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Plot of 1/D against logkobs showing the effect of solvent polarity for the oxidation of thio acids by TriPAFC.
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![Table 3 Effect of [MnSO 4 ] on the oxidation of thio acids by](publication/271574447/figure/tbl2/AS:667910125137925@1536253591184/Effect-of-MnSO-4-on-the-oxidation-of-thio-acids-by_Q320.jpg)
Kinetics and mechanism of oxidation of thioglycolic acid (TGA). Thiolactic acid (TLA) and thiomalic acid (TMA) by tripropylammonium fluorochromate (TriPAFC) have been studied in N, N-dimethyl formamide (DMF). The reaction is first order with respect to TriPAFC and thioacids (TA). p-Toluene sulfonic acid (TsOH) is used as a source of hydrogen ions....
Citations
... 1,2 Due to lysine and other amino acids' functional role, the oxidation kinetics, with different metal ion oxidants, are of special interest and have undergone extensive investigation. [3][4][5][6] One of the metal ion oxidants of interest is the permanganate heptavalent ion. It is a powerful oxidizing agent and has been used extensively in the oxidation of organic substrates. ...
Kinetics of oxidation of L-lysine by permanganate ion in a perchloric acid medium was investigated to explore the order of the reaction with respect to oxidant and substrate and to study the catalytic behaviour of sodium lauryl sulphate (SLS) and polyethylene glycol (PEG). The reaction was found to be first-order with respect to the oxidant and the substrate and zero-order with respect to hydrogen ion. Changes in the sodium sulphate concentration produce a non-significant variation in the rate of the reaction. SLS and PEG were found to catalyze the reaction. Surfactant catalysis was modelled by Piszkiewicz's cooperativity model, while polymer catalysis was explained with the help of the Benesi-Hildebrand equation. The temperature dependence of the rate of the reaction was elucidated, and activation parameters were obtained. Interestingly, the reaction was found to possess positive activation entropy indicating the dissociative nature of the transition state and outer-sphere electron transfer mechanism. A mechanism of the reaction that is supported by the experimental findings was suggested. Keywords: L-lysine, permanganate ion, micellar catalysis, polymer catalysis, outer sphere electron transfer mechanism.
... As a part of our continuing investigations on the oxidation of organic substrates by Cr(VI) [23][24][25][26][27][28][29], this paper reports the kinetic features of the oxidation of mandelic acids by TriPAFC in aqueous acetic acid medium. The objective of the present work includes a systematic study of the substituent and solvent effects on oxidation of a series of para-substituted mandelic acids, in the varying percentage of acetic acid-water, and the analysis of the data using linear free energy relationships with an aim to get better insight into the mechanism of mandelic acid oxidation. ...
The oxidation of Mandelic Acids (MA) to the corresponding oxoacids with tripropylammonium fluorochromate (TriPAFC) in aqueous acetic acid has been studied. The reaction is first order with respect to [TriPAFC], [MA] and [H ⁺ ]. The oxidation of a-deuteriomandelic acid shows the presence of a primary kinetic isotope effect (k H /k D = 5.54 at 303 K). The reaction has been found to be catalyzed by H + ions. The various thermodynamic parameters for the oxidation have been reported and discussed along with the validity of the isokinetic relationship. The Exner plot showed that all the selected mandelic acids are oxidized by the same mechanism. © 2018, Iranian Institute of Research and Development in Chemical Industries. All rights reserved.
In a non-aqueous medium, oxidation kinetics of thioglycolic, thiolactic and thiomalic acids by benzimidazolium dichromate have been studied. In the temperature range of 20 °C–50 °C, oxidation kinetics were examined by spectrophotometry. In terms of oxidant, the reaction is dependent on the unitary order. In the case of thioacids, we find the Michaelis-Menten kinetics. Hydrogen-ions act as catalyst in this process. The reaction rate slows down as the Mn²⁺ ion concentration increases. The reaction does not cause acrylonitrile to polymerize. The formation of a thioester into the pre-equilibrium followed by its progressive degradation was postulated as a mechanism.
Kinetic study of cholesterol oxidation has been studied using a series of N-cetylpicolinium dichromates (CPDC), a class of phase transfer oxidants, in acetic acid medium under first order conditions with respect to oxidant. Rate constants were calculated in the temperature range 290–300 K. The kinetics was followed spectrophotometrically; cholest-5-en-3-one is found to be the only oxidation product. Unlike the previously reported lipopathic oxidant containing cetyltrimethylammonium ions, these oxidants show a direct variation of rate with the oxidant concentration ruling out any reversed micellar organization of the oxidant molecules. From the experimental data formation of an unstable cyclic transition state followed by intra-molecular proton transfer has been proposed. Solvent isotope effect for the cholesterol oxidation (\({{{{k}_{{{\text{CHC}}{{{\text{l}}}_{3}}}}}} \mathord{\left/ {\vphantom {{{{k}_{{{\text{CHC}}{{{\text{l}}}_{3}}}}}} {{{k}_{{{\text{CDCC}}{{{\text{l}}}_{3}}}}}}}} \right. \kern-0em} {{{k}_{{{\text{CDCC}}{{{\text{l}}}_{3}}}}}}}\) = 1.52) indicated a carbon-hydrogen cleavage rather than a carbon-carbon cleavage. Variation of solvent polarity is found to impose a remarkable impact on the rate of oxidation: more polar reaction environment favours the oxidation by β-CPDC oxidant to a higher extent, compared to the other two oxidant isomers, α-CPDC and γ-CPDC.
It is first reported herein that cobalt(II) complexes solution of monothiol-containing multidentate ligands are used to remove low concentration of nitric oxide (NO). These chelating ligands are water-soluble amines, alcohols or acids which containing at least one -SH group, include those of cysteine, mercaptosuccinic acid, mercaptoethanesulfonate, mercaptopropionic acid and the like. These -SH compounds when coordinated with cobalt ions, forming complexes are very effective for NO removal. The results indicate that the side group (methyl, carboxyl, carboxymethyl) on α-carbon atom of ligands contribute to the denitration of the chelate solution, whereas the substituents on sulfur atom of ligands deactivate the complexation system. In addition, we have found that several monothiol compounds with simple molecule structure and low cost exhibit good performance in denitration, and some of cobalt thiol complexes are more valuable in removing NO than ferrous thiol complexes.
Oxidation kinetics of benzaldehyde and some of its ortho‐ and para‐monosubstituted derivatives have been studied using cetylpicolinium dichromates, a class of novel phase transfer oxidants, in dichloromethane medium. The rate of reaction is first order with respect to oxidant and fractional order with respect to the substrates. The Michaelis–Menten type oxidation was observed with respect to the substrates. Benzaldehydes are found to be oxidized to their corresponding acids. The mechanism of oxidation reaction has been suggested based on the solvent isotope effect, Hammett plot, and thermodynamic study. The solvent isotope effect (kCHCl3/kCDCl3 = 1.57) indicates the involvement of hydrogen exchange with the medium during oxidation reactions. A strong influence of specific solute–solvent interactions on the rate of the reaction is observed. Both the electron‐withdrawing and electron‐releasing substituents on the substrates accelerate the rate of reaction.
A benzalkonium chloride (BKC) catalyzed oxidation of pentaammine cobalt(III) complexes of both bound and unbound α-hydroxy acids by tributylammonium chlorochromate (TriBACC) has been studied. Perchloric acid is adapted as a medium and the oxidative kinetics was contrived spectrophotometrically at room temperature. Rate of TriBACC oxidation is carried out at pseudo-first order conditions and rate constant was calculated. Absence of salt effect is observed on increasing NaClO4 concentration. Abatement in UV-visible absorbance at 503 nm for Co(III) complex confirms to nearly 100 % of initial absorbance. The complex [(NH3)5Co(III)-L]²⁺ shows inner sphere mechanism and induced electron transfer reaction yields 100 % Co(II). The product formed in this oxidation was analyzed and polymerization test was carried out. Comparative study of rate of TriBACC oxidation in presence of benzalkonium chloride is listed out.
The kinetics of oxidation of 4-oxo-4-phenyl butanoic acid (4-oxo acid), p-methoxy (p-OCH3), p-ethoxy (p-OC2H5), p-methyl (p-CH3), p-chloro (p-Cl), p-bromo (p-Br) and p-acetyl (p-COCH3) 4-oxo acids by tripropylammonium fluorochromate (TriPAFC) in aqueous acetic acid medium in the presence of perchloric acid have been described. The reaction is first order with respect to 4-oxo acid, TriPAFC and perchloric acid. The order of reactivity among the studied 4-oxoacids is: p-OCH3 > p-OC2H5 > p-CH3 > p-H > p-Cl > p-Br > p-COCH3. The effect of changes on the electronic nature of the substrate reveals that there is a development of positive charge in the transition state. The activation parameters have been computed from Arrhenius and Eyring plots. Based on the kinetic results, a suitable mechanism has been proposed.
