The reactivity of hydroxide and peroxide anions with 4-nitrophenyl N,N-dimethylcarbamate in aqueous-alcoholic detergent media and in "oil in water" microemulsions has been studied. Aqueous-alcoholic solutions of cationic (CTAB) and neutral (Triton X-100) surface active substances have promise for decomposition of substrates by a nucleophilic mechanism.The dual nature of hydrogen peroxide, as a highly reactive nucleophile as the HOO -anion and as a mild oxidant in the neutral form (H 2 O 2 ), permits the description of this reagent as a universal degassing system [1][2][3]. However, the high hydrophilicity of hydrogen peroxide, coupled with the hydrophobicity of ecotoxicant substrates, imposes a basic requirement of a medium which should facilitate interaction by both oxidative an nucleophilic mechanisms. To overcome the barrier of mutual insolubility of the reagents it is possible to carry out reactions in supramolecular polycomponent systems: microemulsions (ME), micelles of various types, and aqueous-ethanolic mixtures [4,5].Despite the attractiveness of ME as media with high solubilizing properties, their use on a large scale is coupled with a number of disadvantages. In the first place, ME are usually multicomponent systems. Even the simplest ME contain four components -a detergent, a co-detergent, oil, and water [4], and to solve specific applications the composition of an ME may contain up to ten components [3]. The necessary presence of oil in the microemulsion medium results from its ability to dissolve toxic organic solvents (e.g., saturated hydrocarbons and their halogen derivatives [4]), considerably decreases the ecological safety of the reaction media. Secondly, it is not unimportant that nucleophilic reactions in ME occur at a lower rate [3] than analogous processes in water, aqueous-alcoholic and micellar systems. Whereas one of the known [5] principal requirements required in detoxication systems is a high rate of chemical conversions.In the present work a comparative estimate of the reactivity of hydroxide and peroxide anions in microemulsions and in ethanol/water/detergent systems using the decomposition of 4-nitrophenyl N,N-dimethylcarbamate as an example:We chose 4-nitrophenyl N,N-dimethylcarbamate (I) as a model substrate because its reactivity with respect to HO -and HOOanions in water and aqueous-ethanol mixtures had been studied previously [5].

The acid-base equilibrium of hydrogen peroxide in aqueous solutions of CTAB and the reactivity of the peroxide anion toward 4-nitrophenyl diethylphosphate and 4-toluenesulfonate were studied. It was shown that the acid ionization rate constant of hydrogen peroxide is increased by three times with increase in the CTAB concentration from 0 to 0.03 M. This makes it possible to realize the decomposition of the substrates by their reaction with the peroxide anion at lower pH values in micellar cationic systems than in aqueous solutions.Previously it was shown that hydrogen peroxide can be recommended as a universal agent in the creation of "soft" and ecologically safe decontamination systems by virtue of its dual nature (an effective oxidizing agent with respect to the analogs of yperite [1] and a reactive a-nucleophile in nucleophilic substitution in organophosphorus esters [2]).Two circumstances must be numbered among the substantial limitations to the simultaneous disintegration of ecological toxicant substrates by the oxidation and nucleophilic substitution pathways. First, hydrophobic substrates have extremely low solubility in the aqueous media that are the most favorable with respect to the requirements of "green" technologies and to the reactivity of H 2 O 2 as oxidant [3] and HOO -as a-nucleophile [2]. Second, the oxidative processes, particularly in the presence of activators, take place at highest rates in the range of pH 8.0-9.0. The successful realization of nucleophilic reactions with the HOO -ion requires the use of more alkaline media, since the ionization constant of hydrogen peroxide pK a = 11.6 [2, 4], i.e., at pH 8.0-9.0 only 0.03-0.3 % of the hydrogen peroxide is in the ionic reactive form HOO -.The use of a micellar system based on cetyltrimethylammonium bromide (CTAB) gives a catalytic effect in the oxidation of thioanisole (a model of yperite) in the H 2 O 2 /HCO 3 − system [1]. There are also examples of the use of HOO -as active nucleophilic agent in the dephosphorylation of 4-nitrophenyl diphenylphosphonate in the presence of cationic detergents [4]. It was established that the main factor affecting the appearance of micellar catalysis in both cases is concentration of the reagents on the surface of the micelle as a result of electrostatic and hydrophobic interactions [4,5]. In addition, the reaction can be further accelerated as a result of displacement of the apparent pK a value of the ionic reagent in the presence of the micelles [6,7]. In connection with this the effect of surfactants on the pK a values of the ionic reagents and also on the distribution of the reaction participants between water and the micellar phase and, accordingly, on the variation of the nucleophilic substitution rate is of some scientific interest.84 0040-5760/08/4402-0084