH range 2-3. The oxidation followed first order kinetics with [Mnm]. The effects of varying [Mn'H], [NCS-], added Mn" and metal ions, pH, total [P2Ov 4-] and added C10~, C1-and SO 2-were studied. The order in [NCS-] was unity, and increasing [H +] increased the rate. Retardations with added P20~ -and Mn" were observed. Complexation of NCS-as KEZn(NCS)r decreased the reactivity without any change in overall mechanism. The dependence of the reaction rate on temperature was examined, and activation parameters were computed from Arrhenius and Eyring plots. A mechanism consistent with the results is proposed.

Influence of Pyrophosphate on the Generation of Soluble Mn(III) from Reactions Involving Mn Oxides and Mn(VII)

“…The shorter lag phase at pH 9.0 in our experiments compared to the literature should be attributed to different solution matrix and disproportionation conditions . Alhough Mn­(III)-PP at pH 5.0 and 6.0 was stable within 10 min, the generation of Mn­(III)-PP at pH 5.0 and 6.0 was less compared to that at pH 7.0 and 8.0, which may be due to the higher reactivity of Mn­(III)-PP with reductant at lower pH since no MnO 2 was generated at pH 5.0 and 6.0. , Although no disproportionation of Mn­(III)-PP was observed at pH 5.0 within 10 min, the disproportionation of generated Mn­(III)-PP started after 30 min and reached equilibrium in about 8 h, as demonstrated in Figure S13.…”

Oxidation of L‐aspartic acid and L‐glutamic acid by manganese(III) ions in aqueous sulphuric acid, acetic acid, and pyrophosphate media: A kinetic study

“…Solution of manganese(II1) acetate, in aqueous acetic acid medium, was prepared by electrolytic oxidation of manganese(I1) acetate as described previously [9]. It was observed that 0.01 mol dm-3 manganese(II1) acetate solution was stable for three days in aqueous acetic acid medium (75% v/v).…”

Oxidation of L-glutamine by manganese(iii) in aqueous sulfuric acid, acetic acid, and pyrophosphate media: A kinetic and mechanistic study

“…A known amount of L-glutamine was allowed to react completely with 2 -4 fold mole excess of manganese(III) in the presence of excess manganese(II) in a proper medium and temperature (1.50 (-ࠗ-ࠗ-), 2.00 (-⌬-⌬-), 4.00 (-ٗ-ٗ-), 6.00 (-ϫ-ϫ-), and HOAc; mol and (C) Pyrophosphate medium: 4.00 (-ٗ-ٗ-), 6.00 (-ϫ-ϫ-), and 8.00 [Na P O ] ϭ 1.00 ϫ 10 dm ; pH 1.3; Temp. ϭ 328 K. 4 2 7 was determined by iodometric titration with a standard sodium thiosulfate solution using starch indicator near the end point.…”