Micellar Catalyzed Reactions Research Articles

Micellar catalysis beyond the hydrophobic effect: Efficient palladium catalyzed Suzuki-Miyaura coupling of water and organic solvent insoluble pigments with food grade surfactants

Micellar catalysis is having a dramatic impact in improving the sustainability of a wide variety of chemical transformations, including most of the popular palladium mediated carbon–carbon and carbon–nitrogen bond forming reactions. The Suzuki-Miyaura coupling is one of the earliest examples of micellar catalyzed reactions and it is still a very much active research field even at industrial scale. So far, micellar catalysis proved particularly efficient in enabling the high yield, low catalyst loading and mild reaction condition coupling of hydrophobic reagents in a water solution of selected surfactants. In this paper we show that the use of aqueous solutions of a mixture of food grade lecithin and the industrial surfactant Tween 80 not only enables efficient coupling in water of hydrophobic chemicals, but also provides a very resourceful tool for the functionalization of water and organic solvent insoluble pigments of interest for the dye and printed electronic industries.

Cationic micellar structural growth and their viscoelastic behaviour in mixed surfactants system

ABSTRACT This study discusses the mechanistic details of the cationic micellar transition (growth) in a mixed surfactant system. The aqueous mixed surfactant solution contains cationic micelles at a concentration greater than CMC (critical micelle concentration). These micelles yield a pseudophase of various viscoelastic behaviours. Effects of inert counterionic salts (MX) on the rates of bimolecular reactions (with one of the reactants as reactive counterion) in the presence of ionic micelles may result in either positive or negative catalysis. The kinetics of mixed cationic-noionic micellar-catalysed bimolecular reactions has been used as a probe in the report.

Micellar Effect On Dephosphorylation Of Bis-4-Chloro-3,5- Dimethylphenylphosphate Ester By Peroxy Anions

The rate enhancement depends on the hydrophobicity of the nucleophile. The micellar catalyzed reaction between bis-4-chloro-3,5-dimethylphenylphosphate ester and hydroxide or hydroperoxide anions has been examined in buffered medium (pH 8-10). First order rate constant (Kψ) for the reaction of hydroxide ion with bis-4-CDMPP go through maxima with the increasing concentration of cetyltrimethylammoniumbromide (CTABr). Micelles of CTABr very effective catalyst to the reactions of phosphate diesters. Rate constants measured with OH2 - ions are approximately twice and thrice than that of OH - ions in presence of CTABr.

CTABr 미셀 용액속에서 2-Alkylbenzimidazole 음이온에 의해 추진되는 Isopropyl phenyl-4-nitrophenyl phosphinate(IPNPIN)의 탈인산화반응

This study is mainly focused on micellar effect of cetyltrimethyl ammonium bromide(CTABr) solution including alkylbenzimidazole(R-BI) on dephosphorylation of isopropyl-4-nitrophenylphosphinate(IPNPIN) in carbonate buffer(pH 10.7). The reactions of IPNPIN with R-<TEX>$BI^{\ominus}$</TEX> are strongly catalyzed by the micelles of CTABr. Dephosphorylation of IPNPIN is accelerated by <TEX>$BI^{\ominus}$</TEX> ion in <TEX>$10^{-2}$</TEX> M carbonate buffer(pH 10.7) of <TEX>$4{\times}10^{-3}$</TEX> M CTABr solution up to 89 times as compared with the reaction in carbonate buffer by no benzimidazole(BI) solution of <TEX>$4{\times}10^{-3}$</TEX> M CTABr. The value of pseudo first order rate constant(<TEX>$k_{\Psi}$</TEX>) of the reaction in CTABr solution reached a maximum rate constant increasing micelle concentration. Such rate maxima are typical of micellar catalyzed bimolecular reactions. The reaction mediated by R-<TEX>$BI^{\ominus}$</TEX> in micellar solutions are obviously slower than those by <TEX>$BI^{\ominus}$</TEX>, and the reaction rate were decreased with increase of lengths of alkyl groups. It seems due to steric effect of alkyl groups of R-<TEX>$BI^{\ominus}$</TEX> in Stern layer of micellar solution. The surfactant reagent, CTABr, strongly catalyzes the reaction of IPNPIN with R-BI and its anion(R-<TEX>$BI^{\ominus}$</TEX>) in carbonate buffer(pH 10.7). For example, <TEX>$4{\times}10^{-3}$</TEX> M CTABr in <TEX>$1{\times}10^{-4}$</TEX> M BI solution increase the rate constant(<TEX>$k_{\Psi}=98.5{\times}10^{-3}\;sec^{-1}$</TEX>) of the dephosphorylation by a factor ca.25, when compared with reaction(<TEX>$k_{\Psi}=3.9{\times}10^{-4}\;sec^{-1}$</TEX>) in <TEX>$1{\times}10^{-4}$</TEX> M BI solution(without CTABr). And no CTABr solution, in <TEX>$1{\times}10^{-4}$</TEX> M BI solution increase the rate constant(<TEX>$k_{\Psi}=3.9{\times}10^{-4}\;sec^{-1}$</TEX>) of the dephosphorylation by a factor ca.39, when compared with reaction (<TEX>$k_{\Psi}=1.0{\times}10^{-5}\;sec^{-1}$</TEX>) in water solution(without BI). This predicts that the reactivities of R-<TEX>$BI^{\ominus}$</TEX> in the micellar pseudophase are much smaller than that of <TEX>$BI^{\ominus}$</TEX>. Due to the hydrophobicity and steric effect of alkyl group substituents, these groups would penetrate into the core of the micelle for stabilization by van der Waals interaction with long alkyl groups of CTABr.

Validated spectrophotometric methods for determination of Alendronate sodium in tablets through nucleophilic aromatic substitution reactions

BackgroundAlendronate (ALD) is a member of the bisphosphonate family which is used for the treatment of osteoporosis, bone metastasis, Paget's disease, hypocalcaemia associated with malignancy and other conditions that feature bone fragility. ALD is a non-chromophoric compound so its determination by conventional spectrophotometric methods is not possible. So two derivatization reactions were proposed for determination of ALD through the reaction with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) and 2,4-dinitrofluorobenzene (DNFB) as chromogenic derivatizing reagents.ResultsThree simple and sensitive spectrophotometric methods are described for the determination of ALD. Method I is based on the reaction of ALD with NBD-Cl. Method II involved heat-catalyzed derivatization of ALD with DNFB, while, Method III is based on micellar-catalyzed reaction of the studied drug with DNFB at room temperature. The reactions products were measured at 472, 378 and 374 nm, for methods I, II and III, respectively. Beer's law was obeyed over the concentration ranges of 1.0-20.0, 4.0-40.0 and 1.5-30.0 μg/mL with lower limits of detection of 0.09, 1.06 and 0.06 μg/mL for Methods I, II and III, respectively. The proposed methods were applied for quantitation of the studied drug in its pure form with mean percentage recoveries of 100.47 ± 1.12, 100.17 ± 1.21 and 99.23 ± 1.26 for Methods I, II and III, respectively. Moreover the proposed methods were successfully applied for determination of ALD in different tablets. Proposals of the reactions pathways have been postulated.ConclusionThe proposed spectrophotometric methods provided sensitive, specific and inexpensive analytical procedures for determination of the non-chromophoric drug alendronate either per se or in its tablet dosage forms without interference from common excipients.Graphical abstract

Diphenyl-4-nitrophenylphosphinate(DPNPIN)의 탈인산화반응에 미치는 Alkylbenzimidazole의 친핵적 및 Cetylpyridinium chloride(CPyCl) 미셀 촉매효과

Abstract This study is mainly focused on micellar effect of cetylpyridinium chloride(CPyCl) solution including alkyl- benzimidazole(R-BI) on dephosphorylation of diphenyl-4-nitrophenylphosphinate(DPNPIN) in carbonate buffer(pH 10.7). The reactions of DPNPIN with R-BI ⊖ are strongly catalyzed by the micelles of CPyCl. Dephosphorylation of DPNPIN is accelerated by BI ⊖ ion in 10 -2 M carbonate buffer(pH 10.7) of 4×10 -3 M CPyCl solution up to 100 times as compared with the reaction in carbonate buffer by no BI solution of 4×10 -3 M CPyCl. The value of pseudo first order rate constant(k mBI ) of the reaction in CPyCl solution reached a maximum rate constant increasing micelle concentration. Such rate maxima are typical of micellar catalyzed bimolecular reactions. The reaction mediated by R-BI ⊖ in micellar solutions are obviously slower than those by BI ⊖ , and the reaction rate were decreased with increase of lengths of alkyl groups. It seems due to steric effect of alkyl groups of R-BI

Effect of Cationic Micellar Aggregates on the Kinetics of Dextrose Oxidation by N-Bromophthalimide

The effect of cationic micelles of Cetyltrimethyl ammonium bromide (CTAB) on the kinetics of oxidation of dextrose by N-Bromophthalimide were studied at 40°C. The reaction follows fractional-order and first order kinetics, with respect to [dextrose] and [NBP], respectively. CTAB strongly catalyze the reaction, and typical kobs and [CTAB] profile was observed, that is, with a progressive increase in [CTAB], the reaction rate increased, reaches a maximum value then decreased. Results are treated quantitatively in terms of Berezin's Model, which is applicable to bimolecular micellar catalyzed reaction. There is a negative effect of mercuric acetate and phthalimide. The influence of salts on the reaction rates has also been seen. The activation parameters as well as other parameters were calculated and suitable mechanism consistent with the experimental findings has been proposed.

음이온 및 양이온 미셀 용액에서 친핵체에 의한 유기 포스피네이트의 탈인산화반응

In the aqueous solutions the dephosphorylations of isopropyl phenyl-4-nitrophenyl phosphinate(IPNPIN) mediated by hydroxide and o-iodosobenzoate ions ate relatively slow, because of hydrophobicity of the substrate, and however it appears that is inherently better nucleophile than , which is more soft ion. On the other hand, in cetyltrimetyiammonium bromide(CTABr) solutions which contain cationic micelles, the dephosphorylations of IPNPIN mediated by or ate very accelerated to 120 or 100,000 times as compared with those in the aqueous solutions. The values of pseudo first order rate constants reach a maximum with increasing. Such rate maxima are typical of micellar catalysed bimolecular reactions and the rise in rate constant followed by a gradual decrese is characteristic of reactions of hydrophobic substrates. In the cationic micellar solutions of CTABr, accelerates the reactions much more than that does. The reason seems that which is more hydrophobic and soft ion than is more easily moved into the Stern layer of the CTABr micelles than . In the anionic micellar solutions of sodium dodecyl sulfate(SDS), the dephosrhorylations of IPNPIN ate slower than those in aqeous solutions. It means that or cannot easily move and approach to the Stern layer of the micelle in which almost all the hydrophobic substrate are located and which has a negative circumstance.

Effect of cationic micellar aggregates on the kinetics of oxidation of aminoalcohols by N-bromosuccinimide in alkaline medium

The kinetics of oxidation of some aminoalcohols (AA), viz. ethanolamine, diethanolamine, and triethanolamine, by N-bromosuccinimide (NBS) in alkaline medium has been investigated in the absence as well as in the presence of cetyltrimethylammonium bromide (CTAB), a cationic surfactant. The reaction always followed a first-order dependence of rate on NBS, while the order in each AA and alkali was found to decrease from unity to zero at higher [AA] and [OH −], respectively. The reaction is strongly catalyzed by CTAB even before the critical micelle concentration (CMC) of CTAB. However, the observed rate constants attained constancy at higher [CTAB] (>CMC of CTAB). The premicellar kinetics has been rationalized in the light of the Piszkiewicz positive cooperativity model [J. Am. Chem. Soc. 99 (1977) 1550]. The binding constants between the reactants and the surfactant have also been evaluated using the Raghvan and Srinivasan model [Proc. Ind. Acad. Sci. 98 (1987) 199], which is applicable to bimolecular micellar catalyzed reaction and predicts constancy in the observed rate constant at higher [surfactant]. The binding constants obtained by both the models are in good agreement.

Kinetis of the reaction of alkaline hydrolysis of thiophosphates in micellar and hexagonal phases of the cetyldimethylethylammonium bromide/NaOH/water system.

Abstract Reactivity of O-p-nitrophenyl-O,O-dimethylthiophosphate ( A ), O-p-nitrophenyl-O,O-diethylthiophosphate ( B ) and O-p-nitrophenyl-O,O-dimethylphosphate ( C ) in alkaline hydrolysis in the cetyldimethylethylammonium bromide (CDAB)/NaOH/water system in micellar (MI) and and hexagonal (E) phases was investigated with the help of the spectrophotometrical method. Kinetic parameters of micellar-catalysed reactions (binding constants and rate constants in micellar pseudophase) are defined from kinetic dependence k obs = f(C CDAB ) in accordance with the pseudophase model. The formation of micelles results in maximum acceleration of the alkaline hydrolysis A and C by 6 and 8 times. The reaction becomes slower in an ordered E-phase in comparison with the Mi-phase for A, B and C by 16, 18 and 9 times, accordingly. The process is inhibited 3 and 5 times accordingly in comparison with aqueous alkaline hydrolysis in the E phase for A and B .

Kinetic study and analytical applications of micellar catalyzed reactions of 1-fluoro-2,4-dinitrobenzene with inorganic thioanions using a fluoride-selective electrode

A kinetic study and analytical applications of the CPC micellar catalyzed reactions of 1-fluoro-2,4-dinitrobenzene (FDNB) with inorganic thioanions (sulfide, sulfite and thiosulfafte) using a fluoride-selective electrode is described. Reaction orders (unity for both FDNB and thioanion) and experimental stoichiometric reaction-rate constants were calculated from initial slope measurements (Δ E/Δ t) at various pH values (4–9). Calibration graphs for quantitative determinations (4.5–45 μM for sulfide, 2.4–75 μM for thiosulfate and 6.6–75 μM for sulfite) are constructed using the initial rate approach. The proposed method has been applied to the determination of sulfide in spiked seawater samples using the multiple standard addition approach with a mean relative error of 5.5%. The application of this micellar catalyzed reaction in the differential kinetic analysis of binary mixtures of sulfide–thiosulfate and sulfite–thiosulfate, using the proportional equations approach at pH 5.5 and 8.0, was unsuccessful due to the interactions of the two analytes, which can be explained using the ion-exchange/pseudophase model of micellar catalysis. However, the use of multiple linear regression approach on a sufficient number of standard binary mixtures can confront this drawback.

Application of the Pseudophase Ion Exchange Model to a Micellar Catalyzed Reaction in Water−Glycerol Solutions

The experimental results obtained for the hydrolysis of p-nitrophenyldiphenyl phosphate (NPDPP) in the presence of sodium hydroxide (NaOH), micelles of cetyltrimethylammonium bromide (CTAB), and aqueous solutions of glycerol are described in terms of the pseudophase ion-exchange model (PPIE). The effect of glycerol on micelle formation and its influence on the reaction medium are also discussed. The results obtained indicate that the PPIE model is applicable for micellar catalysis in water−glycerol solutions.

Micellar-catalyzed reactions of a phosphate ester: effect of the dielectric constant of the medium

The hydrolysis of p-nitrophenyl diphenyl phosphate was studied in aqueous solutions containing micelles of cetyltrimethylammonium bromide (CTAB), sodium hydroxide and various concentrations of dimethylsulfoxide (DMSO). Pseudo first-order ( k ψ) and second-order ( k 2) rate constants were determined at 15, 25 and 35°C and activation parameters were also measured. The rate profiles obtained for solutions containing 10–50% DMSO by volume exhibited clear maxima that shifted to higher concentrations of CTAB as a function of DMSO added. For solutions containing 60–80% DMSO by volume there was no maximum in the rate profile and the reaction was inhibited. Solutions containing 90% DMSO by volume exhibited much higher reaction rates and considerably more catalysis. In the absence of surfactant a linear relationship is obtained between log k ψ and the Lorentz function of the dielectric constant of the binary mixtures DMSO–H 2O. When CTAB is added to the reaction medium there are two different situations. Beyond the formation of the hydrate DMSO·2H 2O, which inhibits the CTAB micellization, the results are identical to those obtained in the systems with no surfactant. However, in presence of CTAB micelles, the linear relationship between log k ψ and f( ε) was quite different from that in the other two cases. These results show that a macroscopic property such as the dielectric constant of the medium may be used to describe the effect of DMSO on the hydrolysis rates either in absence of surfactant or when this is dissolved as the monomer, but not in the presence of micellized surfactant.

Kinetic evidence for temperature-induced demixing of a long chain dioxolane in aqueous micellar solutions of sodium dodecyl sulfate: a new application of the pseudophase ion exchange model

The effect of anionic micelles of sodium dodecyl sulfate (SDS) on the rates of acid-catalyzed hydrolyses of 2-(p-alkoxyphenyl)-1,3-dioxolanes with alkoxy groups of different chain lengths, methoxy (p-MPD), nonoxy (p-NPD), and tetradecoxy (p-TPD), were determined as a function of SDS and NaCl concentrations and temperature. First-order rate constants, k obs , were obtained from plots of ln(A∞-A) vs time that were linear for at least three half-lives. The k obs -[SDS] profiles were fitted by using the pseudophase ionexchange (PPIE) model and substrate binding constants, K s , and second-order rate constants for reaction in the micellar pseudophase, k 2m , were estimated from the simulations. Values of K s and k 2m for p-MPD and p-NPD are completely consistent with micellar effects on other acid-catalyzed hydrolyses in SDS and the assumptions of the PPIE model ; i.e. hydrolysis of monomeric substrate occurs in either the aqueous or the micellar pseudophases. However, kinetic profiles for p-TPD in SDS are more consistent with this substrate acting as a nonionic surfactant that does not mix ideally with SDS. The K s for p-TPD decreases about 800-fold as the temperature is increased from 25 to 50 °C. In 0.012 M SDS, k obs for p-TPD passes through a sharp maximum at 32 °C with increasing temperature whereas the plot for p-NPD is linear. At constant SDS concentration, added Nacl initially speeds the hydrolysis of p-TPD instead of inhibiting the reaction as observed for p-NPD and salt effects on other micellar-catalyzed reactions. All these results can be interpreted by assuming that increasing the temperature induces demixing of p-TPD and SDS to give two populations of mixed micelles each enriched in one of the surfactants and in dynamic equilibrium. Thus the PPIE model can be used to identify nonrandom distributions of reactive and nonreactive surfactants in aggregated systems.

Micellar-catalysed reactions for flow injection systems. Determination of pyridoxal-5-phosphate

A flow injection spectrofluorimetric procedure is proposed for the determination of pyridoxal-5-phosphate in a micellar medium based on its cyanide-catalysed oxidation by oxygen. In the presence of cetyltrimethylammonium bromide, the reaction rate increases by a factor of 3.6 and the pH of maximum fluorescence is also modified. This makes it possible to obtain greater selectivity in the determination.

Micellar catalyzed redox reactions of bilirubin in CTAB medium. A pulse radiolysis study

AbstractThe reaction of CO with bilirubin which is not detectable in homogeneous aqueous medium proceeds almost with diffusion controlled rate in CTAB micellar system. This could be explained on the basis of catalysis caused by the possible electrostatic surface potential of cationic CTAB Micelles. The rate constant for the oxidation of bilirubin by haloperoxyl radicals have been shown to increase with increasing solvent polarity. Although the polarity effect was small, it followed a trend in the expected direction. Micellar effect was not observed in the oxidation reactions when alcohol was present in high concentration. But a small increase in the rate constant was observed when alcohol concentration was lower. © 1994 John Wiley &amp; Sons, Inc.

Kinetic study and analytical applications of the micellar catalysed reactions of 1-fluoro-2,4-dinitrobenzene with thiols using a fluoride-selective electrode

A kinetic study and analytical application of the micellar catalysed reaction of several thiols (thioglycolic, mercaptopropionic, mercaptosuccinic and thiobenzoic acids, thioglycerol and thiophenol) with 1-fluoro-2,4-dinitrobenzene (FDNB) using a fluoride-selective electrode is described. The effect of various types of surfactants, cetyltrimethylammonium bromide (CTAB), cetylpyridinium chloride (CPC), Tween 80 and sodium dodecyl sulfate, on the electrode behaviour and the reaction rate was systematically studied. Cationic surfactants (CTAB, CPC) showed a considerable acceleration of the reaction rate (up to 684 times). Reaction orders (unity for both FDNB and thiol) and experimental stoichiometric reaction-rate constants in the presence of CPC were calculated from initial slope measurements (ΔE/Δt). Calibration graphs for quantitative determinations in micromolar to millimolar concentration ranges were constructed using the fixed-time method (10ΔE/S–1 versus c). The proposed method allows measurements in highly coloured or turbid solutions. Results obtained for the determination of thioglycolic acid in commercial hair cold-wave suspensions and depilatory cream compare favourably with those given by the reference iodimetric titration method. Automation of the method can be achieved by using flow injection with a fluoride flow-through electrode as detector.

Ultrasonic Absorption Studies of the Micellar Catalyzed Reaction of the Base Dissociation of Ammonia

Abstract The base dissociation of ammonia has been studied by an ultrasonic absorption method in both the absence and presence of SDS micelle in aqueous solution, and kinetic parameters were obtained. The micellar catalyzed reaction mechanism, including the interactions of ammonium ion with SDS micelles, are discussed.

Kinetic-potentiometric study and analytical applications of micellar-catalysed reactions of 1-fluoro-2,4-dinitrobenzene with amino compounds

The effect of various surfactants on the reaction of 1-fluoro-2,4-dinitrobenzene (FDNB) with amino compounds is examined by using the fluoride-selective electrode. Micellar catalysis was provided by cetyltrimethylammonium bromide (CTABr), Aerosol OS, 22N and 501 and Triton X-405 even at levels below the critical micelle concentration. The micellar catalysis of CTABr in the reactions of 13 amino acids is described and correlation with the structure of the amino acids is discussed. Micellar (CTABr) catalysis of the reaction of FDNB with slowly reacting amines (cephalexin, 2-amino-2-thiazole, sulphamethizole, dopamine and 2-thiobarbituric and 5-nitrobarbituric acids) is described and a kinetic-potentiometric determination (initial slope or fixed time) is proposed for these compounds at concentrations of 10 −4−10 −2 M. The surfactants mentioned can also be determined on the basis of their catalytic effect on the slow reaction of phenylalanine with FDNB. The micellar-catalysed kinetic method is satisfactory for the determination of cephalexin, sulphamethizole and CTABr in pharmaceutical formulations. The fluoride- selective electrode is shown to be useful for studying the liberation of fluoride by organic reactions in micellar systems.

Micellar-catalyzed reactions for flow-injection systems : Determination of pyridoxal

The advantages of applying the solubilization and catalytic properties of aqueous micelle solutions to reactions taking place in flow-injection systems are demonstrated. The reaction of pyridoxal (a B 6 vitamin) with cyanide was investigated in both aqueous and micellar cetyltrimethylammonium bromide (CTAB) solution. Higher sensitivities and lower limits of detection were obtained for the micellar carrier, with the pseudo-first-order reaction rate increasing by a factor of two in 0.05 M CTAB relative to water carrier. Because the micellar aggregates also increase fluorescence quantum yields, use of fluorescence detection gave further signal enhancement, with the limit of detection lowered by a factor of three. Measurement of dispersion in the two systems was also investigated and compared. A new method of characterizing dispersion in flow-injection systems, based on moment analysis of exponentially modified Gaussian peak shapes, is described.