Micellar medium effects on the hydrolysis of phenyl chloroformate in ionic, zwitterionic, nonionic, and mixed micellar solutions

Muñoz, Marı́a A.; Rodrı́guez, Amalia; Graciani, Marı́a del Mar; Moyá, Marı́a Luisa

doi:10.1002/kin.10067

Cited by 29 publications

(23 citation statements)

References 43 publications

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“…1 Similarly, the hydrolysis of phenyl chloromethanoate is not nearly as much retarded in salt solutions as in micellar solutions. 16 Another indication is the failure of 3, a hydrolytic probe that is particularly sensitive to hydrophobic interactions, to show a relation between the charge of the Stern region and the rate-retarding effect, 1 as was also observed by others for the hydrolysis of 4-nitrophenyl 2,2-dichloropropanoate. 25,26 If the E T (30) probe is a good micropolarity reporter, the micropolarity of the micellar Stern region is considerably lower than expected on the basis of the concentrated salt solutions used as mimics of the Stern region.…”

Section: An Extended Model Of the Micellar Stern Regionmentioning

confidence: 71%

The Nature of the Micellar Stern Region As Studied by Reaction Kinetics. 2^,¹

et al. 2004

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The nature of rate-retarding effects of cationic micelles on the water-catalyzed hydrolyses of a series of para-substituted 1-benzoyl-1,2,4-triazoles (1a-f) and 1-benzoyl-3-phenyl-1,2,4-triazole (2) has been studied using kinetic methods. A comparison is drawn between medium effects in the micellar Stern region and in model solutions for the micellar Stern region. Simple model solutions involving concentrated aqueous solutions of a small ionic molecule resembling the surfactant headgroup, as reported before,(1) were improved. New model solutions for alkyltrimethylammonium bromide micelles contain both tetramethylammonium bromide (TMAB), mimicking micellar headgroups, and 1-propanol, mimicking hydrophobic tails. The rate-retarding effect of micelles on the hydrolysis of 1a-f and 2 is caused by the high concentration of headgroups as well as by hydrophobic tails in the Stern region where 1a-f and 2 bind to the micelle. Individual contributions of these interactions are quantified. Rate-retarding effects found for different probes, with different sensitivities for interactions as they occur when the probe binds to the micellar Stern region, as well as the micellar Stern region's micropolarity as reported by the E(T)(30) probe, are satisfactorily reproduced by new model solutions containing both TMAB and 1-propanol.

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Section: An Extended Model Of the Micellar Stern Regionmentioning

confidence: 71%

The Nature of the Micellar Stern Region As Studied by Reaction Kinetics. 2^,¹

et al. 2004

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“…The rates of chemical reactions are known to be changed by self-organized assemblies such as micelles [1][2][3][4][5][6][7][8][9]. Effects of micelles on these reactions can be attributed to electrostatic and hydrophobic interactions.…”

Section: Introductionmentioning

confidence: 98%

Kinetics of brilliant green fading in the presence of TX-100, DTAB and SDS

Samiey

Dargahi

2010

Reac Kinet Mech Cat

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The rate constant of alkaline fading of brilliant green (BG ? ) was measured in the presence of non ionic (TX-100), cationic (DTAB) and anionic (SDS) surfactants. This reaction was studied under pseudo first-order conditions at 283-303 K. The rate of reaction showed remarkable dependence on the electrical charge of the used surfactants. It was observed that the reaction rate constant increases in the presence of TX-100 and DTAB (catalytic effect) and decreases in the presence of SDS (inhibitory effect). Binding constants and the related thermodynamic parameters were obtained by the classical model. The results show that binding of BG ? to TX-100 is exothermic and binding of BG ? to DTAB and SDS is endothermic in the used concentration range of surfactants.

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“…45,86 In our model, the effects of ionic strength and direct ionic interactions are modeled by NMS. As argued above, the rate-retarding effects exerted in solution 2 by NMS on hydrolysis of probes 1aÀf cannot be attributed to a contribution of NMS to the decrease in polarity.…”

Section: ' Results and Discussionmentioning

confidence: 99%

The Nature of the Sodium Dodecylsulfate Micellar Pseudophase as Studied by Reaction Kinetics

Onel

Buurma

2011

J. Phys. Chem. B

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The nature of the rate-retarding effects of anionic micelles of sodium dodecyl sulfate (SDS) on the water-catalyzed hydrolysis of a series of substituted 1-benzoyl-1,2,4-triazoles (1a-f) has been studied. We show that medium effects in the micellar Stern region of SDS can be reproduced by simple aqueous model solutions containing small-molecule mimics for the surfactant headgroups and tails, namely sodium methyl sulfate (NMS) and 1-propanol, in line with our previous kinetic studies for cationic surfactants ( Buurma et al. J. Org. Chem. 2004 , 69 , 3899 - 3906 ). We have improved our mathematical description leading to the model solution, which has made the identification of appropriate model solutions more efficient. For the Stern region of SDS, the model solution consists of a mixture of 35.3 mol dm(-3) H(2)O, corresponding to an effective water concentration of 37.0 mol dm(-3), 3.5 mol dm(-3) sodium methylsulfate (NMS) mimicking the SDS headgroups, and 1.8 mol dm(-3) 1-propanol mimicking the backfolding hydrophobic tails. This model solution quantitatively reproduces the rate-retarding effects of SDS micelles found for the hydrolytic probes 1a-f. In addition, the model solution accurately predicts the micropolarity of the micellar Stern region as reported by the E(T)(30) solvatochromic probe. The model solution also allows the separation of the individual contributions of local water concentration (water activity), polarity and hydrophobic interactions, ionic strength and ionic interactions, and local charge to the observed local medium effects. For all of our hydrolytic probes, the dominant rate-retarding effect is caused by interactions with the surfactant headgroups, whereas the local polarity as reported by the solvatochromic E(T)(30) probe and the Hammett ρ value for hydrolysis of 1a-f in the Stern region of SDS micelles is mainly the result of interactions with the hydrophobic surfactant tails. Our results indicate that both a mimic for the surfactant tails (NMS) and a mimic for the surfactant headgroups (1-propanol) are required in a model solution for the micellar pseudophase to reproduce all medium effects experienced by a variety of different probes.

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Micellar medium effects on the hydrolysis of phenyl chloroformate in ionic, zwitterionic, nonionic, and mixed micellar solutions

Cited by 29 publications

References 43 publications

The Nature of the Micellar Stern Region As Studied by Reaction Kinetics. 2^,¹

The Nature of the Micellar Stern Region As Studied by Reaction Kinetics. 2^,¹

Kinetics of brilliant green fading in the presence of TX-100, DTAB and SDS

The Nature of the Sodium Dodecylsulfate Micellar Pseudophase as Studied by Reaction Kinetics

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Micellar medium effects on the hydrolysis of phenyl chloroformate in ionic, zwitterionic, nonionic, and mixed micellar solutions

Cited by 29 publications

References 43 publications

The Nature of the Micellar Stern Region As Studied by Reaction Kinetics. 2,1

The Nature of the Micellar Stern Region As Studied by Reaction Kinetics. 2,1

Kinetics of brilliant green fading in the presence of TX-100, DTAB and SDS

The Nature of the Sodium Dodecylsulfate Micellar Pseudophase as Studied by Reaction Kinetics

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The Nature of the Micellar Stern Region As Studied by Reaction Kinetics. 2^,¹

The Nature of the Micellar Stern Region As Studied by Reaction Kinetics. 2^,¹