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Oxidation of glyoxylic acid by a mononuclear manganese(IV) complex of 1,8-bis(2-hydroxybenzamido)-3,6-diazaoctane: A kinetics and mechanistic study |
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| Authors: | Suprava Nayak Gouri S. BrahmaK. Venugopal Reddy K. Veera ReddyAnadi C. Dash |
| Affiliation: | a Department of Chemistry, Osmania University, Hyderabad 500007, India b Faculty of Science and Technology, ICFAI University, Dehradun 248197, India c Department of Chemistry, Utkal University, Bhubaneswar 751004, India |
| Abstract: | The oxidation of glyoxylic acid (HGl) by MnIVL {L4− = tetra deprotonated 1,8-bis(2-hydroxybenzamido)-3,6-diazaoctane} was investigated in the pH range 1.67-10.18, at 25-45 °C and 0.5 M ionic strength. The reaction exhibited biphasic kinetics with MnIIIL− as the reactive intermediate. MnIV was reduced to MnII. The products of oxidation of HGl were identified as formic acid and CO2 in acidic medium, and oxalate in basic medium, consistent with the stoichiometry: −Δ[MnIV]/−Δ[HGl] = 1. In acidic medium, both MnIVL and MnIIIL− formed outer-sphere adducts with the neutral HGl {HC(OH)2COOH} molecule, with an association constant Qav of 28 and 70 M−1, respectively. A similar adduct formation was not observed for the glyoxylate mono anion {Gl−, CH(OH)2(CO2−)} and glyoxylate dianion {Gl2−, CH(OH)(O−)CO2−}. The rate and activation parameters for the various paths are reported and an outer-sphere electron transfer mechanism is suggested. |
| Keywords: | Kinetics Manganese(IV) 1,8-Bis(2-hydroxybenzamido)-3,6-diazaoctane Glyoxylic acid |
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