ChemInform Abstract: REDUCTION OF PYRIDINE N‐OXIDES BY TITANIUM(III)

Abstract

The reactions between TiIII and a number of substituted pyridine N-oxides have been studied in a number of acids and have been found to exhibit the stoicheiometry. 2TiIII+ X-pyo + H2O → 2[TiO]2++ X-Hpy++ H+ and to obey the rate law (i). The reactions are suggested to proceed by the stepwise reduction of the pyridine N-oxide by, –d[TiIII]//2dt=k[TiIII][X-pyo]//[H+](i)[Ti(OH)]2+via a free-radical path. The rate constants, which range from 5.6 × 10–4 to 0.75 s–1, are influenced more by the steric and complexation effects of the ring substituents (Br, Cl, Me, OMe, CN, or CO2H) than by their electron-donating or -withdrawing properties.