V. E. Bel'skii

Interaction between primary aliphatic amines and carboxylic acid esters in aqueous micellar solutions of cationic surfactants

The effects of cetylpyridinium bromide (CPB) on the acid-base equilibria of primary aliphatic amines and on the kinetics of reactions of the amines withp-nitrophenyl acetate (PNPA) andp-nitrophenyl caprylate (PNPC) were studied by potentiometric titration and UV spectroscopy. The values of apparent pKa of the amines in the micellar phase, binding constants of their neutral forms, and the surface potentials of micelles were determined. Cetylpyridinium bromide accelerates the aminolysis of PNPA by factors of 3 to 8 by forming mixed micellar aggregates with the amines. The shift of pKa values of the amines in micellar solutions is not the only factor that enhances their reactivity. The substrate specificity was found: in contrast to the reaction with PNPA, CPB accelerates (by factors of 15 to 65) or retards (by factors of 4 to 6) the aminolysis of PNPA depending on the hydrophobicity of the nucleophilic reagent. The binding constants of substrates, the rate constants in the micellar phase, and the critical concentrations of micellization were determined from the data obtained.

Isokinetic relationships for nucleophilic substitution reactions at the saturated carbon atom. Reactions in aqueous solutions

An isokinetic relationship (IKR) with the parametersTiso=6145 K and logkiso=10.622 is valid for nucleophilic substitution reactions at the saturated carbon atom with the participation of anionic nucleophiles in aqueous solutions. The IKR describes the rate constants of the reactions with different anionic nucleophiles, leaving groups, and substituents at the electrophilic reaction center. Similar reactions with neutral nucleophiles, which follow another mechanism, are described by a separate IKR withTiso=−1232 K and logkiso=16.226. The reactions of haloforms with hydroxide ion, which proceed by a specific mechanism involving the haloform ionization equilibrium followed by α-elimination of the halide ion, are described by yet another IKR withTiso=−1463 K and logkiso=21.057.

Kinetics of alkaline hydrolysis of esters of phosphorus acids in micellar and hexagonal phases in the cetyldimethylethylammonium bromide—NaOH—water system

The influence of micellar (Mi) and hexagonal (E) mesophases of the cetyldimethylethylammonium bromide—NaOH—water system (I) on the rates on alkaline hydrolysis ofO-p-nitrophenyl-O,O-diethyl phosphate (2),O-p-nitrophenyl-O-ethylethyl phosphonate (3), andO,O-di(p-nitrophenyl)methyl phosphonate (4) was studied by UV spectrophotometry. The binding constants of the substrates, critical micelle concentrations, and rate constants of reactions in the micellar phase were determined. In micellar solutions of systemI, a tenfold increase in the rates of alkaline hydrolysis of2–4 was observed. An increase in the degree of medium ordering during the formation of the E-phase results in a twofold acceleration of alkaline hydrolysis of2 and3 and in the inhibition of this process in the case of4.

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.

Isokinetic relationships for nucleophilic substitution at the saturated carbon atom. Reactions with anions in the gas phase and various solvents

Isokinetic relationship (IKR) with the parameters Tiso = 6103 K and logkiso = 10.402 is applicable to the rate constants for 165 reactions of nucleophilic substitution at the saturated carbon atom involving anionic nucleophiles in proton-donor and polar aprotic solvents and their mixtures. For analogous reactions in the gas phase proceeding via a specific mechanism, IKR is obtained with the parameters Tiso = 1505 K and logkiso = 9.972, which is applicable to the reactions occurring under various pressures of an inert gas.

Basicity of o-aminomethylphenols in nonaqueous media

Summary1.The basicity of o-aminomethylphenols in nitromethane, acetonitrile, and ethanol is lower in comparison with benzylamines, which do not have any intramolecular hydrogen bonds.2.The influence of the intramolecular hydrogen bond on the basicity of the o-aminomethylphenols increases in the following series of solvents: ethanol<water<acetonitrile-nitromethane.3.Between the values of pKa of the o-aminomethylphenols and benzylamines in water, ethanol, nitromethane, or acetonitrile, linear correlations are obtained with slopes close to unity.4.The relationship between pKa in nitromethane and in acetonitrile is common for primary, secondary, and tertiary alkylamines, benzylamines, o-aminomethylphenols, anilines, and pyridine.

Kinetics of the reactions of p-nitrophenylbis(chloromethyl)phosphinate with primary and secondary amines

Study has been made of the kinetics of the reaction of p-nitrophenylbis(chloromethyl)-phosphinate with primary and secondary amines. Reaction proceeds through rupture of the ester bond at the P atom and is catalyzed by a second amine molecule. The reaction rate is determined by induction and steric effects in the amine substituents. The activation energy for the reaction with n-butylamine is negative.

THE INFLUENCE OF THE STRUCTURE OF ORGANIC COMPOUNDS ON THEIR SOLUBILIZATION BY SODIUM DODECYL SULFATE MICELLES

Regression analysis of the structural influence of organic compounds on the binding constants in aqueous micellar solutions of sodium dodecyl sulfate (SDS) was performed. Regression equations were obtained using empirical and calculated descriptors that characterize the mechanisms of interaction of substances with micelles and water. For alkanes, compounds with hydroxyl groups (alcohols, phenols, and benzoic acids), and aromatic and aliphatic hydrocarbons without OH groups, the binding constants were described by particular regression equations, which indicate the specificity of solubilization of these types of organic compounds by SDS micelles from aqueous solutions.

Catalysis of the hydrolysis of di(p-nitrophenyl) methylphosphonate by polyamines

ConclusionsThe kinetics of the hydrolysis of di(p-nitrophenyl)methylphosphonate in aqueous solutions of triethylenetetramine and tetraethylenepentamine have been studied at various pH values. The catalytic rate constants for the neutral and monoprotonated forms of the polyamines are represented by the Brønsted equation as with the primary aliphatic amines and for the diprotonated forms they are represented together with the secondary aliphatic amines.

Hydrolysis of substituted 2-ethoxy-2-oxo-1-oxa-2-phosphoindans

Conclusions1.We synthesized a number of 2-ethoxy-2-oxo-1-oxa-2-phosphoindans with substituants in the benzene ring and studied their reactivity in neutral aqueous hydrolysis.2.It was shown that the rate constant for the hydrolysis of the phosphoindans is highly sensitive to a change in their structure, which sensitivity is determined by the dual effect of the substituents on the reaction center.