L. A. Kudryavtseva

Catalysis of nucleophilic substitution reactions in supramolecular systems

The factors determining the catalytic effect of supramolecular systems on the nucleophilic substitution reactions are analyzed. The role of the structural and phase transitions of nanoaggregates in the catalytic mechanism are determined. The substrate specificity is shown for different structures of the supramolecular composition.

Role of surface potential in the catalytic action of micelles of cationic surfactants with a hydroxyalkyl fragment in the head group

The surface potential in aqueous micellar solutions of a series of cetyltrialkylammonium bromides containing a hydroxyalkyl fragment in the head group was determined with a spectral probe (p-nitrophenol). It was found that the catalytic effect exerted by these surfactants in solution on the base hydrolysis of carboxylic acid esters is determined by two factors. First, the charged nucleophile is concentrated at the micelle surface. Second, hydrogen bonding of the substrate with the hydroxyalkyl substituents results in its activation.

Geminal alkylammonium surfactants: Aggregation properties and catalytic activity

Geminal alkylammonium surfactants containing a hexamethylene spacer show a specific behavior, namely, a catalytic effect at low concentrations of the detergent in the system. The critical micellization concentrations of these surfactants are by an order of magnitude lower than those of the related surfactants with one hydrophobic fragment. The effect exerted on the hydrolysis of carboxylic acid esters by micellar structural rearrangements induced by addition of a supporting electrolyte is determined.

Catalytic Effect of Multicomponent Supramolecular Systems in Phosphoryl-Group Transfer Reactions

The catalytic effect of the cetyltrimethylammonium bromide–poly(ethylenimine)–water system in the hydrolysis reactions of phosphonic acid esters (an increase in the rate constant by three orders of magnitude) is due to the concentration of reactants in polymer–colloid complexes and changes in their microenvironments. The catalyst efficiency depends on the structures of substrates, surfactants, and polymers.

Reactivity of O-alkyl O-p-nitrophenyl chlorometylphosphonate in aqueous micellar solution of surfactants

Abstract The comparison of the reactivity of O-alkyl O-p-nitrophenyl chlorometylphosphonates in two processes - basic hydrolysis and the reaction with o-aminomethyl phenols (AMP) reveals that both in the absence of cetylpyridinium bromide (CPB) and in the CPB micelles nucleophilic activity of the hydroxide-ion is much higher (by 2 orders) than that of AMP. In the basic hydrolysis the concentration factor is found to play a more significant role in comparison with the reaction of the substrate with AMP due to the higher binding constants of the reagents. A variation in the substrate binding constant depending on the reaction medium and the reaction type was revealed.

Supramolecular catalytic systems based on calix[4]resorcinarene for nucleophilic substitution in phosphorous acid esters

The aggregation and catalytic effect in the reaction of hydrolytic decomposition of phosphorous acid esters are studied for series of systems such as calixarene (CA)-sodium dodecyl sulfate (SDS), CA-poly(ethylene imine) (PEI), SDS-PEI, and CA-SDS-PEI. Using dynamic light scattering, sizes of aggregates are determined, cloud point is estimated, and catalytic effect is studied. Data obtained are consistent with the assumption of the joint aggregation in systems studied. The possibility of the passage from 20-fold inhibiting effect to the catalysis (higher than the order of magnitude) of studied reaction by the immobilization of anionic nanoaggregates (nanoreactors) on a catalytically active polymer matrix is demonstrated. The possibility of the passage from microheterogeneous to heterogeneous system and the separation of catalyst from the products are established.

Phosphorylation of Polyethylene Imines in Chloroform in the Presence of Calix(4)resorcinarenes

Kinetics of the reaction of alkylated polyethylene imines with 4-nitrophenyl bis(chloromethyl)-phosphinate in chloroform in the absence and in the presence of substituted calix[4]resorcinarenes were studied by UV spectrophotometry. It was shown that calixarenes forming mixed aggregates with polyethylene imines have a catalytic effect on the polymer phosphorylation process. The catalytic effect depends on the structure of polyethylene imine and the component ratio in the system.

Micellization properties and the catalytic effect of the aqueous cetyltrimethylammonium bromide-Triton X-100 binary system in nucleophilic substitution in esters of phosphorus acids

The aggregation properties and catalytic effect of the cetyltrimethylammonium bromide-Triton X-100 binary system in nucleophilic substitution in esters of phosphorus acids are studied in the region of normal micelles and oil/water microemulsions. In the presence of phenol, the dissociation of O-alkyl-O-para-nitrophenyl chloromethyl phosphonates is up to 200 times more rapid than the same reaction in water. The efficiency of catalysis depends on the molar ratio of the surfactants and is determined by several factors: concentration, changes in the microenvironment of the reactants, and the shift of the pKa of phenol.

The factors determining the micellar effects on nucleophilic substitution reactions

Abstract Kinetic study of the reaction of p-nitrophenyl diphenyl phosphate with 2-aminomethylphenols and the basic hydrolysis of ethyl p-nitrophenyl ethyl phosphonate have shown that in direct micelles the concentration factors is mainly responsible for the acceleration of nucleophilic substitution reaction while the micellar microenvironment negatively affects the reactivity and results in a diminution in the micellar rate effect. The considerable contribution to the micellar catalysis is made by the acid-base equilibrium shift of reagents. On the contrary, in reverse aggregates the micellar microenvironment favours the reaction and mostly underlies the mechanism of the catalysis, while the concentration factors plays a minor role.

Aggregation behavior and catalytic properties of systems based on aminomethylated calix[4]resorcinarenes and poly(ethylene) imines

Self-assembling in systems poly(ethylene) imine-aminomethylated calix[4]resorcinarene-water-DMF (30 vol%) and catalytic properties of these compositions in hydrolysis of 4-nitrophenylbis (chloromethyl)phosphinate are studied. Critical concentrations of association, aggregates radii, and kinetic parameters of the reaction are established.