Kinetics and mechanism of oxidation of malonic acid by chromium(VI) in aqueous perchlorate medium

Rao, Indu; Mishra, S. K.; Sharma, P. D.

doi:10.1007/bf02910730

Cited by 7 publications

(5 citation statements)

References 24 publications

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“…It is due to the rate inhibiting power of sulfate. [8][9][10] It is argued that due to the formation of less efficient oxidizing species, HOCrO 2 OSO 3 H, in the interaction of HSO 4 with Cr(VI) in acidic media, the rate retarding effect arises. [8][9][10] Effect of Surfactants CPC inhibits the reaction both in the presence and absence of PA while SDS catalyses the reaction under compara-ble conditions (cf.…”

Section: Effect Of Mediummentioning

confidence: 99%

Micellar Effect on the Reaction of Chromium(VI) Oxidation of L‐Sorbose in the Presence and Absence of Picolinic Acid in Aqueous Acid Media: A Kinetic Study

Saha

Das

Mohanty

et al. 2004

J Chinese Chemical Soc

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The kinetics and mechanism of chromic acid oxidation of L-sorbose in the presence and absence of picolinic acid (PA) have been studied under the conditions, [L-sorbose]T >> [PA]T >> [Cr(VI)]T, at different temperatures. In the absence of PA, the monomeric chromic acid undergoes esterification with the substrate followed by the acid catalysed redox decomposition of the Cr(VI)-substrate ester through glycol splitting to formaldehyde and the lactone of C5-aldonic acid and Cr(IV) which subsequently participates in the faster reactions. In the presence of PA, the Cr(VI)-PA complex produced in a pre-equilibrium step experiences a nucleophilic attack by the substrate to produce a ternary complex which decomposes through glycol splitting giving rise to the organic products and Cr ( . In the presence of the surfactants like N-cetylpyridinium chloride (CPC, a cationic surfactant) and sodium dodecyl sulfate (SDS, an anionic sulfate), the reaction orders remain unchanged. CPC has been found to inhibit both the uncatalysed and PA-catalysed paths while SDS shows the rate accelerating effect for both the uncatalysed and PA-catalysed paths. The observed micellar effects have been rationalised by considering the distribution of the reactants between the micellar and aqueous phases in terms of the proposed reaction mechanism.

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Section: Effect Of Mediummentioning

confidence: 99%

Micellar Effect on the Reaction of Chromium(VI) Oxidation of L‐Sorbose in the Presence and Absence of Picolinic Acid in Aqueous Acid Media: A Kinetic Study

Saha

Das

Mohanty

et al. 2004

J Chinese Chemical Soc

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“…A similar reaction mechanism is known for the reaction with the 1e-reductants of transition metal ions [41] and [Fe(phen) 3 ] 2+ [107]. In some other cases, this mechanism has also been suggested [82,97,[108][109][110][111]. In the oxidation of alkyl/aryl and diphenyl sulfides by Cr(VI), to explain the excellent correlations obtained between the log k values and the oxidation potentials/ionization energies of the sulfides and the absence of any rate retardation in the presence of Mn(II), the one-electron transfer mechanism (i.e.…”

Section: The Common Pathways Leading To Reduction Of Chromium(vi) To mentioning

confidence: 77%

“…Under the present experimental conditions, concentrations of the higher oligomers are negligibly small. The protonation equilibrium, HCrO − 4 + H + H 2 CrO 4 , is highly favored to the left side (protonation constant ≈ 0.2 [111]). In the micellar media, to facilitate the binding of Cr(VI) species on the micellar surface, formation of H 2 CrO 4 is favored through the protonation of HCrO 4 − [114,127,128].…”

Section: Oxidation Of Alcoholsmentioning

confidence: 99%

Micellar effect on the kinetics and mechanism of chromium(VI) oxidation of organic substrates

Das

2004

Coordination Chemistry Reviews

117

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“…However, the catalytic efficiency measured by keff (={fcobs(T)-^obs(u)l/Us(u)) is approximately unity in aqueous HCIO4 media, while it is relatively higher in aqueous H2S04 media. It is probably due to the inhibiting effect [13] of SO^~ which affects the uncatalysed path more than the ΡΑ-catalysed path (cf. Table III).…”

Section: Fcobs(c) = Fcc[hc02h]t[pa]t[hmentioning

confidence: 99%

Kinetics and Mechanism of the Chromium(VI) Oxidation of Formic Acid in the Presence of Picolinic Acid and in the Presence and Absence of Surfactants

Das¹

1999

BioInorganic Reaction Mechanisms

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The kinetics and mechanism of picolinic acid (PA)-catalysed oxidation of formic acid have been studied in aqueous HCIO4 media under the experimental conditions, 10 3 [Cr(VI)]T = 0.67-2.67 mol dm" 3 , [PA]T = 0.01-0.12 mol dm" 3 ,[HC02H]T = 0.1-0.8 mol dm" 3 , [H + ] = 0.35-1.5 mol dm" 3 ,1 = 1.5 mol dm" 3 in the temperature range 25-40° C. The kinetic parameters of the catalysed path have been compared with those of the relatively slower uncatalysed path which proceed parallelly with the catalysed path. In the catalysed path, Cr(VI)-PA cyclic complex formed at the pre-equilibrium step receives a nucleophilic attack at the Cr(VI) centre by the substrate leading to a ternary complex with the release of a proton in a reversible path. Then the ternary complex experiences the redox decomposition at the rate-determining step giving rise to Cr(IV)-PA complex and C02. Then the Cr(IV)-PA complex reacts faster ultimately giving rise to Cr(III)-PA complex. The anionic surfactant sodium dodecyl sulfate (SDS) catalyses both the uncatalysed and catalysed paths in aqueous HC104 media while the cationic surfactant cetyl pyridinium chloride (CPC) inhibits the reactions in aqueous H2S04 media. In the presence of the surfactants, applicability of the Piszkiewicz model has been tested for the ΡΑ-catalysed path. Micellar effects are in conformity with the proposed mechanism.

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Kinetics and mechanism of oxidation of malonic acid by chromium(VI) in aqueous perchlorate medium

Cited by 7 publications

References 24 publications

Micellar Effect on the Reaction of Chromium(VI) Oxidation of L‐Sorbose in the Presence and Absence of Picolinic Acid in Aqueous Acid Media: A Kinetic Study

Micellar Effect on the Reaction of Chromium(VI) Oxidation of L‐Sorbose in the Presence and Absence of Picolinic Acid in Aqueous Acid Media: A Kinetic Study

Micellar effect on the kinetics and mechanism of chromium(VI) oxidation of organic substrates

Kinetics and Mechanism of the Chromium(VI) Oxidation of Formic Acid in the Presence of Picolinic Acid and in the Presence and Absence of Surfactants

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