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Kinetics and Mechanistic Study of Permanganate Oxidation of L-Citrulline in Acidic and Basic Media
Ismail I. Althagafi,
Ahmed Fawzy
Issue:
Volume 5, Issue 6, December 2016
Pages:
99-107
Received:
29 August 2016
Accepted:
17 October 2016
Published:
29 November 2016
Abstract: Kinetics of oxidation of L-citrulline (Cit) by permanganate ion in both acidic and basic media has been investigated spectrophtometrically at constant ionic strengths and at 25°C. In both media the reactions exhibited first order dependence in [permanganate] and less than unit order dependences in L-citrulline concentration. A fractional-second order dependence with respect to [H +] and a fractional-first order dependence with respect to [OH-] were revealed in acidic and basic media, respectively. Increasing ionic strength in basic medium increased the oxidation rate of L-citrulline, whereas it had a negligible effect on the oxidation rate in acidic medium. The rate-determining step in both media is suggested to involve a one-electron change, but the stoichiometry (L-citrulline: permanganate) was different, being 5:2 in acidic medium and 1:2 in basic medium. The proposed oxidation mechanisms involve formation of 1:1 intermediate complexes between kinetically active species of both L-citrulline and permanganate ion in pre-equilibrium steps. The final oxidation products of L-citrulline were identified in both acidic and basic media as the corresponding aldehyde (4-(carbamoylamino) butyraldehyde), ammonia and carbon dioxide. The appropriate rate laws are deduced.
Abstract: Kinetics of oxidation of L-citrulline (Cit) by permanganate ion in both acidic and basic media has been investigated spectrophtometrically at constant ionic strengths and at 25°C. In both media the reactions exhibited first order dependence in [permanganate] and less than unit order dependences in L-citrulline concentration. A fractional-second ord...
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Kinetics and Mechanisms of Permanganate Oxidations of Cadaverine in Different Media
Ahmed Fawzy,
Ishaq A. Zaafarany,
Metwally Abdallah,
Rabab S. Jassas,
Rami J. Obaid
Issue:
Volume 5, Issue 6, December 2016
Pages:
108-117
Received:
16 November 2016
Accepted:
23 November 2016
Published:
23 December 2016
Abstract: The kinetics of oxidation of cadaverine (CAD) by permanganate ion in acidic, neutral and alkaline media has been investigated spectrophtometrically at constant ionic strengths and temperature. The reactions in different media exhibited a first order kinetics in [MnO4-] and less than unit order dependences with respect to [CAD]. The oxidation of cadaverine showed less than unit order dependences with respect to [H+] and [OH-] in acidic and alkaline media, respectively. Variation of ionic strengths in both acidic and alkaline media had no significant effect on the oxidation rates. The proposed oxidations mechanisms in all media involve formation of 1:1 intermediate complexes between the kinetically active species of both cadaverine and permanganate ion. The final oxidation products of cadaverine were identified as 5-aminopentanal and ammonia. The appropriate rate laws in all media were deduced. The reaction constants involved in the different steps of the mechanisms were evaluated.
Abstract: The kinetics of oxidation of cadaverine (CAD) by permanganate ion in acidic, neutral and alkaline media has been investigated spectrophtometrically at constant ionic strengths and temperature. The reactions in different media exhibited a first order kinetics in [MnO4-] and less than unit order dependences with respect to [CAD]. The oxidation of cad...
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Solvent Effects on the Kinetics of the Dakin-West Reaction
Issue:
Volume 5, Issue 6, December 2016
Pages:
118-127
Received:
21 November 2016
Accepted:
5 December 2016
Published:
12 January 2017
Abstract: The rate of the Dakin-West reaction have been investigated in Me2SO, THF and CH3CN at the temperature range (55–70) are reported. First order rate constants were obtained in each case. A Bronsted slope was found to be equal -0.0277 indicates that the transition state is very reactant-like and the proton has barely moved. Further, the solvent effect was considered from two points of mechanistic view: the thermodynamic transfer function of Me2SO to CH3CN and THF where the rate was found to be fast in Me2SO and slow in THF and CH3CN and the Kirkwood-Buff preferential solvation with aqueous Me2SO, CH3CN and THF. The techniques supported the proposed transition state structure.
Abstract: The rate of the Dakin-West reaction have been investigated in Me2SO, THF and CH3CN at the temperature range (55–70) are reported. First order rate constants were obtained in each case. A Bronsted slope was found to be equal -0.0277 indicates that the transition state is very reactant-like and the proton has barely moved. Further, the solvent effect...
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Adsorption and Kinetic Optimization Study of Acetic Acid from Aqueous Solutions Using Activated Carbon Developed from Vernonia amygdalina Wood
Yilkal Dessie Sintayehu,
Lalisa Terefe Lencha
Issue:
Volume 5, Issue 6, December 2016
Pages:
128-132
Received:
7 December 2016
Accepted:
23 December 2016
Published:
18 January 2017
Abstract: In this study, the adsorption of Acetic acid from an aqueous solution is investigated using activated charcoal prepared from Bitter leaf (Vernoniaamygdalina) that is activated by tap water. Carbonizations at different activation temperature with constant flow of air are used to examine for accepted accessibility of sorbent material. The optimum conditions obtained from this batch adsorption experiments highest adsorption capacity is recorded at activation temperature=400°C, contact time=60 min, pH=6, temperature=25 ± 2°C, charcoal (adsorbent) dosage=0.04 g, acid concentration=0.097 mol/L. More than 85 percent adsorption of acetic acid was recorded in every batch laboratory experiments. Adsorption kinetic and its equilibrium behaviors are studied. It indicates that the adsorption process obeys Pseudo-second-order kinetic and Langmuir isotherm models. The characteristic results and dimensionless separation factor (RL) showed that Bitter leaf wood can be employed as an alternative bio-sorbent in the removal of carboxylic acid from an aqueous solution. The adsorption of acetic acid by Bitter leaf fit well into pseudo second order rate equation and the adsorption also obeyed Langmuir isotherm with a separation factor (RL=0.89). Fourier transforms infrared (FT-IR) analysis treated by tap water indicating good chemical transformations would have taken place.
Abstract: In this study, the adsorption of Acetic acid from an aqueous solution is investigated using activated charcoal prepared from Bitter leaf (Vernoniaamygdalina) that is activated by tap water. Carbonizations at different activation temperature with constant flow of air are used to examine for accepted accessibility of sorbent material. The optimum con...
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