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Structure of the head group, nucleophilicity, and micellar effects of functional detergents in acyl transfer reactions

“…The kinetic relationships for the decomposition of the substrates by the micelles of the surfactant I are similar to those established earlier for III and IV [7][8][9]. The increase of the observed reaction rate constant with increase of pH indicates that, as also in water, the oximate ion acts as nucleophilic reagent (Fig.…”

“…Such a bonding constant is typical of very hydrophobic substances and of 4-nitrophenyl diphenyl phosphate in particular [3]. For NPDEP the value of K S hardly exceeds~5·10 2 L/mol [7][8][9], and the fraction of bonded substrate a S £ 0.2 (with C 0 = 4·10 -4 M). It is therefore quite difficult to explain the decrease of the rate with C 0 ³ 4·10 -4 M. In connection with the foregoing we undertook a detailed kinetic investigation of the decomposition of NPDEP, NPDEPS, and NPTS in co-micelles in the presence of II and the co-detergent cetyltrimethylammonium bromide (CTAB).…”

“…Therefore, during study of the micellar effects of such detergents, as during their use in systems for the decomposition of excotoxicants, it is necessary to introduce an inert surfactant -a co-detergent, and this makes the system multicomponent and less attractive from the practical standpoint. The nucleophilicity of functional detergents can be predicted on the basis of the reactivity of analogs not forming micelles [1,2,[7][8][9][10]. This opens up the possibility of specific modification of the structure of the surfactant with the aim of producing compounds with the required level of nucleophilicity.…”

“…This opens up the possibility of specific modification of the structure of the surfactant with the aim of producing compounds with the required level of nucleophilicity. This is the approach that we used during the creation of functional detergents based on imidazole [7][8][9]. With variation of the position of the oximate group in the series of hydroxyiminomethyl-1-cetylpyridinium halides the variation of the observed rates of decomposition of 4-nitrophenyl diethyl phosphate corresponds likewise to the variation of the basicity of the a-nucleophilic fragment in hydroxyimino-1-methylpyridinium halides [1].…”

“…e The k 2 m /V m value was calculated from the pH dependence. f During calculation of k 2 m /V m the bonding constants were taken from [7][8][9]. g Determined from the limiting values of k ob , s -1 .…”