The Chromic Acid Oxidation of Isopropyl Alcohol in 86.5% Acetic Acid Solution. The Chemistry of the Chlorochromate Ion

Cohen, Merrill; Westheimer, F. H.

doi:10.1021/ja01137a044

Cited by 68 publications

(13 citation statements)

References 3 publications

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“…In this work, it was found ( Table 2) that the reaction rate depends on the nature of the mineral acid used as solvent. Therefore, in agreement with other authors (19)(20)(21)(22), it is possible that the protonation of the acid chromate ion will be accompanied by the incorporation of the anion form of the mineral acid used as solvent, which will considerably affect the subsequent oxidant capability of the new species of Cr(VI), according to the following equilibrium:…”

Section: Resultssupporting

confidence: 86%

“…This problem was avoided by a statistical method (19,20), which on the one hand permits a reliable estimation of the isokinetic temperature ( p = 909 K) and on the other hand vouches for the validity of the isokinetic relationship. In this work, it was found ( Table 2) that the reaction rate depends on the nature of the mineral acid used as solvent.…”

Section: Resultsmentioning

confidence: 99%

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Chromic oxidation of lactic acid in very strong acid media

Alvarez-Macho¹,

Montequi-Martin²

1990

Can. J. Chem.

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M A R~A PIEDAD ALVAREZ-MACHO and M A R~A ISABEL MONTEQUI-MARTIN. Can. J. Chern. 68,29 (1990). The oxidation of lactlc acid by chromic acid was studied at high concentrations of HCIO?, HN03, and H2S04 It was observed that the reaction rate depends not only on the acidity of the medium, but also on the nature of the mineral acid. The use of the Bunnett and Bunnett-Olsen criteria and the excess acidity concept allows us to propose a reaction mechanism of the A-2 type, the rate-determining step being a bimolecular process in whlch water participates as a nucleophile. The enthalpy and entropy of activation were determined; the decrease of the magnitude of these parameters when the acidity of the medium was increased I suggests the existence of a compensation effect.

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Section: Resultssupporting

confidence: 86%

Section: Resultsmentioning

confidence: 99%

Chromic oxidation of lactic acid in very strong acid media

Alvarez-Macho¹,

Montequi-Martin²

1990

Can. J. Chem.

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“…Westheimer and coworkers have shown that a primary kinetic isotope effect of approximately 7 : l is observed for the oxidation of 2-propanol-2-d in either aqueous or acetic acid solutions (1,11,12). I n the present investigation the primary ltinetic isotope effect was determined a t 25' for two different concentrations of trifluoroacetic acid.…”

Section: Isotope Effectsmentioning

confidence: 73%

The Chromic Acid Oxidation of 2-Propanol in Trifluoroacetic Acid

Lee¹,

Johnson²

1965

Can. J. Chem.

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The mechanism of the chromic acid oxidation of 2-propanol in trifluoroacetic acid solutions has been studied. The general features of this reaction strongly resemble those observed in aqueous solutions of other strong acids. A "normal" primary kinetic isotope effect is observed, similar thermodynamic parameters are obtained, and the rate behaves in similar way towards changes in acidity.An extensive study of the effect of added salts on this reaction has substantiated that the identity of added anions has a profound effect on the rate of reaction and that any complete reaction mechanism must take this into consideration.I t has been established that chromic acid is a very effective reagent for the oxidation of alcohols and that under similar conditions of acidity and temperature the rate of oxidation is inuch faster in acetic acid solutions than in aqueous solutions (I). T h e kinetics and mechanism of this reaction have been investigated quite thoroughly and it appears that the enhanced rate in acetic acid solutions is due in part to incorporation of an acetate ligand into the chromic acid ester, which acts as an intermediate in this reaction (1,2). I t seemed probable to us that the details of the mechanism of this reaction could be further exposed by undertaking a kinetic study of the chromic acid oxidation of 2-propanol in trifluoroacetic acid solutions. The following paper reports the results of this investigation. EXPERIMENTAL Kinetic nlethodsAll kinetic measurements were made spectrophotometrically using a Unicam model S P 500 spectrophotometer with a thermostated cell compartment. Solutions were made up by adding a weighed amount of anhydrous trifluoroacetic acid (Halocarbon Products) to a dilute aqueous solution of IC2Cr2O7 (Fisher Reagent). This solution was then brought to 25.0 f 0.2" in a thermostated bath and a n excesspf 2-propano1 was added volumetrically either from a pipet or a microsyringe fitted with a Chaney adaptor. The optical density of these solutions a t 3 500 A was then determined a t intervals and a plot of log [CrVI] against time was prepared. A typical rate plot is presented in Fig. 1.

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“…note that chloride ion (9) also effects a marked retardation in the rate of persulphate oxidations, and this may be due t o displacemeilt of Sod= from S z 0 8 = by C1-to give C1OSO3-. This, too, is analogous to the effect of C1-on chromic acid oxidations, due to formation of ClCr0,- (10). In view of these experimental observations it would seem that the "inhibition" of the persulphate oxidation of alcohols by EDTA, reported by Edwards (l),_has no more t o do with the elinli~latio~l of trace metal catalysis t h a i~ the "i~lhibition"~ by ally1 acetate, reported by UTiberg (2), has t o do with removal of S04' or HO.…”

Section: I T Shozrld Be Noted That We Encountered No Dificulty I N mentioning

confidence: 82%