R. A. Shagidullina

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.

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.

The reactivity of phosphonic esters in aqueous micellar solutions of cationic surfactants

The micellar effect of cationic surfactants in alkaline hydrolysis of O-alkyl-O-aryl-chloromethyl phosphonates involves a positive contribution of concentrating the reagents and a negative effect of the micellar environment due to a loss in the activation entropy. The reactivity of substrates in micelles depends on both electronic and hydrophobic characteristics of substituents in the aryl group.

The effects of cetylpyridinium bromide micelles on the kinetics of alkaline hydrolysis of alkylp-nitrophenyl chloromethylphosphonate

Study of the kinetics of alkaline hydrolysis of alkylp-nitrophenyl chloromethylphosphonates in micellar solutions of cetylpyridinium bromide showed that the observed rate constant depends on the hydrophobicity of the substrates. A minor increase in the length of the alkyl chain in the substituent increases the catalytic effect in the series Et<Bu<C6H13. Further increase in the substrate hydrophobicity results in a decrease in the bimolecular rate constant in the micellar phase.

Aminolysis ofO-alkylO-4-nitropyenyl chloromethylphosphonates in reverse micellar solutions of the nonionic surfactant

The reaction ofn-hexylamine withO-alkylO-4-nitrophenyl chloromethylphosphonates in toluene solutions of poly(ethylene glycol)-600 monolaurate (PM) has been studied by spectrophotometry. The reverse micelles of the nonionic surfactant increase more than tenfold the observed rate constant of aminolysis. The catalytic activity of the surfactant is practically independent of the alkyl radical length of phosphonate. An increase in the concentration of amine results in a decrease in the catalytic efficiency. The character of the dependence of the rate constant on the concentration of PM is affected by the alkyl chain length of the substrate.

Alkylation reaction of amines by dimethyl phosphite

The alkylation reaction kinetics of a series of amines of different structures by dimethyl phosphite have been studied. Two-parameter correlation equations have been deduced, relating reactivity to steric and inductive effects of substituent s attached to the nitrogen atom in the amine; a Swain-Scott equation has also been deduced, establishing a correlation between the rate of alkylation and the nucleophilicity of the reaction site. When steric conditions at the nitrogen atom are fixed, as in the case of orthoaminomethylphenols, the reactivity follows a Brönsted equation.

Cetylpyridinium bromide-catalyzed reaction of ortho-aminomethylphenols with para-nitrophenyldiphenyl phosphate

Cetylpyridinium bromide micelles accelerate the reaction of paranitrophenyldiphenyl phosphate with orthoaminomethylphenol by more than an order of magnitude in aqueous micellar solutions. The rate constants for this reaction are, however, about 50 times lower in the micellar phase than in water, i.e., the principal factor responsible for micellar catalysis in this reaction is concentration of the reagent.

The micellar effect of the sodium bis(2-ethylhexyl)sulfosuccinate—decane—water reverse system on the hydrolysis of phosphonic acid esters

The reactivity of alkyl aryl chloromethylphosphonates in alkaline hydrolysis in the sodium bis(2-ethylhexyl)sulfosuccinate—decane—water reverse micellar system is mainly determined by the electronic properties of substituents and depends only slightly on their hydrophobicity.

The influence of the structure of tetracoordinate phosphorus acid esters on the catalytic effect of the sodium dodecyl sulfate-hexanol-water ternary reverse micellar system

The catalytic effect of the sodium dodecyl sulfate-hexanol-water ternary reverse micellar system in the alkaline hydrolysis ofO-alkylO′-aryl chloromethylphosphonates as a function of the substrate structure was studied. The micellar effect is mainly determined by a change in the electronic properties of the substituents, while the hydrophobicity plays a secondary role. The kinetic data were examined in the framework of the pseudo-phase model of micellar catalysis. The rate constants of the reaction in the surface layer and the partition constants of the reactants were calculated.

The inverted micellar catalysis of the reaction of 2-aminomethylphenols with 4-nitrophenyl bis(chloromethyl)phosphinate

The parameters of the reaction ofpara-substituted 2-aminomethylphenols with 4-nitrophenyl bis(chloromethyl)phosphinate in toluene catalyzed by reversed micelles of polyethylene glycol-600 monolaurate depend on the nucleophile structure. The efficiency of the catalytic action increases in the series of substitutes C9H19i<H<Cl. An increase in the catalytic activity of micelles in the region of structural rearrangement of micelle aggregates was observed.