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. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1366–1370., August, 2000.     

Catalytic effect of supramolecular system based on cationic surfactant and monopodands in nucleophilic substitution of phosphorus esters

The data are presented on the synthesis of podands with terminal quinoxaline fragments of rings and their influence on both the micellization properties of cetyltrimethylammonium bromide in a water—DMF solution and kinetics of basic hydrolysis of O-p-nitrophenyl O-ethyl chloromethylphosphonate and O-p-nitrophenyl O-hexyl chloromethylphosphonate in the absence and presence of surfactants. The mechanism of the podand effect on the reaction rate depends on the structures of phosphonate and podand. 1,8-Bis(3-ethyl-1,2-dihydro-2-oxoquinoxalin-1-yl)-3,6-dioxaoctane inhibits the basic hydrolysis of the substrates to 3—4 times. In a micellar solution of the surfactant, an approximately 20-fold acceleration of the reaction rate constant is observed. The observed rate constant decreases when podand is added to a micellar solution. The catalytic effect of the polycomponent system is due to concentrating of the reactants. The micellar microenvironment can exert both positive and negative effects on the reactivity of phosphonates.     

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. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1499–1504, August, 1998.     

Conformational Analysis of 1,2‐Di‐O‐Octanoyl‐Ethylene‐Glycerol During Aggregation

Conformational analysis of 1,2‐di‐O‐octanoyl‐ethylene‐glycerol during aggregation by 600 MHz ¹H NMR is described. In monomeric states, 1,2‐di‐O‐octanoyl‐ethylene‐glycerol exists in 75% anti‐conformer and 25% gauche‐conformer. The first critical micelle concentration of 1,2‐di‐O‐octanoyl‐ethylene‐glycerol is calculated to be 4.5 mM. In micellar states, 1,2‐di‐O‐octanoyl‐ethylene‐glycerol exists in 25% anti‐conformer and 75%) gauche‐conformer. When the concentration is greater than 10 mM, 1,2‐di‐O‐octanoyl‐ethylene‐glycerol probably aggregates to become the larger micelle, micelle II. In the second micellar state, 1,2‐di‐O‐octanoylethylene‐glycerol only exists in gauche‐conformer.     

Study of the reaction Fe(CN)4(bpy)2− + S2O82− in Sulfobetaine Aqueous Micellar Solutions

The reaction Fe(CN)₄(bpy)^2? + S₂O₈^2? has been studied in aqueous micellar solutions of N‐tetradecyl‐N,N‐dimethyl‐3‐ammonio‐1‐propanesulfonate, SB3‐14. The influence of changes in the surfactant concentration as well as in the peroxodisulfate ions concentration on k_obs was investigated. Spectroscopic and conductivity measurements have given information about the distribution of both anionic reagents between the aqueous and micellar pseudophases of the SB3‐14 micellar solutions. A discussion about the adequacy of various equations based on the pseudophase model to rationalize kinetic micellar effects for anion‐anion reactions in sulfobetaine micellar solutions has been done. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 225–231, 2001     

Supramolecular catalytic systems based on 1, 4-diazabicyclo[2.2.2]octane,its alkylated quaternary derivatives,and lanthanum nitrate

Spectrophotometry was used to study the catalytic effects of the systems composed of N-monoand N, N-dialkylated 1, 4-diazabicyclo[2.2.2]octanes and lanthanum nitrate on the hydrolysis rate of O-alkyl O-4-nitrophenyl chloromethylphosphonates (Alk = Et, Buⁿ, and n-hexyl). The mechanism of action and efficiency of the catalytic system depend on the structure of the heterocycle, its propensity to aggregation and complexation with the lanthanum cation, and the relative content of the components in solution. The maximum catalytic effect (a ～115-fold increase in the hydrolysis rate constant) was achieved in micellar solutions of the cationic monoalkylated derivative of 1, 4-diazabicyclo[2.2.2]octane and lanthanum nitrate.

     

Selectivity Control in Micellar Electrokinetic Chromatography by Modification of Micellar Surface with Cyclohexanol

Abstract

The effect of cyclohexanol added to the micellar solution of sodium dodecyl sulfate in the micellar electrokinetic chromatography of several aromatic compounds was investigated. Cyclohexanol (0.05–-0.10 M) diminished the capacity factors (k') of the solutes possessing hydrophilic functional groups which were solubilized near the micellar surface, whereas little changed the k' of the hydrophobic solutes solubilized in the micellar core. This selective effect was ascribed to the saturation of the micellar surface with cyclohexanol.     

Kinetics and mechanism of the homogeneous reaction between some manganese(III)-Schiff base complexes and hydrogen peroxide in aqueous and sodium dodecyl sulphate solutions

Summary The kinetics of the reaction between H₂O₂ and some Schiff base complexes of Mn^III have been investigated in both aqueous and micellar sodium dodecyl sulphate (SDS) solution. The reaction rate is first order in both H₂O₂ and [complex], and inversely proportional to [H⁺]. The second-order rate constant increases in the sequence [Mn(salophen)(OAc)] > [Mn(salen)(OH₂)]-ClO₄ > [Mn(salen)(OAc)]H₂O, where salen = N,N-bis-(salicylidene)ethylenediamine and salophen = N,N-bis-(salicylidene)-o-phenylenediamine. At SDS concentrations below the critical micellar concentration, there is almost no effect on the rate of reaction whereas at higher concentrations the reaction rate increases slightly. A mechanism involving Mn^II and a peroxo intermediate is proposed.     

Hydrolysis of phosphorus acid esters in the sodium bis(2-ethylhexyl)sulfosuccinate—<Emphasis Type="Italic">n</Emphasis>-nonane—polyethylene glycol—water supramolecular system before and after the percolation threshold

The kinetics of alkaline hydrolysis of O-ethyl O-p-nitrophenyl chloromethylphosphonate in a sodium bis(2-ethylhexyl)sulfosuccinate—n-nonane—polyethylene glycol—water reverse micellar system was studied in a wide range of concentrations of the surfactant and water. The sign of the catalytic effect of micelles is inverted in the presence of the polymer. A sharp change in the apparent rate constant of hydrolysis of the phosphonate was found in a region of the temperature percolation threshold. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 60–67, January, 2007.     

The α‐effect in micelles: Nucleophilic substitution reaction of p‐nitrophenyl acetate with N‐phenylbenzohydroxamate ion

Pseudo‐first‐order rate constants have been determined for the nucleophilic substitution reactions of p‐nitrophenyl acetate with p‐chlorophenoxide (4‐ClC₆H₄O^?) and N‐phenylbenzohydroxamate (C₆H₅CON(C₆H₅)O^?) ions in phosphate buffer (pH 7.7) at 27°C. The effect of cationic, (CTAB, TTAB, DTAB), anionic (SDS), and nonionic (Brij‐35) surfactants has been studied. The k_obs value increases upon addition of CTAB and TTAB. The effect of DTAB and other surfactants on the reaction is not very significant. The micellar catalysis and α‐effect shown by hydroxamate ion have been explained. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 26–31, 2006     

Nucleotide Coupling in Reverse Micelles

Nucleotide coupling was investigated in reverse micelles formed by (cetyl)trimethylammonium bromide (CTAB), in hexane/pentan-1-o1. In particular, the coupling of 2′ -deoxy-5′-O-methylcytidine 3′ O-phosphate, prepared by phosphoramidite chemistry, with 5′-amino-5-deoxythymidine was studied in the presence of a H₂O-soluble carbodiimide at (w_o) = 11 and 22 (w_o=[H₂O]/[CTAB]). The effect of w_o on the reaction rate was investigated. A solid-phase strategy was developed for the synthesis of 2′-deoxy-5′O-methyl-cytidyl-(3′-5′)-5′-amino-5′deoxythymidine. The nucleotide coupling yieldig the expected product occurred readily in reverse micelles. Nucleotide coupling is thus possible in reverse micelles, and this is discussed in connection with the micellar self-replication program.     

The salt effect in the alkaline hydrolysis ofO-ethylO-(p-nitrophenyl) chloromethylphosphonate catalyzed by cetylpyridinium bromide

The alkaline hydrolysis ofO-ethylO-(p-nitrophenyl) chloromethylphosphonate catalyzed by the micelles of cetylpyridinium bromide is inhibited on addition of KCl, K Br, or sodium salicylate (NaSal). This is caused by both a decrease in the nucleophile concentration in micelles owing to a reduction in the surface potential and a change in the micellar structure and properties. Dedicated to the memory of Academician M. I. Kabachnik in connection with his 90th anniversary. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1922–1926, October, 1998.     

Kinetic Studies on of Veratryl the Lignin Peroxidase Catalyzed Oxidation Alcohol by H2O2 in AOT/Isooctane/ Toluene/Water Reverse Micelles

The steady state kinetics of the lignin peroxidase （LIP） catalyzed oxidation of veratryl alcohol （VA） by H2O2 in a sodium bis（2-ethylhexyl） sulfosuccinate （AOT）/isooctane/toluene/water reverse micellar medium was studied and a comparison with the corresponding aqueous medium was made to understand the effect of the reverse micellar medium on the catalytic mechanism and kinetic parameters. Results indicated that the model reaction in the AOT reverse micelle followed the ping-pong mechanism with true kcat, Km,VA and KmH2O2 being 59.6min^-1, 13.9 mmol· L^-1 and 94.8 μmol·L^-1, respectively; inhibition of high level of H2O2 on LiP followed the reversible competitive pattern with Ki being 0.140 mmol·L^-1. The reaction mechanism and inhibition pattern in the AOT reverse micellar medium were the same as those in bulk aqueous medium, but the kinetic parameters except KmH2O2 were greatly different in the two media. The kcat and Ki values in the reverse micelle were approximately 2 and 20 times smaller than the corresponding values in the aqueous solution, but the Michaelis constant of VA was approximately 100 times greater than that in the aqueous solution. The above mentioned differences in the kinetic parameters were caused by the microheterogeneity and the interface of the AOT reverse micelle, which resulted in the partitioning of VA and H2O2, and by the changes of the conformation of LiP and the reactivity of the substrates.     

Solute partition study in aqueous sodium dodecyl sulfate micellar solutions for some organic reagents and metal chelates

The partition constants (K _d) have been estimated for nitrophenols, thiazolylazo dyestuffs and metal chelate compounds into the sodium dodecyl sulfate (SDS) micellar phase at an ionic strength of 0.10M [(H⁺, Na⁺)Cl^–] and at 20 °C. The equilibrium partition data obtained by batch-wise solution spectrophotometry (equilibrium shift method) agree well with those by the micellar electrokinetic capillary chromatography (MECC) with the SDS micellar pseudo-stationary phase. The MECC clearly discriminates a very small difference (0.03) in the logK _d values of some metal chelates. The plot of theK _d values with the van der Waals volume of the solute molecules obviously shows the leveling-off of theK _d values over solute size near 110 ml/mol, which seems to be consistent with the results obtained in the Triton X-100 micellar system. This phenomenon arises most probably from the rigidity of the micellar pseudo-phase (a micellar volume-constraint effect) in sharp contrast with true two-phase partitioning such as solvent extraction systems.     

Kinetics and mechanism of hydrogen peroxide oxidation of chromone-3-carboxaldehydes in aqueous acid and micellar media

Oxidation of chromone-3-carboxaldehyde (CCA) and substituted analogues by H₂O₂ has been carried out in aqueous acid (HCl and H₂SO₄) and micellar media. Reaction kinetics indicated order in [CCA] as well as [H₂O₂] to be unity while it is a fraction (1 > n > O) in [acid]. Reaction rates were found to be faster in the solvents of low-dielectric constant (D). Added salt (KCl or (NH₄)₂SO₄) increased the rate of oxidation marginally. On the basis of observed linearity of Amis plot and marginal positive salt effect, protonated CCA (enol form of CCA, a cation) and H₂O₂ (neutral molecule) were considered as reactive species in the rate limiting step. Reaction rates were found to be enhanced significantly in anionic and nonionic micellar (sodium dodecylsulfate (SDS) and Triton X-100 (Tx), respectively) media. However, cationic micelles [cetyl trimethyl ammonium bromide (CTAB)] indicated marginal retardation effect. Effect of anionic and cationic micelles has been interpreted in terms of electrostatic interactions, while that of nonionic micelles in terms of hydrophobic interactions. Structure-reactivity correlations have been interpreted by Hammett's equation. Negative “ρ” (reaction constant) values indicated cationic transition state. © 1996 John Wiley & Sons, Inc.     

Effect of the Media on the Quantum Yield of Singlet Oxygen (O2(1Δg)) Production by 9H‐Fluoren‐9‐one: Microheterogeneous Systems

The quantum yield (Φ_Δ) of singlet oxygen (O₂(¹Δ_g) production by 9H‐fluoren‐9‐one (FLU) is very sensitive to the nature of the solvent (0.02 in a highly polar and protic solvent, such as MeOH, to 1.0 in apolar solvents). This high sensitivity has been used for probing the interaction of FLU with micellar media and microemulsions based on anionic (sodium dodecyl sulfate, SDS; bis‐(2‐ethylhexyl)sodium sulfosuccinate, AOT), cationic (cetyltrimethylammonium chloride, CTAC) and nonionic (Triton X‐100, TX) surfactants. Values of Φ_Δ of FLU vary in a wide range (0.05–1.0) in both microheterogeneous media and neat solvent, and provide information on the microenvironment of FLU, i.e., on its localization within organized media. In ionic and nonionic micellar media, as well as in four‐component microemulsions, FLU is, to various extents, exposed to solvation by the polar and protic components of the microheterogeneous systems (water and/or butan‐1‐ol) in the micellar interfacial region (Φ_Δ=0.05–0.30). In contrast, in AOT reverse micelles (consisting of AOT as surfactant, cyclohexane as hydrophobic component, and water), FLU is located in the hydrophobic continuous pseudophase, and is totally separated from the micellar water pools (Φ_Δ≈1.0).     

Micelle-forming,liquid-crystalline properties,and catalytic effect of the mixed cetyltrimethylammonium bromide—polyethylene glycol(∼9) monoalkanoate(∼14)—water micellar system

The formation of mixed micelles in the surfactant cetyltrimethylammonium bromide—polyethylene glycol(9) monoalkanoate(14) binary system was shown. The stable lyomesophase involving monomers of both surfactants forms in the region of high surfactant concentrations in the temperature interval from 25 to 96 °C. In the binary micellar system, the alkaline hydrolysis of O-ethyl-O-p-nitrophenyl chloromethyl phosphonate is accelerated up to 30-fold compared with the reaction in water in the absence of a surfactant. The efficiency of catalysis depends on the molar ratio between both surfactants. The sign of the catalytic effect changes at high surfactant concentrations.     

Kinetics of reaction of sodiump-octylphenolate withO-ethyl-O-p-nitrophenyl ethylphosphonate

In aqueous and aqueous-alkaline solutions, sodiump-octylphenolate forms anionic micelles that absorbO-ethyl-O-p-nitrophenyl ethylphosphonate before the reaction that proceeds on the micellar surface. The micelle formation is suppressed in systems containing organic solvent and water. However, for these systems, the rate of the reaction with phenolates is affected by the association of ions in the ion pairs.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 850–853, April, 1996.     

Effect of 1-butanol on the surface structure of ionic micelles and location of its solubilization site: Electron spin echo modulation study with x-doxylstearic acid spin probes

Electron spin echo modulation studies with a series of x-doxylstearic acids (x = 5, 7, 10, 12, and 16) have been carried out for sodium- and tetramethylammonium dodecylsulfate and dodecyltrimethylammonium chloride frozen micellar solutions containing protiated and perdeuterated 1-butanol. Modulation effects due to nitroxide interactions with deuterium in water and butanol have been measured versus doxyl group position. The effect of 1-butanol on the micellar surface and internal micellar structure has been evaluated and the average location of 1-butanol in these micelles has been deduced to be in the outer annulus of the micelle core.     

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.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2003–2006, August, 1996.