Micellar catalysis in mixed anionic/cationic surfactant systems

Favaro, Yvette L.; Reinsborough, Vincent C.

doi:10.1139/v94-310

Cited by 18 publications

(9 citation statements)

References 11 publications

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“…4 It has been used as a probe reaction for metal ion reactivities and kinetic studies in micelle solutions. [5][6][7][8][9][10][11][12][13][14][15] It has also been used as a model for metal-ion extraction in surfactant self-assembly systems. [16][17][18] Most complex-formation reactions of divalent first row transition metal ions are too fast to be studied by the stopped-flow method, but Ni 2+ reacts more slowly and can therefore be studied in this way.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic information from volume profiles for water exchange and complex-formation reactions of aquated Ni(II). pH, buffer and medium effects

et al. 2009

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Rate and activation parameters for the complex-formation reaction of Ni(2+) with 4-(2-pyridylazo)-N,N-dimethyl aniline (PADA) were studied as a function of pH in different buffers in both aqueous and sodium dodecyl sulfate (SDS) micelle solutions. In aqueous Tris buffer solution, the forward and backward rate constants increased with increasing pH, while the complex-formation constant decreased due to a larger increase in the backward rate constant. The activation entropy, DeltaS(#), and activation volume, DeltaV(#), changed with increasing pH from positive to negative values, suggesting an apparent changeover from a dissociative to a more associative mechanism. Complex-formation reactions with 2,2'-bipyridine in Tris buffer showed almost no increase in the forward and backward rate constants on increasing the pH, but the DeltaS(#) and DeltaV(#) values became more negative. N-ethylmorpholine buffer showed no pH effect on the rate constants and activation parameters. Water exchange reactions of aquated Ni(2+) were also studied as a function of pH under the same conditions. The reported rate and activation parameters for water exchange in Tris and N-ethylmorpholine buffers are consistent with those found for the complex-formation reactions of Ni(2+) with PADA. The observed pH and buffer effects for both the complex-formation and water exchange reactions of aquated Ni(2+) can be accounted for in terms of the formation of a Ni(2+)-Tris complex in Tris buffer and general base catalysis by the buffer components. In SDS micelle solution, the complex-formation reaction with PADA was much faster than in aqueous solution, but the increase in rate constant with increasing pH was less significant, while DeltaS(#) and DeltaV(#) became more positive, pointing to a more dissociative mechanism. For SDS micelle solutions there was no effect on the water exchange rate constant or activation volume. Mechanistic interpretations are offered for all observed pH, buffer and medium effects.

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Section: Introductionmentioning

confidence: 99%

Mechanistic information from volume profiles for water exchange and complex-formation reactions of aquated Ni(II). pH, buffer and medium effects

et al. 2009

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Section: Introductionmentioning

confidence: 99%

“…The use of micellar systems as reactions media has been broadly studied because of the ability they have to modify the rates and selectivity of reactions and also their ability to solubilize organic substrates. [3][4][5] These systems are widely used in emulsion polymerization reactions, [6] as replacement of volatile organic solvents, templates in the synthesis of new materials (specially nanoparticles), [7,8] and as enzyme models. [9][10][11] In some cases, it has been observed that the use of micellar media results in different products than those obtained in homogeneous media, [12] and there are some reports of enantioselective reactions in the presence of sugar-derived surfactants.…”

Section: Introductionmentioning

confidence: 99%

Hydrolysis of phenyl trifluoroacetate in mixed surfactant systems

Torres

Rossi

Fernández

2016

J of Physical Organic Chem

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The rate of spontaneous hydrolysis of phenyl trifluoroacetate (1) was measured in pure and mixed fluorocarbon/hydrocarbon surfactant systems. The reaction is inhibited by the surfactants when their concentrations are higher than the critical micelle concentration. The same behavior is observed in mixtures of surfactants. The kinetic analysis according to the pseudophase separation model indicates that the contribution of the micelle‐associated substrate hydrolysis rate to the overall observed rate constant is negligible. In that condition, the substrate is less available for water. The differences in inhibition observed for the hydrolysis reaction of 1 in the studied systems are due to the contribution of several effects: differences in polarity of the interfaces, protection of the substrate (reactive center) inside the micelles, and stabilization of the transition state. The association constants of 1 with the surfactants and their mixtures were also determined. Copyright © 2016 John Wiley & Sons, Ltd.

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“…An oppositely charged drugsurfactant pair was selected in order to obtain strong synergistic effects relative to the properties of the individual components in the mixture. 12 Thus, the c.m.c. is generally considerably lower for the oppositely charged mixture than for either the drug or surfactant alone.…”

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confidence: 95%

Determination of antihistamines based on the formation of mixed aggregates with surfactants

Andreacute

Sicilia²,

Rubio³

et al. 1998

Analyst

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The determination of antihistamines based on the measurement of the critical micelle concentration (c.m.c.) of mixed sodium dodecyl sulfate (SDS)-antihistamine aggregates is proposed. The dye Coomassie Brilliant Blue G (CBBG) was used as a photometric probe for the rapid determination of c.m.c.s. The micellar properties of these drugs permitted the determination of diphenhydramine, antazoline, tripelennamine, diphenylpyraline and clemizole at the micron level with detection limits ranging between 0.1 and 0.7 microns. Hence the proposed method surpassed existing alternative photometric methods used routinely in the quality control of these drugs in sensitivity and featured similar detection limits to fluorimetric methods. The relative standard deviation for 6 micron diphenhydramine was 3.7%. The method was applied to the determination of these drugs in pharmaceutical preparations (solutions, capsules, creams and pills). which were analyzed directly after dissolution of the samples in distilled water.

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Micellar catalysis in mixed anionic/cationic surfactant systems

Cited by 18 publications

References 11 publications

Mechanistic information from volume profiles for water exchange and complex-formation reactions of aquated Ni(II). pH, buffer and medium effects

Mechanistic information from volume profiles for water exchange and complex-formation reactions of aquated Ni(II). pH, buffer and medium effects

Hydrolysis of phenyl trifluoroacetate in mixed surfactant systems

Determination of antihistamines based on the formation of mixed aggregates with surfactants

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