Effect of Cetyltrimethyl Ammonium Bromide on the Kinetics of Iodination of Aniline by Iodine (original) (raw)
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Efiect of substitution on aniline in inducing growth of anionic micelles
Small-angle neutron scattering (SANS) measurements were carried out on sodium dodecyl sulfate (SDS) micelles in the presence of three different hydrophobic salts, i.e. aniline hydrochloride, o-toluidine hydrochloride and m-toluidine hydrochloride. All these salts induce a uniaxial growth of micelles to form prolate ellipsoidal structures. A progressive decrease in the surface charge of the micelles was observed with the addition of salts followed by a rapid growth of the micelles. The presence of a methyl substitution at the ortho position of aniline does not alter the growth behavior significantly. However, when the substitution is at meta position micellar growth is favored at lower salt concentration than that is observed for aniline. This can be explained in terms of the difference in the chemical environments of the substituents at the ortho and meta positions.
Effect of substitution on aniline in inducing growth of anionic micelle
Pramana-journal of Physics, 2004
Small-angle neutron scattering (SANS) measurements were carried out on sodium dodecyl sulfate (SDS) micelles in the presence of three different hydrophobic salts, i.e. aniline hydrochloride, o-toluidine hydrochloride and m-toluidine hydrochloride. All these salts induce a uniaxial growth of micelles to form prolate ellipsoidal structures. A progressive decrease in the surface charge of the micelles was observed with the addition of salts followed by a rapid growth of the micelles. The presence of a methyl substitution at the ortho position of aniline does not alter the growth behavior significantly. However, when the substitution is at meta position micellar growth is favored at lower salt concentration than that is observed for aniline. This can be explained in terms of the difference in the chemical environments of the substituents at the ortho and meta positions.
Journal of Colloid and Interface Science, 1996
aqueous solutions (11) and reverse micelles in organic sol-The partition constants (K p ) of iodine between sodium dodecylvents (12,. Regarding the effect of anionic micelles in sulfate micelles and the external media have been measured in the aqueous solutions, few studies can be mentioned. Ross and presence of water-soluble (sodium sulfate) and micelle-soluble ( n-Oliver (1) and Chao et al. (14) have reported that only a hexane and n-hexanol) additives. A spectrophotometric method very weak interaction takes place between iodine and negabased in the analysis of the alterations provoked by the presence tively charged micelles, and Chang et al. (15) have reported of the surfactant plus the additives upon the reversible reaction on an acceleration of the hydrolysis of tri-iodide ion by taking place between iodine and iodide to give tri-iodide ions was anionic micelles. employed (Abuin, E., and Lissi, E., J. Chem. Ed. 69, 340 (1992)).
Effect of substitution on aniline in inducing growth of anionic micelles
Pramana-journal of Physics, 2004
Small-angle neutron scattering (SANS) measurements were carried out on sodium dodecyl sulfate (SDS) micelles in the presence of three different hydrophobic salts, i.e. aniline hydrochloride,o-toluidine hydrochloride andm-toluidine hydrochloride. All these salts induce a uniaxial growth of micelles to form prolate ellipsoidal structures. A progressive decrease in the surface charge of the micelles was observed with the addition of salts followed by a rapid growth of the micelles. The presence of a methyl substitution at the ortho position of aniline does not alter the growth behavior significantly. However, when the substitution is at meta position micellar growth is favored at lower salt concentration than that is observed for aniline. This can be explained in terms of the difference in the chemical environments of the substituents at the ortho and meta positions.
Micelles. Structure and catalysis
Recueil des Travaux Chimiques des Pays-Bas, 2010
* To whom correspondence should be addressed. hble I Amphiphiles and micelle parameters. Amphiphile Cetyltrimethylammonium bromide (CTAB) Sodium dodecyl sulphate (SDS) 4-(Dodecyldimethylammonio)butyrate Polyoxyethylene (20) mono(p-nonylpheny1)ether (Igepal CO-850) ' For comprehensive reviews and discussions, see: "Micellization,
Kinetic and spectroscopic investigations of aqueous micelles of cationic surfactants
Central European Journal of Chemistry, 2010
Aqueous micelles can exert a medium effect both on spontaneous and non-spontaneous reactions [1][2][3][4].In bimolecular reactions, the concentration effect influences the observed rate constant (k obs ) because the reactants can be brought together at the micellar surface, or kept apart. This effect is independent of reaction medium, so micellar rate effects have to be treated in terms of models that estimate partitioning of the two reagents between water and micelles and second order rate constants in each pseudophase. To apply these models, the reagent concentration has to be estimated in the micellar pseudophase, even if the volume available to the reactant is uncertain. Sometimes it is possible to measure reagent partitioning but often it is calculated by using equations that contain parameters whose values are uncertain [2], and comparison between second order rate constants that differ by less than an order of magnitude is not very meaningful. On the other hand, comparing first order rate constants is more significant because they are independent of reaction volume.
Journal of Physical Organic Chemistry, 1991
Two amphiphilic oximes, 10-phenyl-10-hydroxyiminodecanoic acid (oxime 11) and 4-(9-carboxynonanyl)-l-(9-carhoxy-1-hydroxyimino nonany1)benzene (oxime 111) were synthesized. The pK. values of oximes I1 and I11 and acetophenoxime (oxime I) and the rates of oximolysis of p-nitrophenyl acetate (NPA) and p-nitrophenyl octanoate (NPO) were determined in the presence and absence of micellar hexadecyltrimethylammonium bromide (CTAB). The rates of oximolysis increased by up to 3 x 104-fold in the presence of CTAB. Quantitative analysis of micellar effects, using an ion-exchange pseudo-phase model, allowed the determination of the second-order rate constants for the reactions of oximes 1-111 with NPA and NPO in the micellar pseudo-phase. The calculated rate constants in the micellar pseudo-phase were lower than those in water, demonstrating that the rate enhancements were due to substrate concentration in the micelles. Comparison of the rate constants in micelles and water suggests that the sites of reaction of oximes 1-111 with NPO and NPA are similar to those in hulk aqueous solution. Micellar incorporation of the hydrophobic oximes I1 and I11 does not lead to a major change in the nucleophilicity of the oximate anion.
Counterion specificity of the micelle surface and its implications on micellar catalysis
Colloid & Polymer Science, 1996
Dodecyltrimethylammonium bromide-Dodecyltrimethylammonium hydroxide-water mixtures were studied with ionselective electrodes, and the aggregation behavior, degree of ionization of the micelles and the distribution constants of bromide and hydroxide ions between water and micelles were found, showing that some suppositions about the interpretation of micellar catalysis are incorrect, and these interpretations must be revised. The results support the mass action model for the theoretical treatment of micellar catalysis.
Micellar effects upon alkene bromination. The role of micellar charge
The Journal of Organic Chemistry, 1987
The observed effects of aqueous micelles on overall rates of alkene bromination (Lennox, R. B.; McClelland, R. A. J. Am. Chem. SOC. 1986,108,3771) are due largely to a micellar charge effect and to a change in the equilibrium between Br2 and Br3-. In micelles of cetyltrimethylammonium bromide (CTABr) the equilibrium favors the less reactive Brs-, and overall reaction is therefore slower than in nonionic micelles of Brij 35 or in anionic micelles of sodium dodecyl sulfate (SDS). Addition of (n-Bu)4NBr to anionic or nonionic micelles perturbs their surface, which assists binding of anions, e.g., Bror Br3-, and slows reaction. Variations of TI relaxation times for *lBr show that Br-interacts with the polyoxyethylene residues of nonionic micelles, and there is qualitative evidence for binding of Brato Brij 35.