Kinetics and Mechanism of the Autocatalytic Oxidation of L-Asparagine in a Moderately Concentrated Sulfuric Acid Medium

Zahedi, Mansour; Bahrami, Homayoon

doi:10.1023/b:kica.0000032168.35401.3e

Cited by 31 publications

(44 citation statements)

References 9 publications

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“…Also initially, the amino acid and permanganate form a complex, which is hindered by the steric hindrance increase in carbon chain that is accompanied by decreasing of the reaction rate. As such the results presented by the above Taft's analysis fully corroborates the mechanism presented in our previous studies [15,16]. Ignoring L-norleucine data from Figs.…”

Section: The Effect Of Structural Isomerism On Noncatalytic Pathway Usupporting

confidence: 91%

“…Same trends for L-iso-leucine and L-tert-leucine similar to L-norleucine have been observed, so it could be concluded that Mn 2+ is the autocatalytic agent. But in contrast to our previous studies [15,16], for Mn 2+ to show "delayed autocatalytic characteristic," it should acquire a certain concentration, which we call "critical concentration." This critical concentration depends on the nature of amino acid used.…”

Section: Rate Equationcontrasting

confidence: 88%

“…In our previous studies [15,16], we have reported the presence of an autocatalytic effect in which Mn 2+ is an autocatalytic agent. In the present investigation, we have examined oxidation of L-norleucine, L-leucine, L-iso-leucine, and L-tert-leucine in strong acid medium by permanganate.…”

Section: Introductionmentioning

confidence: 88%

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Delayed autocatalytic behavior of Mn(II) ions at a critical ratio: The effect of structural isomerism on permanganic oxidation of L‐norleucine

Bahrami

Zahedi

2005

Int J of Chemical Kinetics

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The kinetics of the permanganic oxidation process of L-norleucine, L-leucine, L-isoleucine, and L-tert-leucine in strong acid medium has been investigated using a spectrophotometric technique. Conclusive evidences have proven autocatalytic activity of Mn(II) for these reactions in strong acid medium analogous to weak acid medium, but in the former, ratio of Mn(II) to amino acid concentration must reach a certain amount for autocatalytic phenomenon to emerge, which we call "critical ratio." This critical ratio depends on the nature of the amino acid employed. Thus considering "delayed autocatalytic behavior" of Mn(II) ions, rate equations satisfying observations for both catalytic and noncatalytic routes have been presented. Kinetic data in a noncatalytic pathway have been fitted to a biparametric equation including inductive, steric, and hyperconjugation correction effects, and it is determined that by shifting the side branch on a carbon chain toward an α-carbon atom (adjacent to amino acid's functional group) and also adding branches to the α-carbon atom, the reaction rate in the noncatalytic pathway decreases. Inductive and steric hindrance factors in amino acid's carbon chain are effective on processes' rate both in catalytic and noncatalytic pathways. C 2005 Wiley Periodicals, Inc. Int

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Section: The Effect Of Structural Isomerism On Noncatalytic Pathway Usupporting

confidence: 91%

Section: Rate Equationcontrasting

confidence: 88%

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Delayed autocatalytic behavior of Mn(II) ions at a critical ratio: The effect of structural isomerism on permanganic oxidation of L‐norleucine

Bahrami

Zahedi

2005

Int J of Chemical Kinetics

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“…Asp has been reported to easily undergo autooxidation in the presence of redox active metals. [23] Mass spectroscopic experiments (ESI) of unbuffered methanol solutions (water solutions gave poor results in ESI experiments) show a clear preference for a [1:1] complex ( Figure S1 in the Supporting Information). However, small amounts of [1:2] Ni 2 + /peptide species were detected.…”

Section: Resultsmentioning

confidence: 99%

Solution Structure of a Functional Biomimetic and Mechanistic Implications for Nickel Superoxide Dismutases

et al. 2008

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The nickel complex of a synthetic nonapeptide (HCDLPCFVY-NH2) is capable of catalytically disproportionating O2(.-) and is thus a functional biomimetic for nickel superoxide dismutases. This represents a simplification as compared to a NiSOD "maquette" that is based on a dodecapeptide that was recently reported [Inorg. Chem. 2006, 45, 2358]. The 3D solution structure reveals that the first six residues form a stable macrocyclic structure with a preformed binding site for Ni(II). Proline 5 exhibits a trans peptide linkage in the biomimetic and a cis conformation in NiSOD enzymes. DFT calculations reveal the source of this preference. Mechanistic consequences for the mode of action (identity of the fifth ligand) are discussed. The SOD activity is compared to enzymatic systems, and selected modifications allowed the biomimetic to be reduced to a functional minimal motif of only six amino acids (ACAAPC-NH2).

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“…), 7.50-7.52 (dd, J = 7.6, 2.4 Hz, 2H, 4,5-CH-arom. A fresh solution of permanganate was prepared and was standardized as reported earlier [31] [32]. All other chemicals were of Aldrich grade.…”

Section: Methodsmentioning

confidence: 99%

A Comparative Kinetic Study on the Efficacious Permanganate Oxidation of Fluorenes in Perchloric and Sulfuric Acid Media

Jassas¹,

Fawzy²,

Obied³

et al. 2017

OJPC

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Oxidation kinetics of fluorene (Fl) and its halogenated derivatives, namely, 2,7-dichlorofluorene (Fl-Cl), 2,7-dibromofluorene (Fl-Br) and 2,7-diiodofluorene (Fl-I), by permanganate ion in both perchloric and sulfuric acid media have been investigated using conventional spectrophotometric technique. In both acidic media, the reactions manifested first order kineticsin [permanganate] and less than unit order each in [reductants] and [acid]. Increasing ionic strength had no effect on the oxidation rates. Oxidation rates of fluorenes in perchloric acid were higher than those in sulfuric acid and the order of the oxidation rates was: Fl > Fl-I > Fl-Br > Fl-Cl. Final oxidation products were identified by GC/MS and FT-IR analyses in all cases as 9H-fluorenone derivatives. Reaction constants as well as activation parameters of the second order rate constants were also evaluated.

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Kinetics and Mechanism of the Autocatalytic Oxidation of L-Asparagine in a Moderately Concentrated Sulfuric Acid Medium

Cited by 31 publications

References 9 publications

Delayed autocatalytic behavior of Mn(II) ions at a critical ratio: The effect of structural isomerism on permanganic oxidation of L‐norleucine

Delayed autocatalytic behavior of Mn(II) ions at a critical ratio: The effect of structural isomerism on permanganic oxidation of L‐norleucine

Solution Structure of a Functional Biomimetic and Mechanistic Implications for Nickel Superoxide Dismutases

A Comparative Kinetic Study on the Efficacious Permanganate Oxidation of Fluorenes in Perchloric and Sulfuric Acid Media

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