A series second-first-order mechanism for the oxidation of primary and secondary alcohols by Cr(VI) reagents

Agarwal, S.; Tiwari, H. P.; Sharma, J. P.

doi:10.1016/s0040-4020(01)89764-7

Cited by 14 publications

(4 citation statements)

References 11 publications

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“…It makes the oxidant lipid soluble, mild, and many a time chemoselective. Tailor-made oniums have been used as the counterions wherein heterocyclic bases such as pyridine, quinoline, caffeine, imidazole, and nicotine 5 units become a part of the oxidant. In different reaction conditions, sometimes these oxidants show biomimetic characteristics due to the counterions providing a micro-heterogeneous environment with different solubilization pockets for the substrates as in the case of micelles, reversed micelles, microemulsions, vesicles for artificial systems, and proteins and lipid membranes in living systems .…”

Section: Introductionmentioning

confidence: 99%

Oxidation of Alcohol by Lipopathic Cr(VI): A Mechanistic Study

Patel

Mishra

2006

J. Org. Chem.

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The oxidation kinetics of various aliphatic primary and secondary alcohols having varied hydrocarbon chain length were studied using cetyltrimethylammonium dichromate (CTADC) in dichloromethane (DCM) in the presence of acetic acid and in the presence of a cationic surfactant. The rate of the reaction is highly sensitive to the change in [CTADC], [alcohol], [acid], [surfactant], polarity of the solvents, and reaction temperature. A Michaelis-Menten type kinetics was observed with respect to substrate. The chemical nature of the intermediate and the reaction mechanism were proposed on the basis of (i) observed rate constant dependencies on the reactants, that is, fractional order with respect to alcohol and acid and a negative order with respect to oxidant, (ii) high negative entropy change, (iii) inverse solvent kinetic isotope effect, k(H2O)/k(D2O) = 0.76, (iv) low primary kinetic isotope effect, kH/kD = 2.81, and (v) the k(obs) dependencies on solvent polarity parameters. The observed experimental data suggested the self-aggregation of CTADC giving rise to a reverse micellar system akin to an enzymatic environment, and the proposed mechanism involves the following: (i) formation of a complex between alcohol and the protonated dichromate in a rapid equilibrium, equilibrium constant K = 5.13 (+/-0.07) dm(3) mol(-1), and (ii) rate determining decomposition (k(2) = (7.6 +/- 0.7) x 10(-3) s(-1)) of the ester intermediate to the corresponding carbonyl compound. The effect of [surfactant] on the rate constant and the correlation of solvent parameters with the rate constants support the contribution of hydrophobic environment to the reaction mechanism.

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Section: Introductionmentioning

confidence: 99%

Oxidation of Alcohol by Lipopathic Cr(VI): A Mechanistic Study

Patel

Mishra

2006

J. Org. Chem.

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“…These reagents have amphipathic cations (mostly quaternary ammonium ions) as the carriers of the anionic oxidant unit to solubilize it in organic solvents. A large number of quaternary nitronium ions, such as pyridinium [1], substituted pyridinium [2], quinolinium [3], imidazolium [4], benzimidazolium [5], caffeinilium [6], nicotinium [7], prolinium [8], piperazinium [9], etc., have been used as carriers for Cr(VI) as its chromate or dichromate into organic media. The reagents are mostly acidic with H as a quaternizing species and are reported to be mild and chemoselective.…”

Section: Introductionmentioning

confidence: 99%

A novel lipopathic Cr(VI) oxidant for organic substrates: Kinetic study of oxidation of benzyl alcohol

Patel¹,

Mishra²

2006

Int J of Chemical Kinetics

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A novel lipopathic oxidizing agent, cetyltrimethylammonium dichromate, was used for oxidation of benzyl alcohol in various organic solvents and in surfactant systems. The reaction kinetics was investigated with change in [acid], [substrate], [oxidant], [surfactant], and temperature. The rate constant values led to propose that the reaction occurs in a reversed micellar system produced by the oxidant, akin to an enzymatic environment. The rate variation with variation in [surfactant] and solvent isotope effect suggest that the path of reaction to be through the formation of an ester complex, the decomposition of which is the rate-determining step.

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“…The oxidants ICC and BCC were prepared and characterized according to reported method 17,18 . All other chemicals used were of AnalaR grade.…”

Section: Methodsmentioning

confidence: 99%

Oxidation of DL - Methionine by Imidazolium Chlorochromate and Benzimidazolium Chlorochromate in Aqueous Perchlorate Medium

2013

Chem Sci Trans

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Abstract:The oxidation of methionine by oxidants such as imidazolium chlorochromate (ICC) and benzimidazolium chlorochromate (BCC) in aqueous perchlorate medium has been studied spectrophotometrically over the range 3.00 ≤ ) for the electron transfer reaction were found to be 12.5 and -154.1 in case of in case of BCC respectively. The product of the reaction was found to be methionine sulphoxide. The negative values of ΔS ≠ support ordered transition state for both the electron transfer reactions due to ICC and BCC.

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A series second-first-order mechanism for the oxidation of primary and secondary alcohols by Cr(VI) reagents

Cited by 14 publications

References 11 publications

Oxidation of Alcohol by Lipopathic Cr(VI): A Mechanistic Study

Oxidation of Alcohol by Lipopathic Cr(VI): A Mechanistic Study

A novel lipopathic Cr(VI) oxidant for organic substrates: Kinetic study of oxidation of benzyl alcohol

Oxidation of DL - Methionine by Imidazolium Chlorochromate and Benzimidazolium Chlorochromate in Aqueous Perchlorate Medium

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