In micellar solution

Surfactants have also been of interest for their ability to support reactions in normally inhospitable environments. Reactions such as hydrolysis, aminolysis, solvolysis, and, in inorganic chemistry, of aquation of complex ions, may be retarded, accelerated, or differently sensitive to catalysts relative to the behavior in ordinary solutions (see Refs. 205 and 206 for reviews). The acid-base chemistry in micellar solutions has been investigated by Drummond and co-workers [207]. A useful model has been the pseudophase model [206-209] in which reactants are either in solution or solubilized in micelles and partition between the two as though two distinct phases were involved. In inverse micelles in nonpolar media, water is concentrated in the micellar core and reactions in the micelle may be greatly accelerated [206, 210]. The confining environment of a solubilized reactant may lead to stereochemical consequences as in photodimerization reactions in micelles [211] or vesicles [212] or in the generation of radical pairs [213]. 

S. A. Safran, Theory of Structure and Phase Transitions in Globular Microemulsions, in Micellar Solutions and Microemulsions, S. H. Chen and R. Rajagopalan, eds.. Springer-Verlag, New York, 1990, Chapter 9. 

Analogously, the effect of micelles on the rate of the unimolecular retro Diels-Alder reaction has been studied. Also here only a modest retardation" or acceleration" is observed. Likewise, the presence of micelles has been reported to have a modest influence on an intramolecular Diels-Alder reaction . Studies on the endo-exo selectivity of a number of different Diels-Alder reactions in micellar media lead to comparable conclusions. Endo-exo selectivities tend to be somewhat smaller in micellar solutions than in pure water, but still are appreciably larger than those in organic media In contrast, in microemulsions the endo-exo selectivity is reduced significantly" ... 

Table 5.4. Apparent second-order rate constants (ycjfp) for the reaction of 5.1c with 5.2 in micellar solutions of Co(DS)2, Ni(DS)2, Cu(DS)2 and Zn(DS)2 compared to the second-order...

In order to obtain more insight into the local environment for the catalysed reaction, we investigated the influence of substituents on the rate of this process in micellar solution and compared this influence to the correspondirg effect in different aqueous and organic solvents. Plots of the logarithms of the rate constants versus the Hammett -value show good linear dependences for all... 

The aim of this work is the development of pyrene determination in gasoline and contaminated soils. For this purpose we used room temperature phosphorescence (RTP) in micellar solutions of sodium dodecylsulphate (SDS). For pyrene extraction from contaminated soils hexane was used. Then exttacts earned in glass and dried. After that remains was dissolved in SDS solution in the presence of sodium sulphite as deoxygenation agent and thallium (I) nitrate as heavy atom . For pyrene RTP excitation 337 nm wavelength was used. To check the accuracy of the procedures proposed for pyrene determining by RTP, the pyrene concentrations in the same gasoline samples were also measured by GC-MS. 

Distribution of benzodiazepines in system micellar pseudophase - water was investigated in micellar solutions of sodium dodecylsulfate. The protonization constants of benzodiazepines were determined by the UV-spectophotometry. Values of protonization constants increase with increasing of sodium dodecylsulfate concentration. The binding constants of two protolytic forms of benzodiazepines with a micellar pseudo-phase and P, values were evaluated from obtained dependence. 

Catalysis and Inhibition in Solutions of Synthetic Polymers and in Micellar Solutions H. Morawetz... 

Mechanisms of micellar reactions have been studied by a kinetic study of the state of the proton at the surface of dodecyl sulfate micelles [191]. Surface diffusion constants of Ni(II) on a sodium dodecyl sulfate micelle were studied by electron spin resonance (ESR). The lateral diffusion constant of Ni(II) was found to be three orders of magnitude less than that in ordinary aqueous solutions [192]. Migration and self-diffusion coefficients of divalent counterions in micellar solutions containing monovalent counterions were studied for solutions of Be2+ in lithium dodecyl sulfate and for solutions of Ca2+ in sodium dodecyl sulfate [193]. The structural disposition of the porphyrin complex and the conformation of the surfactant molecules inside the micellar cavity was studied by NMR on aqueous sodium dodecyl sulfate micelles [194]. 

M. Baviere and T. Rouaud. Solubilization of hydrocarbons in micellar solutions Influence of structure and molecular weight (solubilisation des hydrocarbures dans les solutions micellaires influence de la structure et de la masse moleculaire). Rev Inst Franc Petrol, 45(5) 605-620, September-October 1990. 

Figure 2. Monomer versus overall surfactant concentrations in micellar solutions.

Ben-Shaul, A. and Gelbart, W. M. (1994). Statistical Thermodynamics of Amphi-phile Self-assembly Structure and Phase Transitions in Micellar Solutions. Chapter 1. Springer, Berlin. 

Menadione (vitamin K-3, 79) in ethanol in the presence of oxygen was placed in the sun for 10 min to give the 2,3-epoxide (80) [64]. This has been photolysed in micellar solutions to give two main products 2-hydroxy-3-methylnaphtho-quinone and 2,3-dihydro-2-hydroxy-2-methylnaphthoquinone [65]. Solid menadione left on a south-facing windowsill (in Texas ) for a month gave two photodimers the syn head-to-head and syn head-to-tail cyclobutanes. With UV... 

R = Et) were hydrolysed in micellar solutions of the prepared ketoximes under pseudo-first-order reaction conditions.In the alkaline hydrolysis of / -nitrophenyl ethyl chloromethylphosphonate (254), micellar catalysis by cetylpyridinium bromide is much reduced when KCl and KBr are present. ... 

Gonzalez, J. and Ukrainczyk, L. Transport of nicosulfuron in soil columns. J. Environ. Qua ., 28(1) 101-107, 1999. Gonzalez, V., Ayala, J.H., and Afonso, A.M. Degradation of carbaryl in natural waters enhanced hydrolysis rate in micellar solution. Bull. Environ. Contam. Toxicol, 42(2) 171-178, 1992. 

C. A. Miller, R.-N. Hwan, W.J. Benton, and T.J. Fort Ultralow Interfacial Tensions and Their Relation to Phase Separation in Micellar Solutions. J. Colloid Interface Sci. 61,554(1977). 

Since N will be larger than S+, all anionic surfactants are negatively charged. Similarly, cationic micelles will be positively charged. For instance, the cationic surfactant cetyltrimethyl ammonium bromide (CTAB), we have following equilibrium in micellar solutions ... 

S Terabe, K Otsuka, K Ichikawa, A Tsuchiya, T Ando. Electrokinetic separations in micellar solutions and open-tubular capillaries. Anal Chem 56 111 — 113, 1984. 

AD Harman, RG Kibbey, MA Sablik, Y Fintschenko, WE Kurtin, MM Bushey. Micellar electrokinetic capillary chromatography analysis of the behavior of bilirubin in micellar solutions. J Chromatogr A 652 525—533, 1993. 

The plots of log k vs. log P w and the plots of log k (v) vs. log k (z) were studied for seven cephalosporins. A linear relationship was obtained in micellar solution and in microemulsion solution (Tables 3 and 4). The results obtained indicate that the capacity factor determined by EKC could be used both as parameter to characterize the partition behavior of drugs in ME and MC and as hydrophobic parameter instead of log Pow. k appears to be an evident parameter, and it shows a better diversification than P w. In the 1-octanol/water system, we did not found high values of the partition coefficients. In contrast, the ME systems used provide a better characterization of the drugs according to their hydrophilic/lipophilic properties. 

With respect to the reduced water concentration (1), it seems as if all but one of the hydrolysis reactions following the mechanism shown in Scheme 10 are retarded in micellar solutions (the exception being the hydrolysis of 4-nitrophenyl chloroformate la in cationic micelles ) and the lower water concentration in the micellar Stern region (estimated to be 45 mol dm for and 33 mol dm for SDS ) will... 

Cyanide binding to the hydroxo complex of ferric hemes has been extensively studied in micellar solutions [15-17, 22, 34]. The binding of cyanide is found to be highly dependent on the pH and is maximum at pH 9.6. Optical spectral studies show a distinct isosbestic point at 412 nm for the formation of bis-cyano hemin in SDS from the hydroxo heme. The overall equilibrium is ... 

The temperature dependence (296-330 K) of the ring methyl proton resonances of these monomeric heme complexes in the hydrophobic micellar cavity shows [22] a small deviation from the Curie law as in the low-spin complexes in organic and simple aqueous solvents [1, 52]. The origin of such deviation has been variously ascribed [3, 1, 53] either to aggregation or second order Zeeman (SOZ) effect or presence of low-lying spin-quartet state. Since these low-spin hemes in micellar solutions are in deaggregated form, the deviation may be due to the SOZ and/or presence of low-lying excited state. 

The NMR of ferrous complexes of MPll and MP8 in aqueous SDS solutions has been studied the spectra are very broad and ill-resolved [23]. The heme proton resonances appear in the range 15 to 30 ppm and resemble those of ferrous hemoproteins. The similarity in the linewidths and spectral range of the heme protons in these ferrous peptide complexes with the ferrous hemoproteins suggests that the larger size of the heme peptide restricts the mobility of the molecule inside the micelles compared to that in case of the protoporphyrin complex in micellar solutions, where the spectrum is better resolved. 

A general observation from the HNMR studies on micelle-encapsulated heme is that the line width of the heme protons increases significantly in the micellar solutions compared to those in simple solutions. The change in linewidths of heme methyl protons in micelles is not as large in low-spin Fe(III) hemes as in the high-spin ones. The linewidths in four-coordinate and five-coordinate complexes of ferrous hemes in aqueous micellar solutions are also quite broad compared to those observed in benzene solutions [12, 61], but are similar to those of hemoproteins [2,62]. We examine below the origin and implications of the linewidth change in micellar solutions. 

It is noteworthy that the indenyl complex RuCl(ri -C9H7)(PPh3)2l4 provides an efficient catalyst precursor for the anti-Markovnikov hydration of terminal alkynes in aqueous media, especially in micellar solutions with either anionic (sodium dode-cylsulfate (SDS)) or cationic (hexadecyltrimethylammonium bromide (CTAB)) surfactants [38]. This system can be applied to the hydration of propargylic alcohols to selectively produce P-hydroxyaldehydes, whereas RuCl(Cp)(PMe3)2 gives a,P-unsat-urated aldehydes (the Meyer Schuster rearrangement products)(Scheme 10.8) [39]. 

This model was shown to account for the observed trends of enthalpies, volumes, compressibilities and heat capacities of many types of hydrophobic solutes (hydrocarbons, alcohols and surfactants) In micellar solutions and also for the observed trends for the transfer of hydrophobic solutes to some alcohol-water mixtures. This latter observation supports the view that some alcohol-water mixtures exist as microphases which In many respects resemble micellar systems (11-12). 

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