The oxidation of organic sulfides (thioethers) plays an important role in biochemical transformations and in the chemistry of the atmosphere and natural waters. Dimethyl sulfide (Me 2 S), generated by oceanic phytoplankton, is an important source of sulfur in the atmosphere [1,2]. Its oxidation in the gas phase to the oxides of sulfur leads to the formation of acid rain [2]. In biosystems the oxidation of methionine, which plays a key role in the transfer of unpaired electrons, leads to the destruction of proteins and peptides [3]. Sulfides are also active components of pesticides and toxic substances the utilization of which requires a search for new effective oxidizing systems.Particularly attractive among the large number of the various reagents used for the oxidation of sulfides [2, 4], both in economic and ecological respects, is hydrogen peroxide. The mechanisms of oxidation of thioethers, particularly dimethyl sulfide, by hydrogen peroxide have been studied well experimentally [2, 5, 6] and by quantum-chemical methods [7,8]. The ab initio calculations in [8] indicate that the slow stage of the reaction includes cleavage of the O-O bond in H 2 O 2 and the formation of an S-O bond.However, the oxidation of sulfides by hydrogen peroxide takes place slowly. One promising way of activating H 2 O 2 is to convert it into peroxo acids [9][10][11]. 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

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:

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