S. B. Fedorov

The effect of electrolytes on the reaction rates and acid-base equilibria in ionic micelles

The influence of a number of electrolytes on the micellar effect of cetyltrimethylammoniurn bromide (CTAB) in the hydrolysis ofp-nitrophenyl acetate (1) and bis(p-nitrophenyl) methylphosphonate (2) and in the course of the acid-base dissociation of thep-nitroanilide of bis(chloromethyl)phosphinic acid (3) has been examined. The activity of the salts studied increases in the following order: MeCOOK<K2CO3<KCl<KBr<KNO3<p-MeC6H4SO3K. It has been found that in the presence of electrolytes the catalytic effect of CTAB micelles in the hydrolysis reactions of esters1 and2 decreases, and the pKa value of anilide3 increases. The results obtained are interpreted in terms of the pseudophase model of micellar catalysis. The analysis of the experimental data carried out using logarithmic coordinates revealed a relationship between phase transitions in micellar catalysis and in micellization.

Nucleophilic substitution in bis(4-nitrophenyl) ethyl phosphate in alkaline micellar solutions of 2-hydroxyethyldimethyloctadecylammonium bromide

A study was carried out on the mechanism of nucleophilic substitution in bis(4-nitrophenyl) ethyl phosphate (BNEP) in alkaline solutions of 2-hydroxyethyldimethyl-octadecylammonium bromide. In the presence of a 2-hydroxyethyl surfactant (Sur), nucleophilic properties of the 2-hydroxyethyl group, which is dissociated in alkaline media, are evident in addition to alkaline hydrolysis of the substrate. The second pathway arises beginning in the region of premicellar surfactant aggregates and is predominant in micellar solutions.

Catalysis of p-nitrophenyl butyl chloromethylphosphonate hydrolysis by higher amines

Conclusions1.Solutions of partly protonated higher primary amines (≥C6) contain mixed micelles that catalyze the hydrolysis of the ester bonds at the phosphorus through the general basic mechanism. The catalytic rate constants in the micellar phase are only very slightly dependent on the length of the hydrocarbon chain in the amine.2.At low concentrations, the higher amines form premicellar associates, for which the catalytic activity increases with increasing length of the radical.

Catalysis of the hydrolysis of esters of phosphorus acids byn-decylammonium chloride /n-decylamine mixed micelles

The effect ofn-decylammonium chloride/n-decylamine mixed micelles on the rate of hydrolysis of aryl esters of acids of four-coordinate phosphorus was studied spectrophotometrically. The shape of the concentration curves is characteristic of the micellar catalysis reactions. The binding constants of the substrate, critical micelle concentrations, and the rate constants in the micellar phase were determined. A specific effect of the structure of substrates on these parameters was shown.

Mechanism of nucleophilic substitution in O,O-dimethyl-O-(4-nitrophenyl)thiophosphate in micellar solutions of 2-hydroxyethyldimethyloctadecylammonium bromide

The mechanism of nucleophilic substitution in O,O-dimethyl-O-(4-nitrophenyl)-thiophosphate (DNTP) has been studied in alkaline micellar solutions of cationic 2-hydroxyethyl surfactant which displays nucleophilic properties on account of dissociation of the 2-hydroxyethyl group. Further transformation of the intermediate product formed can take place by regeneration of the initial nucleophilic form of the surfactant, or by formation of a new zwitterion form of phosphorylated surfactant.

Hydrolysis of bis(chloromethyl)phosphonic acid p-nitroanilide in aqueous micellar surfactant solutions

The hydrolysis of bis(chloromethyl)phosphonic acid p-nitroanilide has been studied in the pH range 6.86–13.0 and the effects of ionic surfactant micelles on this process have also been examined. The nature of the micellar effects of cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfate (SDS) on this reaction lead us to conclude that both the neutral and anionic forms of the substrate are reactive, and that in the range of pH > pKa hydrolysis of the ionic form of the anilide predominates, while at pH < pKa the reaction of the neutral form is predominant. The binding constants for both the neutral and anionic forms of bis(chloromethyl)phosphonic acid p-nitroanilide in micellar CTAB and SDS solutions have been determined using a kinetic method, as well as by measuring the changes in the acid-base properties of the substrate resulting from the influence of micelles.

Acid-base properties of bis(chloromethyl)phosphinic acid para-nitroanilide in aqueous micellar solutions of surface active agents

Micelles of the cation-active surface active agent (SAA), cetyltrimethylammonium bromide, decrease the pKa of bis(chloromethyl)phosphinic acid pnitroanilide in aqueous solutions by two units, while micelles of the anionactive SAA, sodium dodecyl sulfate increase the pKa of the same compound by 1.75 units. The presence of electrolytes in the solution lowers the influence of micelles on the acid-base properties of the anilide.

Kinetics of reaction of phosphorus acid esters with alcoholates in the presence of crown ether

Conclusions1.The reactivity of free anions and ionic pairs of alcoholates was studied in reactions with phosphorus acid esters in alcoholic solutions.2.Addition of 18-crown-6 to the reaction mixture causes acceleration of the reactions of esters having a thiophosphoryl group and slowing down of the reaction with esters having a P=0 group.3.The rate constants of the reactions with the participation of ions and ionic pairs increase on transition from lower to higher alcohols. The difference between the reactivity of the ionic pairs and that of the free anions of the alcoholates increases in the same direction also.

Alkaline hydrolysis of Etafos in micellar solutions of organophosphorus surfactants

Conclusions1.The effect of O-ethyl-N-alkylaminomethylphosphonic acid and monododecylphosphoric acid sodium salts on the kinetics of alkaline hydrolysis of Etafos was studied. Slowing of the reaction of alkaline hydrolysis is due to the formation of micelles of anion-active organophosphorus SF in solution.2.The dependence of the inhibiting effect of the micelles on the structure of the SF and concentration of the reagents and electrolytes in the solution was established.

Effect of the medium on the phosphorylation of monoethanolamine

Conclusions1.The rate constants and product ratios of N- and O-phosphorylation of monoethanolamine by p-nitrophenyl phenyl chloromethylphosphonate in different solvents were determined.2.In dipolar aprotic solvents phosphorylation of both reaction centers of monoethanolamine occurred to a commensurate degree, while in weakly polar solvents phosphorylation at oxygen predominated.