α-nucleophiles as the basis of organized supernucleophilic microheterogeneous systems for the destruction of organophosphorus compounds

Abstract

Peroxyhydrolysis of 4-nitrophenyl esters of phosphoric and phosphonic acids has been studied in organized microheterogeneous systems based on dimeric cationic imidazole-containing surfactants (AlkIm⁺-(CH₂)_m-Im⁺Alk ∙ 2Br^- , m = 2,3,4, Alk = C₁₂H₂₅, C₁₄H₂₉). Micellar effects of the surfactants (at pH = const and [surfactant]0 = const) reach ~ 10–100 times. Physicochemical parameters of the peroxyhydrolysis process (such as substrate binding constants, hydroperoxide anion nucleophilicity in micellar pseudophase) are described in terms of the pseudophase distribution model. Observed rate enhancement mainly depends on reagent concentration increasing directly connected to hydrophobicity of the substrate and surfactant. Changes of HOO^- nucleophilicity under the displacement of the peroxyhydrolysis from water to surfactant micelles also contributed to the micellar effects. Comparative analysis of the regularities of peroxyhydrolysis and alkaline hydrolysis testifies for generality of such features in OMS for nucleophilic substitutions. In this regard, the α-effect as rate constants ratio of peroxyhydrolysis (𝑘^m_{2,𝐻𝑂𝑂}−) to base hydrolysis (𝑘^m_2,𝐻𝑂−) in micellar pseudophase (𝑘^m_{2,𝐻𝑂𝑂}−/𝑘^m_2,𝐻𝑂−) reaches ~ 80–100 times.

Therefore, the α-effect appears not only in water, but in OMS, too.