13C N.M.R. Spectroscopic Studies on the Reactions of Vanadium(V) With 13C2-Labeled Oxalate in Aqueous and 50% v/v Aqueous Acetic Acid Solutions

1995 ◽  
Vol 48 (4) ◽  
pp. 763 ◽  
Author(s):  
RP Farrell ◽  
PA Lay
Keyword(s):  
Acetic Acid ◽  
Spectroscopic Studies ◽  
Aqueous System ◽  
Aqueous Acetic Acid ◽  
Acid Solutions ◽  
Acetic Acid Medium ◽  
Acid Media ◽  
Coupling Pattern ◽  
Species Being ◽  
Second Peak

13 C n.m.r, spectroscopy has been used to study the reactions of vanadate , H2VO4-, with 13C2-labelled oxalate in aqueous and 50% v/v aqueous acetic acid media. The results of the aqueous system corroborate the natural abundance oxalate 13C n.m.r. studies of Ehde and coworkers ( Ehde, P.M., Petterson , L., and Glaser, J., Acta Chem. Scand., 1991, 45, 998) who report the formation of both mono( oxalato )-, [VO2(ox)(OH2)] - , and bis(oxalato)-vanadium(V), cis-[VO2(ox)2]3-, complexes in solution. At 270 K, pH 3.3, and an n.m.r. operating frequency of 100.16 MHz, the former complex appears as a singlet (167.3 ppm ), while the latter resolves into an AB coupling pattern (169.6, 168.8, 166.6, 165.8 ppm ; Jc -c 85 Hz) owing to the inequivalence of carbons trans and cis to the oxo ligands . In 50% v/v aqueous acetic acid both the mono( oxalato ) singlet (166.8 ppm ) and the bis ( oxalato ) AB coupling pattern (169.2, 168.5, 166.2, 165.5 ppm ; Jc -c ≈ 75 Hz) are present but are somewhat broadened and shifted downfield, which is indicative of other species being present. There is also some resolution of new peaks within the broadened signals. These are believed to be due to the presence of the additional complexes, mainly [VO2(ox)( OAc )]2- and cis-[VO2(ox)( OAc )2]3-, generated in the acetic acid medium. At 298 K, the bis(oxalato) complex exhibits a single 13C peak for the inequivalent carbons at 167.6 ppm because of fluxional behaviour. The mono( oxalato ) complex is in rapid equilibrium with free oxalate, giving a second peak at lower value of 165.7 ppm that is pH-dependent. The mechanisms of the fluxionality of the different complexes are discussed.

scholarly journals Perborate Oxidation of Substituted 5-Oxoacids in Aqueous Acetic Acid Medium: A Kinetic and Mechanistic Study

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
S. Shree Devi ◽  
B. Muthukumaran ◽  
P. Krishnamoorthy
Keyword(s):  
Acetic Acid ◽  
Acid Medium ◽  
Reaction Rate ◽  
Reaction Medium ◽  
Activation Parameters ◽  
Reaction Rates ◽  
Mechanistic Study ◽  
Aqueous Acetic Acid ◽  
Sodium Perborate ◽  
Acetic Acid Medium

Kinetics and mechanism of oxidation of substituted 5-oxoacids by sodium perborate in aqueous acetic acid medium have been studied. The reaction exhibits first order both in [perborate] and [5-oxoacid] and second order in [H+]. Variation in ionic strength has no effect on the reaction rate, while the reaction rates are enhanced on lowering the dielectric constant of the reaction medium. Electron releasing substituents in the aromatic ring accelerate the reaction rate and electron withdrawing substituents retard the reaction. The order of reactivity among the studied 5-oxoacids is p-methoxy ≫ p-methyl > p-phenyl > –H > p-chloro > p-bromo > m-nitro. The oxidation is faster than H2O2 oxidation. The formation of H2BO3+ is the reactive species of perborate in the acid medium. Activation parameters have been evaluated using Arrhenius and Eyring’s plots. A mechanism consistent with the observed kinetic data has been proposed and discussed. Based on the mechanism a suitable rate law is derived.

scholarly journals Kinetics and mechanism of meso-tetraphenylporphyriniron(III) chloride (TPP) catalysed oxidation of indole by sodium perborate

2013 ◽  
Vol 15 (2) ◽  
pp. 107-111 ◽  
Author(s):  
D. Kungumathilagam ◽  
K. Karunakaran
Keyword(s):  
Acetic Acid ◽  
Catalytic Activity ◽  
Reaction System ◽  
Kinetic Scheme ◽  
Mechanistic Study ◽  
Radical Mechanism ◽  
Aqueous Acetic Acid ◽  
Sodium Perborate ◽  
Acetic Acid Medium ◽  
Catalysed Oxidation

Developing catalyst is very significant for biologically important reactions which yield products, used as drugs. Mechanistic study on meso-tetraphenylporphyriniron(III) chloride (TPP) catalysed oxidation of indole by sodium perborate in aqueous acetic acid medium have been carried out. The reaction follows a fractional order with respect to substrate and catalyst. The order with respect to oxidant was found to be one. Increase in the percentage of acetic acid and increase in the concentration of [H+] decreased the rate. The reaction fails to initiate polymerization, and a radical mechanism is ruled out. Activation and thermodynamic parameters have been computed. A suitable kinetic scheme based on these observations has been proposed. Significant catalytic activity is observed for the reaction system in the presence of TPP.

Titrimetric Determination of Iodine-Bromine Numbers of Some Edible Oils Using Three N-Chloroimides

1987 ◽  
Vol 70 (4) ◽  
pp. 762-763
Author(s):  
Narayanan Jayasree ◽  
Parameswaran Indrasenan
Keyword(s):  
Acetic Acid ◽  
Reaction Time ◽  
Solid State ◽  
Palm Olein ◽  
Edible Oils ◽  
Aqueous Acetic Acid ◽  
Acetic Acid Medium ◽  
Back Titration ◽  
Titrimetric Determination

Abstract Three simple titrimetric methods have been developed to determine iodine-bromine numbers of some edible oils, such as coconut, gingelly, groundnut, mustard, olive, palm olein, and sunflower, using 3 N-chloroimides. The 3 N-chloroimides are N-chlorophthalimide, N-chlorosuccinimide, and N-chlorosaccharin, all of which have recently been developed as potential oxidimetric titrants for use in aqueous acetic acid medium. The proposed excess back-titration methods have advantages over existing methods in terms of ease of extraction into aqueous acetic acid layer, shorter reaction time of NCSA method, and stability of N-chloroimides in solid state.

scholarly journals Meso-tetraphenylporphyriniron(iii) chloride catalyzed oxidation of aniline and its substituents by magnesium monoperoxyphthalate in aqueous acetic acid medium

2012 ◽  
Vol 14 (4) ◽  
pp. 35-41 ◽  
Author(s):  
Raja Manickam ◽  
Karunakaran Kulandaivelu
Keyword(s):  
Acetic Acid ◽  
Acid Medium ◽  
First Generation ◽  
Activation Parameters ◽  
Aqueous Acetic Acid ◽  
Substituted Anilines ◽  
Isokinetic Relationship ◽  
Acetic Acid Medium ◽  
Linear Free Energy ◽  
Energy Relationships

Abstract The catalytic properties of the first generation catalyst meso-tetraphenylporphyriniron(III) chloride and magnesium monoperoxyphthalate (MMPP) as oxidant have been studied in the oxidation of aniline and its substituents in acetic acid medium. The thermodynamic parameters for the oxidation have been determined and discussed. It confirms the Exner relationship (only at the low range of temperatures) and also some of the activation parameters to the isokinetic relationships. The magnesium monoperoxyphthalate oxidation with 18 ortho- meta- and para-substituted anilines fulfills with isokinetic relationship but not to any of the linear free energy relationships. The reaction mechanism and the rate law were proposed.

scholarly journals Kinetics of Oxidation of Some Amino Acids by N-Chlorosaccharin in Aqueous Acetic Acid Medium

2004 ◽  
Vol 1 (2) ◽  
pp. 127-131 ◽  
Author(s):  
N. A. Mohamed Farook ◽  
R. Prabaharan ◽  
S. Rahini ◽  
R. Senthil Kumar ◽  
G. Rajamahendran ◽  
...  
Keyword(s):  
Amino Acids ◽  
Acetic Acid ◽  
Acid Medium ◽  
Hypochlorous Acid ◽  
Activation Parameters ◽  
Slow Step ◽  
Aqueous Acetic Acid ◽  
Acetic Acid Medium ◽  
Kinetics Of Oxidation ◽  
Kinetics Of

The kinetics of oxidation of some amino acids namely, glycine, alanine, aspartic acid, arginine, and histidine, (AA) byN-chlorosaccharin (NCSA) in aqueous acetic acid medium in the presence of perchloric acid have been investigated. The observed rate of oxidation is first order in [AA], [NCSA] and of inverse fractional order in [H+]. The main product of the oxidation is the corresponding aldehyde. The ionic strength on the reaction rate has no significant effect. The effect of changing the dielectric constant of the medium on the rate indicates the reaction to be of dipole-dipole type. Hypochlorous acid has been postulated as the reactive oxidizing species. The reaction constants involved in the mechanism are derived. The activation parameters are computed with respect to slow step of the mechanism.

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