Kinetics and Mechanism of Deamination and Decarboxylation of 2-Aminopentanedioic Acid by Quinolinium Dichromate (QDC) in Aqueous Perchloric Acid Medium

Khan, Aftab Aslam Parwaz; Mohd, Ayaz; Bano, Shaista; Siddiqi, K. S.

doi:10.1021/ie100853p

Cited by 14 publications

(8 citation statements)

References 35 publications

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“…= 40 °C− 126.95 J/K/mol. However energy of activation is closer to the value normally found in bimolecular reaction and entropy of activation indicates a more organized transition state[24].…”

supporting

confidence: 62%

Kinetic study of uncatalyzed and Cu(II) catalyzed oxidation of ofloxacin in aqueous alkaline medium and their mechanistic aspects

Tazwar¹,

Devra²

2019

SN Appl. Sci.

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The presence and accumulation of antibacterial drugs in environment, may pose threats to the ecosystem and human health. Hence, oxidation process is of significant to minimize possibility of health risk. The present study aimed to uncatalyzed and Cu(II) catalyzed oxidative degradation of antibacterial drug ofloxacin by hexacyanoferrate(III) in aqueous alkaline medium at 40 °C temperature. The stoichiometry of the reaction indicates that the oxidation of 1 mol of ofloxacin requires 2 mol of hexacyanoferrate(III). The uncatalyzed reaction exhibited first order kinetics with respect to [hexacyanoferrate(III)] and [ofloxacin] and less than unit order with respect to [OH − ]. The catalyzed reaction gives first order kinetics with respect to [hexacyanoferrate(III)] and [OH − ] and less than unit order with respect to [ofloxacin]. The products were also identified on the basis of stoichiometric results and confirm by the characterization results of liquid chromatography mass spectroscopy and Fourier transform infrared analysis. The major product of the reaction obtained by the decarboxylation of the quinolones moiety and hence it may retain the antibacterial activity. Uncatalyzed reaction simultaneously occurs with the Cu(II) catalyzed reaction and the following rate law confirms to all experimental data observed in the reaction: k �� = k un + K 1 K 3 k[Cu(II)][OH − ][OFL] K 2 +K 3 [OFL] , where k ′′ = (k un + k c) is the total observed first order rate constant, k un = Pseudo first order rate constant for uncatalyzed reaction, K c = Pseudo first order rate constant for catalyzed reaction. A reaction mechanism accounting for all these experimental results has been suggested.

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supporting

confidence: 62%

Kinetic study of uncatalyzed and Cu(II) catalyzed oxidation of ofloxacin in aqueous alkaline medium and their mechanistic aspects

Tazwar¹,

Devra²

2019

SN Appl. Sci.

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“…The high-negative values of ΔS ‡ are indicative of involvement of a highly ordered transition state rather than the reactants. 63,64 It supports the existence of a cyclic or a forced transition state during the abstraction of the ohydroxyl proton of complex C2 to form adrenochrome in the rate-determining step. 65 The proposed mechanism especially formation of forced nonpolar transition state is further supported by the effect of solvent polarity on the reaction rate.…”

Section: ■ Results and Discussionmentioning

confidence: 77%

Oxidation of Epinephrine to Adrenochrome by Cetyltrimethylammonium Dichromate: A Mechanistic Study

Garnayak

Patel

2014

Ind. Eng. Chem. Res.

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The present study reports the oxidation of epinephrine (adrenaline), a neurotransmitter by a lipid compatible lipophilic Cr (VI) oxidant, cetyltrimethylammonium dichromate (CTADC). The kinetics of the reaction is studied in organic media in the presence of acetic acid by UV–vis spectroscopic method. The rate of the reaction is measured by monitoring adrenochrome, the oxidized product of epinephrine at 455 nm. The reaction is fractional order with respect to CTADC and epinephrine. Acetic acid is found to retard the rate of the reaction. A suitable ionic mechanism is proposed based on the experimental findings where epinephrine is converted to adrenochrome through the intermediate, leucochrome. The proposed reaction mechanism is also supported by the effect of solvent, effect of temperature, and effect of surfactants on the rate of the reaction. The decrease in rate constant due to increase in polarity and hydrogen bond acceptor ability of the solvent indicates the existence of a less polar transition state and stabilization of the reactants through strong intermolecular hydrogen bonding. The addition of surfactants (cationic, anionic, and nonionic) decreased the rate of reaction, and the retardation is explained through the partition of oxidant and substrate in different microheterogeneous media.

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“…The solvent isotope effect k (H 2 O)/ k (D 2 O) was found to be ((3.3 × 10 −3 )/(4.84 × 10 −3 )) = 0.68. The acid‐catalyzed rate is faster in D 2 O than in H 2 O, when a preequilibrium protonation is involved . The inverse solvent kinetic isotope effect, i.e., k (D 2 O) > k (H 2 O), indicates that the NH 2 group is not involved in the rate‐determining step and thus supports the formation of complex “C” in the reaction process.…”

Section: Resultsmentioning

confidence: 99%

Oxidation of Antitubercular Drug Isoniazid by a Lipopathic Oxidant, Cetyltrimethylammonium Dichromate: A Mechanistic Study

Garnayak

Patel

2015

Int. J. Chem. Kinet.

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The oxidation of an antitubercular drug isoniazid by a lipopathic oxidant cetyltrimethylammonium dichromate (CTADC) in a nonpolar medium generates isonicotinic acid both in the presence and the absence of acetic acid. The conventional UV–vis spectrophotometric method is used to study the reaction kinetics. The occurrence of the Michaelis–Menten–type kinetics with respect to isoniazid confirms the binding of oxidant and substrate to form a complex before the rate‐determining step. The existence of the inverse solvent kinetic isotope effect, k(H2O)/ k(D2O) = 0.7, in an acid‐catalyzed reaction proposes a multistep reaction mechanism. A decrease in the rate constant with an increase in [CTADC] reveals the formation of reverse micellar–type aggregates of CTADC in nonpolar solvents. In the presence of different ionic and nonionic surfactants, CTADC forms mixed aggregates and controls the reaction due to the charge on the interface and also due to partition of oxidant and substrate in two different domains. High negative entropy of activation (ΔS‡ = –145 and –159 J K−1 mol−1 in the absence and presence of acetic acid) proposes a more ordered and highly solvated transition state than the reactants. Furthermore, the solvent polarity‐reactivity relationship reveals (i) the presence of less polar and less ionic transition state compared to the reactants during the oxidation, (ii) differential contribution from nonpolar and dipolar aprotic solvents toward the reaction process, and (iii) the existence of polarity/hydrophobic switch at log P = 0.73. A suitable mechanism has been proposed on the basis of experimental results. These results may provide insight into the mechanism of isoniazid oxidation in hydrophobic environment and may assist in understanding the drug resistance in different location.

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Kinetics and Mechanism of Deamination and Decarboxylation of 2-Aminopentanedioic Acid by Quinolinium Dichromate (QDC) in Aqueous Perchloric Acid Medium

Cited by 14 publications

References 35 publications

Kinetic study of uncatalyzed and Cu(II) catalyzed oxidation of ofloxacin in aqueous alkaline medium and their mechanistic aspects

Kinetic study of uncatalyzed and Cu(II) catalyzed oxidation of ofloxacin in aqueous alkaline medium and their mechanistic aspects

Oxidation of Epinephrine to Adrenochrome by Cetyltrimethylammonium Dichromate: A Mechanistic Study

Oxidation of Antitubercular Drug Isoniazid by a Lipopathic Oxidant, Cetyltrimethylammonium Dichromate: A Mechanistic Study

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