Effects of anionic micelles on intramolecular general base-catalysed aminolysis of phenyl and methyl salicylates

Khan, M. Niyaz; Dahiru, Mohammad; Na’aliya, J

doi:10.1039/p29890000623

Cited by 11 publications

(5 citation statements)

References 4 publications

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“…The mechanism of oxidation of primary alcohols by permanganate has been studied mostly in alkaline medium although there are some studies of induced oxidation in acid medium [3]. Again surfactants have been found to influence the rates of chemical reactions and a number of such systems have been investigated from the kinetic viewpoint [20][21][22][23][24][25][26][27]. It is, therefore, thought to be of interest to study the kinetics and mechanism of oxidation of methanol and ethanol by permanganate in perchloric acid medium in the absence and presence of Tween-20, a non-ionic surfactant.…”

Section: Introductionmentioning

confidence: 99%

Reductivity of methanol and ethanol towards permanganate in absence and presence of Tween-20 in perchloric acid medium. Mechanism of the oxidation processes

Sen

Samaddar

Das

2005

Transition Met Chem

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The reducing behaviour of methanol and ethanol towards permanganate in perchloric acid medium have been investigated in the absence and presence of the surfactant Tween-20. In the absence of surfactant the reaction is of first order with respect to both oxidant and H + but of complex order in substrate. The alcohol molecule reacts with HMnO 4 to form an intermediate complex which decomposes in the rate-determining step to give the product and Mn v . Effects of urea and acetonitrile on the reaction rate have also been studied. In the presence of Tween-20, the reaction appears to follow Berezin's model where both the oxidant and the substrate are partitioned between the aqueous and the micellar phase and then react. Different thermodynamic and kinetic parameters have been evaluated. The reaction in the presence of the surfactant is entropy-controlled rather than enthalpy-controlled.

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Section: Introductionmentioning

confidence: 99%

Reductivity of methanol and ethanol towards permanganate in absence and presence of Tween-20 in perchloric acid medium. Mechanism of the oxidation processes

Sen

Samaddar

Das

2005

Transition Met Chem

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“…0.005−0.050 M, then the rate of aminolysis of such a substrate can be easily studied without the use of amine buffers. Such reaction characteristics led a few workers to study the effects of ionic micelles on the rates of the nucleophilic substitution reaction of aniline with 2,4-dinitrofluorobenzene and the rates of nitrosation of secondary aliphatic amines by alkyl nitrites. , The effects of sodium dodecyl sulfate (SDS) micelles on the rates of aminolysis of ionized phenyl salicylate (PS - ) have been studied without using amine buffers because the rate of hydrolysis of PS - turned out to be independent of [ - OH] within the [ - OH] range 0.005−0.06 M. , Since the binding constant of PS - with SDS micelles is many-fold smaller than that with cetyltrimethylammonium bromide (CTABr) micelles, we became interested in exploring the effects of CTABr micelles on aminolysis of PS - . The results and their probable explanations for the effects of CTABr micelles on the rates of reactions of PS - with n- butylamine, piperidine, and pyrrolidine are described in this paper.…”

Section: Introductionmentioning

confidence: 99%

Effects of Cationic Micelles on Rate of Intramolecular General Base-Catalyzed Aminolysis of Ionized Phenyl Salicylate

et al. 1997

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Effects of cetyltrimethylammonium bromide (CTABr) micelles on second-order rate constants (k n obs) for the nucleophilic reactions of amines (n-butylamine, piperidine, and pyrrolidine) with ionized phenyl salicylate (PS-) reveal a decrease of nearly 4-fold for n-butylamine, 13-fold for piperidine, and 17-fold for pyrrolidine with an increase in [CTABr]T from 0.0 to 0.01 M at 35 °C. These results show that the binding constants (K N) of amines with CTABr micelles vary in the order K N for n-butylamine > K N for piperidine > K N for pyrrolidine. The observed data are explained in terms of the pseudophase model of the micelle. The values of K N for n-butylamine, piperidine, and pyrrolidine turn out to be so small that they could not be determined kinetically. The significantly lower rate of aminolysis in the micellar pseudophase compared to that in the aqueous pseudophase is attributed to both micellar medium effect and different locations of amine and PS- in the micellar pseudophase.

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“…The effects of micelles on the rates of intramolecular nucleophilic and general acid-base-catalyzed reactions have been extensively studied. 4 We have studied the effects of anionic micelles on IGB catalysis in the hydrolysis, 5 alkanolysis, 6 and aminolysis 7 of PS -.…”

Section: Introductionmentioning

confidence: 99%

Kinetics and Mechanism of Intramolecular General Base-Catalyzed Methanolysis of Ionized Phenyl Salicylate in the Presence of Cationic Micelles

Khan

Arifin

1996

Langmuir

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The methanolysis of ionized phenyl salicylate, PS -, has been studied in the absence and presence of 0.03 M cetyltrimethylammonium bromide, CTABr, at 0.01 M NaOH and within the CH3OH content range of 10-80 or 90% (v/v). The pseudo-first-order rate constants, kobs, remain unchanged with change in [CTABr]T from 0.0 to 0.03 M at g65% (v/v) CH3OH. The ratio, kobs(0.0 M CTABr)/kobs(0.03 M CTABr) decreases from 4.6 to 1.1 with increase in CH3OH content from 10 to 60% (v/v). At the constant temperature and [CH3OH]T, the rate constants, kobs, show a decrease with increase in [CTABr]T. These results are explained in terms of a pseudophase model of micelle. At 30°C, the pseudo-first-order rate constants, k M MeOH , for the reaction of CH3OH with PS -in the micellar pseudophase and cmc of CTABr increase from 9.63 × 10 -4 and 1.8 × 10 -4 to 78.8 × 10 -4 s -1 and 60.0 × 10 -4 M, respectively, while the binding constants, K1, decrease from 8080 to 39 M -1 with increase in methanol content from 10 to 50% (v/v). Similar results are obtained at different temperatures ranging from 25 to 45°C. The activation parameters, ∆H* and ∆S*, for k M MeOH are larger than those for k NM MeOH (where k NM MeOH represents pseudo-first-order rate constant for the reaction of CH3OH with PS -in the nonmicellar pseudophase) at 10, 20, and 30% (v/v) CH3OH. These results are attributed to the increased ground-state stability of a monomeric methanol in the micellar pseudophase compared to that in the nonmicellar pseudophase. The thermodynamic parameters, ∆H0 and ∆S0, for binding constant, K1, reveal the decrease from -8.6 and -10.5 to -14.1 kcal/mol and -31.9 cal/(K mol), respectively, with increase in CH3OH content from 10 to 30% (v/v). Significantly lower values of k M MeOH compared to those of k NM MeOH at low contents of CH3OH are ascribed to (i) reduced [CH3OH] in the micellar pseudophase, where PS -molecules exist, compared to [CH3OH] in the nonmicellar pseudophase and (ii) partial loss of the efficiency of intramolecular general base catalysis due to probable ion-pair formation between anionic site of micellized PS -molecule and the cationic micellar headgroups.

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Effects of anionic micelles on intramolecular general base-catalysed aminolysis of phenyl and methyl salicylates

Cited by 11 publications

References 4 publications

Reductivity of methanol and ethanol towards permanganate in absence and presence of Tween-20 in perchloric acid medium. Mechanism of the oxidation processes

Reductivity of methanol and ethanol towards permanganate in absence and presence of Tween-20 in perchloric acid medium. Mechanism of the oxidation processes

Effects of Cationic Micelles on Rate of Intramolecular General Base-Catalyzed Aminolysis of Ionized Phenyl Salicylate

Kinetics and Mechanism of Intramolecular General Base-Catalyzed Methanolysis of Ionized Phenyl Salicylate in the Presence of Cationic Micelles

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