The effect of the nature of the head group on the micellar effects of functional/cationic co-micelles in acyl transfer reactions

Abstract

toluenesulfonic acids was investigated. It was shown that the nucleophilicity of the functional groups in the surfactant does not undergo substantial changes with variation in the nature of the head group of the cationic surfactant and the fraction of functional detergent in the co-micelle. This makes it possible to create systems that decompose organophosphorus substrates unusually quickly even with small contents of the functional surfactant. The use of organized molecular systems, including micelles and microemulsions based on surfactants (SFA) opens up wide possibilities for the control of reaction rates [1-3]. Most of the examples of the effect of micelles on the rate of chemical processes relate to the reactions of anionic nucleophiles with organic substrates in the presence of cationic micelles [2]. One of the important regions of application of the micellar effects of surfactants is the problem of the decomposition and utilization of ecotoxicant substrates of the organophosphorus type. It requires the search for and construction of effective systems characterized by high nucleophilicity and solubilizing power in relation to organophosphorus compounds (OPC) [3][4][5]. A promising method of modifying a surfactant involves the creation of functional SFAs by introducing functional groups with given properties into the head group [2,4]. As the basis of highly effective micellar systems in the decomposition of organophosphorus compounds we proposed [5-7] a new class of functional detergents, containing an imidazole ring and typical fragments of a-nucleophiles -oximate (I), hydroxamate (II), and amidoximate (III) groups.Earlier we had shown that the micelles of functional surfactants I-III and their co-micelles with cationic surfactantscetyltrimethylammonium chloride (CTAC) -decompose the 4-nitrophenyl esters of diethylphosphoric (NPDEP), 0040-5760/07/4301-0035

From α-nucleophiles to functionalized aggregates: exploring the reactivity of hydroxamate ion towards esterolytic reactions in micelles

“…Another highly efficient micellar systems for the decomposition of organophosphates were proposed by this team [62,55]. They investigated a new class of functional detergents, containing an imidazole ring and typical fragments of α-nucleophiles; oximate, hydroxamate 29, and amidoximate groups in mixed micelles with cationic surfactants to analyze both nucleophilicities of specific moieties and observed reaction rates and apparent pK a as a function of mole fraction of the functionalized surfactant in the mixed micelle.…”

REACTIVITY OF NUCLEOPHILES AND α-EFFECT IN SUBSTITUTION PROCESSES AT ELECTRON - DEFICIENCY CENTERS (Part 2)

“…The introduction of tetraalkylammonium [148; 149], imidazolium [151,[157][158][159][160] or pyridinium [151] positively charged center in hydroxamic acid leads to an increase in its solubility in water [151,148,158], and undoubtedly, reduces the constants of acid ionization of the hydroxamate fragment. An increase in the distance between a functional group and a charged center neutralizes influence of the latter [156].…”

“…The studies carried out cover compounds with a rather diverse structure [148,149,154,[157][158][159][160][161][162][163][164][165][166][167][168][169][170][171][172], and in papers [148,149,[161][162][163][164][165][166][167] much attention was paid to the study of the reactivity of surfactants, the head group of which is structurally similar to AChE pyridinium reactivators (2-PAM, 4-PAM, etc. [77-79]).…”

“…Varying the nature of the head group. The literature [148,149,154,[157][158][159][160][161][162][163][164][165][166][167][168][169][170][171][172] describes functional detergents containing imidazolium, pyridinium, tetraalkylammonium fragments and an oximate group in the head part of the molecule. The study of their reactivity in the processes of model substrates (NPA, DPP, NP-DPP, NPDEP, NPDEP, NPDETP, NPTS, NPB) cleavage showed that they are effective acceptors of acyl groups.…”

“…The study of their reactivity in the processes of model substrates (NPA, DPP, NP-DPP, NPDEP, NPDEP, NPDETP, NPTS, NPB) cleavage showed that they are effective acceptors of acyl groups. Unfortunately, it is rather difficult to carry out a full-fledged comparative analysis based on the available literature data [148,149,154,[157][158][159][160][161][162][163][164][165][166][167][168][169][170][171][172]. This is because the authors use substrates of different reactivity and hydrophobicity, and reaction conditions are significally different (surfactant concentration, degree of ionization of a functional fragment, degree of substrate binding, temper-ature, additives of co-detergents, organic solvents, etc.…”