Design of green microorganized systems for decontamination of ecotoxicants

Abstract

Due to population upsurge, pesticides (derivatives of organophosphorus acids included) find widespread use in agriculture. The toxicity and long-term environmental hazard of such compounds require detailed studies on decomposition mechanisms of the pesticides and development of efficient, readily available, and inexpensive systems for their decontamination. A simple and straightforward method for the decomposition of organophosphorus compounds involves their reactions with nucleophiles. Studies on the reactivity of "normal" and α-nucleophiles toward electron-deficient centers allowed us to state a number of basic principles on the nature of the α-effect. One of the most important conclusions is: It is unlikely that the structure variations in the known α-nucleophiles will result in higher reactivity than that of hydroxylamine anion. As a practical matter, the essential disadvantages of decomposition of organophosphorus compounds in water and organic solvents are: (i) instability of active nucleophiles and oxidizing agents, (ii) corrosiveness, and (iii) extremely low solubility of organophosphorus compounds in water. These dictate the strategy of further studies, namely, carrying out the reaction in microorganized media. The first research line involves the development of the functional imidazole-based detergents functionalized with α-nucleophilic fragments. A number of efficient detergents were first synthesized. An examination of the nucleophilicity of the functional fragments in water and in the micellar phase and quantitative assessment of the factors responsible for the micellar effects showed unambiguously that the main cause of the observed accelerations is the substrate concentrating in the micellar pseudophase. The second research line consists of studies on the reactivity of versatile oxidative/nucleophilic systems involving H2O2/activator and polyhalide ion organocomplexes in water, aqueous alcohols, and micelles of cationic detergents. The novel sources of "active" halogen are highly competitive both with conventional hazardous chlorine derivatives and "green" systems involving H2O2/activator.

Role of the hydrophobic properties of functional detergents on micellar effects in the dissociation of environmental toxicants

“…Firstly, microheterogeneous systems derived from functional detergents serve, to some extent, as models for studying the action of hydrolytic enzymes, which provides for the investigation of various features of enzymatic catalysis in simpler systems. The increase in the reaction rate in micelles of functional surfactants in comparison with water may reach factors of 10 2 -10 7 , which makes such systems comparable in efficiency with enzyme systems [1,2]. The observed effects are largely a function of the role of the microenvironment of that part of the micelles, in which the chemical reaction proceeds and the hydrophobic binding of the substrate by the micelle core [1][2][3][4].…”

“…The increase in the reaction rate in micelles of functional surfactants in comparison with water may reach factors of 10 2 -10 7 , which makes such systems comparable in efficiency with enzyme systems [1,2]. The observed effects are largely a function of the role of the microenvironment of that part of the micelles, in which the chemical reaction proceeds and the hydrophobic binding of the substrate by the micelle core [1][2][3][4]. Secondly, the intensive study of the reactivity of functional detergents has had and still has marked applied significance related to the decomposition and utilization of environmental toxicants, in particular the highly toxic esters of organophosphorus acids [1,[5][6][7][8].…”

Catalysis of the alkaline hydrolysis of 4-nitrophenyl diethyl phosphonate by cationic dimeric surfactant micelles

“…These new surfactants have low critical micelle formation concentrations (<5·10 -5 mol/L) and Krafft temperatures (£0°C). Depending on the pH of the medium, the alkaline hydrolysis of 4-nitrophenyl diethyl phosphonate, which is a model of organophosphorus ecotoxicants, proceeds 20-80 times more rapidly in the presence of gemini surfactant micelles than in water.The enormous interest in recent decades concerning the preparation and study of dimeric (gemini) surfactants and derived organized molecular systems has been due to the unique physicochemical characteristics of these compounds [1, 2], primarily, their anomalously low critical micelle concentrations (CMC » 10 -5 -10 -6 mol/L), which are one or two orders of magnitude less than for the corresponding monomeric surfactants, more efficient lowering of the surface tension of aqueous solutions, better solubilization of compounds with low solubility in water, and micelle polymorphism [2].Gemini surfactants may be seen as a promising basis for organized molecular systems corresponding to the requirements of "green chemistry" for the detoxification and utilization of toxic phosphorus acid esters [3]. The decomposition of ecotoxicants should be carried out under mild conditions using inexpensive and nontoxic solvents.…”

Reactivity of micelle-forming 1-alkyl-3(1-oximinoethyl)pyridinium bromides in acyl group transfer reactions

“…Upon dissolution in water in amounts exceeding the critical micelle concentration, these compounds combine in supermolecular ensembles with a functionalized surface, on which the concentration of the reactive groups will be maximalized for such systems [1][2][3]. This feature of functional detergents permits anomalously high rates of acyl group transfer reactions, while systems derived from such detergents hold considerable promise as agents for the efficient cleavage of acyl substrates and, especially, of highly toxic esters of phosphoric and phosphonic acids [1,2].The micellar effects of such organized molecular systems depend on a host of factors but primarily on 1) the change in the properties of the medium upon transferring the reaction from water to the micellar pseudophase and 2) concentration of the substrate in the surfactant micelles [1-6]. The first factor may lead to change in both nucleophilicity and the acid-base properties of the functional group [4,5].…”

“…Upon dissolution in water in amounts exceeding the critical micelle concentration, these compounds combine in supermolecular ensembles with a functionalized surface, on which the concentration of the reactive groups will be maximalized for such systems [1][2][3]. This feature of functional detergents permits anomalously high rates of acyl group transfer reactions, while systems derived from such detergents hold considerable promise as agents for the efficient cleavage of acyl substrates and, especially, of highly toxic esters of phosphoric and phosphonic acids [1,2].…”