Micellar effect on the reaction of picolinic acid catalyzed chromium(VI) oxidation of dimethyl sulfoxide in aqueous acidic media: A kinetic study

Das, Asim K.; Mondal, Sudhin K.; Kar, Dalia; Das, Madhusweta

doi:10.1002/1097-4601(200103)33:3<173::aid-kin1011>3.0.co;2-i

Cited by 28 publications

(16 citation statements)

References 28 publications

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“…However, it is observed that in the lower regions of [Cr(VI)], the pseudo-first order rate constant increases with decrease in [Cr(VI)] ( Table 1). Such type of decrease in rate with increase in [Cr(VI)] has been observed by several researchers [33][34][35][36]. However, the rate constants remain constant at higher concentration range of Cr(VI).…”

Section: Resultsmentioning

confidence: 51%

“…However, the rate constants remain constant at higher concentration range of Cr(VI). The decrease in rate with increase in Cr(VI) in lower concentration region may be due to the dimerization of Cr(VI) followed by decrease in concentration of active species [33][34][35] or due to the existence of some sort of weak association between monomeric Cr(VI) species [36]. The reaction is first order each in PSAA and oxalic acid, which are evidenced from the constant values obtained by dividing k 1 Table T1) and shows a first order dependence with respect to [H + ].…”

Section: Resultsmentioning

confidence: 99%

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Spectral Evidence for the One-Step Three-Electron Oxidation of Phenylsufinylacetic Acid and Oxalic Acid by Cr(VI)

Subramaniam¹,

Selvi²

2013

AJAC

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The co-oxidation of a mixture of phenylsulfinylacetic acid (PSAA) and oxalic acid (OxH 2 ) by Cr(VI) in 20% acetonitrile-80% water (v/v) medium follows third order kinetics, first order, each with respect to PSAA, OxH 2 and Cr(VI). The reaction involves nucleophilic attack of sulfur atom of PSAA on chromium of the oxidizing species, Cr(VI)-OxH 2 to form a ternary complex, Cr(VI)-OxH 2 -PSAA followed by a one-step three-electron reduction of Cr(VI) to Cr(III) and simultaneous oxidation of both the substrates. The reaction is catalysed by Mn 2+ ion while retarded by Al 3+ ion. Electron releasing substituents in the meta-and para-positions of the phenyl ring of PSAA enhance the rate of co-oxidation while electron withdrawing substituents retards the reaction. The Hammett plots at different temperatures exhibit excellent correlation with negative ρ values. The reaction series obey isokinetic relationship and the observed isokinetic temperature is lying below the experimental range of temperature.

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Section: Resultsmentioning

confidence: 51%

Section: Resultsmentioning

confidence: 99%

Spectral Evidence for the One-Step Three-Electron Oxidation of Phenylsufinylacetic Acid and Oxalic Acid by Cr(VI)

Subramaniam¹,

Selvi²

2013

AJAC

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“…The UV-visible spectra of Cr(III) ion shows two peaks at 421 nm and 592 nm which are attributed to the octahedral transitions, 4 A 2g (F) → 4 T 1g (F) and 4 A 2g (F) → 4 T 2g (F) [36][37][38] whereas the spectrum of the product mixture exhibits two peaks at 408 nm and 542 nm ( Figure 4). This clearly demonstrates that Cr(VI) is reduced to Cr(III) ion but the blue shift observed in λ max values for the product mixture is due to existence of Cr(III) in the form of complex, probably the Cr(III)-PA complex as reported in the PA catalysed Cr(VI) oxidation reactions [12][13][14]. …”

Section: Product Analysismentioning

confidence: 55%

“…Thus, the active species in this reaction is Cr(VI) itself, which exists in aqueous acidic solution in a variety of forms such as CrO 4 [12,14,49] it has been observed that the redox potential of Cr(VI) increases in the presence of chelating agents and believed that Cr(VI) forms complexes with the chelating agents. Thus in the present case, the increase in reaction rate with increase in [PA] may be attributed to the formation of a bimolecular cyclic complex (C 1 , Scheme 1) between Cr(VI) and PA which is assumed to be the kinetically active oxidizing species [12,[17][18][19]. The spectral evidence for the formation of Cr(VI)-PA complex is obtained from the hyperchromic shift and broadening of the UV absorption peak at 263 nm after the addition of PA to Cr(VI) (Figure 6).…”

Section: Discussionmentioning

confidence: 99%

“…Thus PA is not a true catalyst and it is better described as a promoter. Picolinic acid promoted Cr(VI) oxidation of several organic substrates [12][13][14][15][16] including organic sulfur compounds [12,[17][18][19] have been extensively studied. The catalytic effect was attributed to the activation of oxidizing species of chromium through a precursor complex formation.…”

Section: Introductionmentioning

confidence: 99%

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Picolinic acid promoted oxidative decarboxylation of phenylsulfinylacetic acid by Cr(VI)

Subramaniam¹,

Selvi²

2016

Bull. Chem. Soc. Eth.

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ABSTRACT. The kinetics and mechanism of picolinic acid promoted reaction of phenylsulfinylacetic acid (PSAA) with Cr(VI) was carried out in aqueous acetonitrile medium under pseudo first order conditions. The reaction follows Michaelis-Menten type of kinetics with respect to PSAA. The catalytic activity by picolinic acid can be interpreted on the basis of the formation of a highly active oxidizing species, Cr(VI)-PA complex. The mechanism involves the formation of a termolecular complex, Cr(VI)-PA-PSAA by the nucleophilic attack of the sulfur atom of PSAA on chromium of Cr(VI)-PA complex in an equilibrium step followed by ligand coupling in a slow step. Electron releasing substituents in the phenyl ring of PSAA accelerate while electron withdrawing groups retard the reaction rate. The overall rate constants for the para-and meta-substituted PSAAs are found to correlate excellently with Hammett σ constants with a very low reaction constant, ρ. .

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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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Micellar effect on the reaction of picolinic acid catalyzed chromium(VI) oxidation of dimethyl sulfoxide in aqueous acidic media: A kinetic study

Cited by 28 publications

References 28 publications

Spectral Evidence for the One-Step Three-Electron Oxidation of Phenylsufinylacetic Acid and Oxalic Acid by Cr(VI)

Spectral Evidence for the One-Step Three-Electron Oxidation of Phenylsufinylacetic Acid and Oxalic Acid by Cr(VI)

Picolinic acid promoted oxidative decarboxylation of phenylsulfinylacetic acid by Cr(VI)

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

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