Процессы «turnover» в реакциях разложения ацилсодержащих субстратов в организованных микрогетерогенных системах

Abstract

Design of organized microheterogeneous systems for fast disrupting (disintegration) of acylcontaining substrates (including organophosphorus compounds) is based on the use of highly reactive compounds. Reagents (catalysts) ability to provide “turnover” is of great impotence. Kinetic regularities for 4- nitrophenylacetate (PNPA) deacylation with 1-methyl-3-(2-hydroximinoethyl)-imidazolium chloride (oxime), chloral, and their mixtures were studied in water and cetyltrimethylammonium bromide (CTAB) solutions, under pH = const and [CTAB] = 10-2 M. Rate constants dependences upon nucleophile (catalyst) and detergent concentration are typical for reactions in water and micellar pseudophase. Transferring of PNPA deacylation from water into surfactant micelles leads to three orders rate enhancement. Kinetic experiments at different substrate concentrations indicate that a) first order rate constant in the chloral-CTAB system does not change up to tenfold excess of PNPA; b) first order rate constant in the oxime-CTAB system decreases for approx. 40% at PNPA excess; c) all advantages of “turnover” are achievable in the system chloral-oximeCTAB, where chloral provides first disintegration of acylated oxime with generation of highly reactive oximate-ion. Results obtained pave the way to modifying organized microheterogeneous systems, first of all, by surfactant structure changes.