22 research outputs found
Metal catalysis in oxidation by peroxides. Part 5. On the mechanism of vanadium(V) catalysed oxidation by hydrogen peroxide
Cyclic sulphoxides as ligandsâIXX. Adducts of lanthanide iodides and thioxane-oxide (TSO)
Cyclic sulphoxides as ligandsâXVI. Adducts of lanthanide perrhenates and thioxane-oxide (TSO)
Complexes of lanthanide methanesulphonates with thioxane oxide: Comparison with tetramethylene sulphoxide
Borate catalysed reactions of Hydrogen peroxide: kinetics and mechanism of the oxidation of organic sulfides by peroxoborates
The kinetics of the oxidation of substituted phenyl methyl sulfides by hydrogen peroxide in borate/boric acid buffers were investigated as a function of pH, total peroxide concentration, and total boron concentration. Second-order rate constants at 25â°C for the reaction of methyl 4-nitrophenyl sulfide and H2O2, monoperoxoborate, HOOB(OH)3â, or diperoxoborate, (HOO)2B(OH)2â, are 8.29Ă10â5, 1.51Ă10â2 and 1.06Ă10â2âmâ1âsâ1, respectively. Peroxoboric acid, HOOB(OH)2, is unreactive. The Hammett Ï values for the reactions of a range of substituted phenyl methyl sulfides and hydrogen peroxide, monoperoxoborate or diperoxoborate are â1.50±0.1, â0.65±0.07 and â0.48 (two points only), respectively. The Ï values for the peroxoborates are of significantly lower magnitude than expected from their reactivity compared to other peroxides. Nevertheless the negative Ï values indicate positive charge development on the sulfur atom in the transition state consistent with nucleophilic attack by the organic sulfides on the peroxoborates as with the other peroxides. The kinetic parameters, including the lack of reactivity of peroxoboric acid, are discussed in terms of the differences in the transition state of reactions involving peroxoboron species with respect to those of other peroxides