Kinetics of the borate anion catalyzed oxidation of diethyl sulfide with hydrogen peroxide in an i-PrOH–H2O medium

Abstract

The problem of creating new reagents for the rapid and selective decomposition of thioethers -active components in pesticides and toxic substances -includes the solution of two basic problems: substitution of the wide use for utilization of sulfides of toxic derivatives of hypochlorous acid and the choice of solvents capable of increasing the solubility of organic sulfides poorly soluble in water, while maintaining the high rate of their oxidation.One of the ways to solve the first problem is the use of oxidizing systems based on hydrogen peroxide, which is the ecologically pure oxidant and fulfils the current requirement for "green" technology. However it is less effective than derivatives of hypochlorous acid in the decomposition of thioethers. One method for the activation of hydrogen peroxide is its conversion into peroxoacids with the use of such activators as bicarbonates [1, 2], silicates [3], molybdates [4,5], nitrites [6] and other compounds.It has been shown recently [7,8] that boric acid, B(OH) 3 , is an effective catalysts for the oxidation of thioethers with hydrogen peroxide in aqueous solutions. The catalytic effect of B(OH) 3 is quantitatively explained by a mechanism which includes the intermediate equilibrium formation of the anions of monoperoxoborate B(OH) 3 (OOH) -(MPB) and diperoxoborate B(OH) 2 (OOH) 2 -(DPB) according to the equations:

Quantum-chemical investigation of the mechanisms of oxidation of dimethyl sulfide by hydrogen peroxide and peroxoborates

“…In solutions in i-PrOH-H 2 O (30 : 70 vol.%) MPB and DPB are four and 100 times respectively more active than H 2 O 2 in the oxidation of Et 2 S[14].Using the values of the activation barriers obtained in the present work for the reactions of dimethyl sulfide with hydrogen peroxide (TS1-H 2 O 2 ), monoperoxoborate (TS2-MPB), and diperoxoborate (TS2-DPB) by means of the the theoretical ratios of the rate constants for the reactions of (CH 3 ) (equal to 1 : 4 : 80). These ratios practically coincide with the experimental value for the oxidation reactions of Et 2 S and accurately confer the increase in the activity of the particles in the order H 2 O 2 < B(OOH)(OH)3 -< B(OOH)…”

“…An effective activator may be boric acid, B(OH) 3 , which in reaction with hydrogen peroxide gives peroxoborates [12]. Recently we showed [13,14] that the monoperoxoborate B(OOH)(OH) 3 -(MPB) and diperoxoborate B(OOH) (OH) 2 2-anions formed at pH 6-13.5 are 2.5 and 100 times respectively more active than hydrogen peroxide in the oxidation of diethyl sulfide.2 0040-5760/11/4701-0002 …”