Study of the reaction 1-methoxy-4-(methylthio)benzene + IO4-: importance of micellar medium effects

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

doi:10.1039/b102179f

Cited by 6 publications

(17 citation statements)

References 23 publications

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“…The second-order rate constant for the reaction in water was 1.51 dm 3 mol -1 s -1 , in good agreement with the literature value 1.55 dm 3 mol -1 s -1 . The kinetic data obtained in SDS micellar solutions are also in good agreement with those in a previous work 8b…”

Section: Methodssupporting

confidence: 90%

“…Assuming that Beer's law is obeyed, one can write where A is the observed absorbance and A w and A m are the absorbances in water and of fully bound organic substrate, respectively. In the case of ArSMe, A m could not be measured directly because of the relatively low binding of this organic substrate to micellar aggregates, as indicated previously by Bunton et al 8a-c To estimate K m without the measurement of A m the following equation was considered: The experimentally accessible terms of eq 3 are A , A w , and [surfactant m ]. This equation was used to estimate the equilibrium binding constants of ArSMe by registering the changes in absorbance at 260 and 265 nm and by fitting these data using eq 3.…”

Section: Methodsmentioning

confidence: 99%

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Conductometric, Surface Tension, and Kinetic Studies in Mixed SDS−Tween 20 and SDS−SB3-12 Micellar Solutions

et al. 2004

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Micellization in sodium dodecyl sulfate (SDS)-N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate and SDS-polyoxyethylenesorbitan monolaurate binary surfactant solutions was studied by means of conductivity and surface tension measurements. These studies showed that two types of micellar aggregates are present in the mixed micellar solutions. Two reactions were investigated in these micellar media, the oxidation of 1-methoxy-4-(methylthio)benzene by IO(4)(-) and the spontaneous hydrolysis of phenyl chloroformate. Information on the distribution of reagents in the micellar reaction media was obtained through conductivity and spectroscopic measurements. Discussion of the kinetic data showed that the redox reaction takes place mainly in the aqueous phase of the mixed solutions, whereas hydrolysis occurs in the aqueous as well as in the micellar pseudophase. Variations in the observed rate constants of the two processes studied are gradual within the whole surfactant concentration range investigated, revealing little information about the mixed micellar medium.

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Section: Methodssupporting

confidence: 90%

Section: Methodsmentioning

confidence: 99%

Conductometric, Surface Tension, and Kinetic Studies in Mixed SDS−Tween 20 and SDS−SB3-12 Micellar Solutions

et al. 2004

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“…Usually, the kinetic micellar effects observed in bimolecular processes are mainly due to the concentration of one or both reactants in the small volume of the micelles. However, there are processes for which large kinetic micellar effects, not connected to concentration effects, are operative . In the reaction studied, the difference between k 2 w and k 2 m would account for the micellar medium effects in the dimeric micellar solutions assuming that no morphological transition occurs.…”

Section: Resultsmentioning

confidence: 99%

Concentration and Medium Micellar Kinetic Effects Caused by Morphological Transitions

Graciani

Rodrı́guez²,

Martı́n³

et al. 2010

Langmuir

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The reaction methyl naphthalene-2-sulfonate + Br(-) was investigated in several alkanediyl-α-ω-bis(dodecyldimethylammonium) bromide, 12-s-12,2Br(-) (with s = 2, 3, 4, 5, 6, 8, 10, 12), micellar solutions in the absence and in the presence of various additives. The additives were 1,2-propylene glycol, which remains in the bulk phase, N-decyl N-methylglucamide, MEGA10, which forms mixed micelles with the dimeric surfactants, and 1-butanol, which distributes between the aqueous and micellar phases. Information about the micellar reaction media was obtained by using conductivity and fluorescence measurements. In all cases, with the exception of water-1,2-prop 12-5-12,2Br(-) micellar solutions, with 30% weight percentage of the organic solvent, a sphere-to-rod transition takes place upon increasing surfactant concentration. In order to quantitatively explain the experimental data within the whole surfactant concentration range, a kinetic equation based on the pseudophase kinetic model was considered, together with the decrease in the micellar ionization degree accompanying micellar growth. However, theoretical predictions did not agree with the experimental kinetic data for surfactant concentrations above the morphological transition. An empirical kinetic equation was proposed in order to explain the data. It contains a parameter b which is assumed to account for the medium micellar kinetic effects caused by the morphological transition. The use of this empirical equation permits the quantitative rationalization of the kinetic micellar effects in the whole surfactant concentration range.

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“…The same result has been found for other organic substrates 23, 24 and this could be related to the higher hydrophobic character of the micellar pseudophase of sulfobetaine micellar solutions in respect to that of TTAB or CTAB ones. In nonionic micellar solutions, K m increases when the hydrophobic character of the micellar pseudophase increases 10a, 12. In regard to the mixtures SDS/Brij 35 , K m increases in the mixed micellar solutions with X SDS = 0.67 in respect to pure SDS.…”

Section: Resultsmentioning

confidence: 96%

“…No kinetic data in nonionic micellar solutions are shown. However, a way of investigating the importance of the contribution of charge–charge interactions, independently of other micellar medium effects, is to study the reaction in nonionic micellar solutions 10. With this in mind, the spontaneous hydrolysis of phenyl chloroformate was carried out in the nonionic micellar solutions of dodecyl tricosaoxyethylene glycol ether (Brij 35 ) and the esters of long‐chain fatty acids and sorbitan polyethyleneglycol Tween 20, Tween 40, and Tween 80.…”

Section: Introductionmentioning

confidence: 99%

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

Muñoz

Rodrı́guez

Graciani

et al. 2002

Int J of Chemical Kinetics

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The spontaneous hydrolysis of phenyl chloroformate was studied in various anionic, nonionic, zwitterionic, and cationic aqueous micellar solutions, as well as in mixed anionic-nonionic micellar solutions. In all cases, an increase in the surfactant concentration results in a decrease in the reaction rate and micellar effects were quantitatively explained in terms of distribution of the substrate between water and micelles and the first-order rate constants in the aqueous and micellar pseudophases. A comparison of the kinetic data in nonionic micellar solutions to those in anionic and zwiterionic micellar solutions makes clear that charge effects of micelles is not the only factor responsible for the variations in the reaction rate. Depletion of water in the interfacial region and its different characteristics as compared to bulk water, the presence of high ionic concentration in the Stern layer of ionic micelles, and differences in the stabilization of the initial state and the transition state by hydrophobic interactions with surfactant tails can also influence reactivity. The different deceleration of the reaction observed in the various micellar solutions studied was discussed by considering these factors. Synergism in mixed-micellar solutions is shown through the kinetic data obtained in these media.

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Study of the reaction 1-methoxy-4-(methylthio)benzene + IO4-: importance of micellar medium effects

Cited by 6 publications

References 23 publications

Conductometric, Surface Tension, and Kinetic Studies in Mixed SDS−Tween 20 and SDS−SB3-12 Micellar Solutions

Conductometric, Surface Tension, and Kinetic Studies in Mixed SDS−Tween 20 and SDS−SB3-12 Micellar Solutions

Concentration and Medium Micellar Kinetic Effects Caused by Morphological Transitions

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

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