Aqueous Acetic Acid Medium Research Articles

Solvation model for the oxidation of methionine by imidazolium fluorochromate in aqueous acetic acid medium

The oxidation of methionine by imidazolium fluorochromate (IFC) were studied, in the presence of chloroacetic acid, in water-acetic acid mixtures of varying molar compositions. The reaction is first order with respect to methionine, IFC and acid. The reaction rates were determined at different temperatures and the activation parameters were computed. The reaction rate increases with increasing mole fraction of acetic acid in the mixture and specific solvent-solvent-solute interactions were found to predominate (86 %). A solvation model and a probable mechanism for the reaction are postulated.

Effect of solvent on the rate of oxidation of substituted anilines with nicotinium dichromate in aqueous-acetic acid media

Mechanistic studies on the oxidation of 15 para- and meta-substituted anilines by nicotinium dichromate in water-acetic acid medium of varying mole fractions have been performed. The reaction can be characterized by the experimental rate equation, -d[oxidizing agent] Kk [substrate] [HCrO - 4 ] dt (1 + K [substrate]) The addition of p-toluenesulfonic acid enhances the reaction. The oxidation substituted anilines at 299-322 K complies with the isokinetic relationship but not to any of the linear free energy relationships, the isokinetic temperature lies within the experimental range. Correlation of rate data with Kamlet-Taft solvatochromic parameters (a, β, π*) suggests that the specific solute-solvent interactions play a major role in governing the reactivity.

Evidence for synchronous cleavage of N-H and C-C bonds: bis(2,2¢-bipyridyl)copper(II) permanganate oxidation of cobalt(III) bound and unbound α-amino acids

Oxidation of pentaamminecobalt(III) complexes of α-aminoacids by bis(2,2'-bipyridyl) copper(II) permanganate in 50% HOAc-50% H 2 O (v/v) aqueous acetic acid medium. This oxidation as a diagnostic tool to find out the fraction proceeding by synchronous cleavages of N-H and C-C bonds.

A kinetic and mechanistic study on the oxidation of indole‐3‐acetic acid by peroxodisulfate

AbstractThe kinetics of oxidation of indole‐3‐acetic acid (IAA) by peroxodisulfate (PDS) has been carried out in aqueous acetic acid medium. First‐order dependence of rate each with respect to [IAA] and [PDS] was observed. The reaction rate was unaffected by added [H+]. Increase of percentage of acetic acid decreased the rate. Variation of ionic strength (μ) had negligible influence on the rate. A suitable kinetic scheme based on these observations involving a nonradical mechanism is proposed. The reactivity of peroxodisulfate toward indole‐3‐acetic acid was found to be lower than that with peroxomonosulfate. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 355–360, 2005

Kinetics and mechanism of oxidation of aliphatic alcohols by N-chloronicotinamide in aqueous acetic acid medium

Kinetics of oxidation of five aliphatic alcohols viz. n-butanol, n-propanol, n-pentanol, propan-2-ol and butan-2-ol by newly developed oxidant N-chloronicotinamide (NCN) in aqueous acetic acid medium in presence of HClO 4 and NaCl have been investigated. The observed rate of oxidation is first-order with respect to oxidant (NCN) and fractional-order with respect to alcohol. A decrease in the dielectric constant of the medium increases the rate. Addition of nicotinamide (NA), has a retarding effect on the rate of oxidation. The corresponding aldehydes and ketones are the major products of oxidation of primary and secondary alcohols respectively. From the effect of temperature on the reaction rate, the Arrhenius and the activation parameters have been calculated. A suitable mechanism has been proposed and a rate law explaining the experimental results is derived.

Kinetics and mechanism of oxidation of alcohols by piperidinium chlorochromate

Piperidinium chlorochromate is an efficient oxidizing agent for oxidation of primary alcohols to aldehydes. Kinetics of oxidation of alcohols to the corresponding carbonyl compounds have been studied in aqueous-acetic acid medium in presence of perchloric acid. The reaction shows first order kinetics each in [PipCC] and [H + ]. Michaelis-Menten type kinetics have been observed with respect to [alcohol]. The rate of oxidation decreases with increase in dielectric constant of solvent indicating ion-dipole interaction. The oxidation of alcohols by piperidinium chlorochromate gives corresponding aldehydes in good yields.

Simple one-pot conversion of organic compounds by hydrogen peroxide activated by ruthenium(III) chloride: organic conversions by hydrogen peroxide in the presence of ruthenium(III)

The aromatic compounds p-nitrobenzaldehyde, p-hydroxybenzaldehyde, naphthalene, toluene, catechol, quinol, aniline and toluidine dissolved in aqueous acetic acid or aqueous medium were oxidized in quantitative to good yields by 50% H2O2 in the presence of traces of RuCl3 (∼10−8 mol; substrate/catalyst ratio 1488:1 to 341 250:1). Conditions for highest yields, in the most economical way, were obtained. Higher catalyst concentrations decrease the yield. Oxidation in aromatic aldehydes is selective at the aldehydic group only. In the case of hydrocarbons, oxidation results in the introduction of a hydroxyl group with >85% (in the case of toluene) selectivity for the ortho position. Formation of low-molecular-weight polyaniline was reduced to 10%, along with 90% formation of higher molecular weight polyaniline. In this new, simple and economical method, which is environmentally safe and requires less time, oxo-centered carboxylate species of ruthenium(III) in acetic acid medium and hydrated ruthenium(III) chloride in aqueous medium probably catalyze the oxidation. Copyright © 2005 John Wiley & Sons, Ltd.

Kinetics of Oxidation of Cychlohexanol by N-Chloronicotinamide in Aqueous Acetic Acid Medium

Kinetics of oxidation o Cyclohexanol by N-Chloronicotinamide(NCN) in 50% V/V aqueous acetic acid mixture has been investigated in the presence of HCIO4 and NaCl. The observed rate of oxidation is first-order with respect to oxidation (NCN) and fractional-order with respect to cyclohexanol. A decrease in dielectric constant of the medium increases the rate. Addition of nicotinamide (NA), the reduction product of NCN, has a retarding effect an the rate of oxidation. Arrhenius and activation parameters are calculated. Kinetics of bromination1 and oxidation2,3 of saturated organic compounds by N-bromosuccinimide(NBS) have been received considerable attention. Kinetics and mechanism of oxidation of amino acids by NCN has been reported in aqueous acetic acid medium, we report herein the result of similar studies on the oxidation of cyclohexanol with NCN in aqueous acetic acid medium.

Kinetics of Oxidation of Some Essential Amino Acids by N‐Chlorosaccharin in Aqueous Acetic Acid Medium

The kinetics of oxidation of some essential amino acids namely, valine, leucine and phenylalanine, (AA) by N‐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

Kinetics of Oxidation of Some Amino Acids by N‐Chlorosaccharin in Aqueous Acetic Acid Medium

The kinetics of oxidation of some amino acids namely, glycine, alanine, aspartic acid, arginine, and histidine, (AA) by N‐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.

Cooxidation of anilides and oxalic acid by chromic acid: A one‐step, three‐electron oxidation

The chromic acid oxidation of a mixture of oxalic acid and anilides proceeds much faster than that of either of the two substrates alone. The oxidation kinetics of acetanilide, p-methyl-, p-chloro-, and p-nitroacetanilides by Cr(VI) in the presence of oxalic acid in aqueous acetic acid medium follows first-order, zero-order, and second-order dependence in [oxidant], [substrate], and in [oxalic acid], respectively, while the oxidation kinetics of benzanilide, p-methyl-, p-chloro-, and p-nitrobenzanilides follow first order in [oxidant] and fractional order each in [substrate] and [oxalic acid] and yields corresponding azobenzenes and benzaldehydes in the case of benzanilide and substituted benzanilides as the main products of oxidation. Aluminium ions suppress the reaction. The intermediate is believed to be formed from the anilide and a chromic acid-oxalic acid complex. In the proposed mechanism, the rate-limiting step involves the direct reduction of Cr(VI) to Cr(III). © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 33: 21–28, 2001

Kinetics and mechanism of oxidation of aldehydes by t-butyl hypochlorite in aqueous acetic acid medium

Kinetics and mechanism of oxidation of aldehydes by t-butyl hypochlorite in aqueous acetic acid medium

Cooxidation of anilides and oxalic acid by chromic acid: A one-step, three-electron oxidation

The chromic acid oxidation of a mixture of oxalic acid and anilides proceeds much faster than that of either of the two substrates alone. The oxidation kinetics of acetanilide, p-methyl-, p-chloro-, and p-nitroacetanilides by Cr(VI) in the presence of oxalic acid in aqueous acetic acid medium follows first-order, zero-order, and second-order dependence in [oxidant], [substrate], and in [oxalic acid], respectively, while the oxidation kinetics of benzanilide, p-methyl-, p-chloro-, and p-nitrobenzanilides follow first order in [oxidant] and fractional order each in [substrate] and [oxalic acid] and yields corresponding azobenzenes and benzaldehydes in the case of benzanilide and substituted benzanilides as the main products of oxidation. Aluminium ions suppress the reaction. The intermediate is believed to be formed from the anilide and a chromic acid-oxalic acid complex. In the proposed mechanism, the rate-limiting step involves the direct reduction of Cr(VI) to Cr(III). © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 33: 21–28, 2001

Study of interactive free-energy relationships on ruthenium(III) catalyzed oxidation of phenyl styryl ketone and its substituted analogues by V(V) in acid medium

Kinetics of Ru(III) catalyzed oxidation of phenyl styryl ketone (PSK) and its substituted analogues by V(V) has been investigated in aqueous acetic acid-sulphuric acid medium in the temperature range 298–313 K. First-order dependence each on [V(V)], [PSK], [Ru(III)] was observed. Inverse first-order dependence was observed for [V(IV)]. The rate decreased with the increase in dielectric constant (D) of the medium. The rates were enhanced by electron-donating substituents in both the phenyl rings and decreased by electron-withdrawing substituents. Linear Hammett's plots were obtained for various substituents in benzaldehyde moiety of PSK for a given substituent in acetophenone moiety and vice versa. The mechanism proposed envisages formation of Ru(IV) from V(V) + Ru(III) reaction followed by the attack on by Ru(IV). Applicability of interactive free-energy relationship has been tested. The cross-interaction constants qx and qy have been determined at different temperatures and possible interpretations discussed. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 581–588, 2000

Kinetics and mechanism of oxidation of amino acids by N-chloronicotinamide in aqueous acetic acid medium

Kinetics and mechanism of oxidation of amino acids by N-chloronicotinamide in aqueous acetic acid medium

Kinetic and mechanistic studies on the oxidation of Norfloxacin by Chloramine-B and N-Chlorobenzotriazole in acidic medium

The kinetics of oxidation of Norfloxacin [1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(l-piperazinyl)-3-quinoline carboxylic acid] by chloramine-B and N-chlorobenzotriazole has been studied in aqueous acetic acid medium (25% v/v) in the presence of perchloric acid at 323 K. For both the oxidants, the reaction follows a first-order dependence on [oxidant], a fractional-order on [Norfloxacin], and an inverse-fractional order on [H+]. Dependence of reaction rate on ionic strength, reaction product, dielectric constant, solvent isotope, and temperature is studied. Kinetic parameters are evaluated. The reaction products are identified. The proposed reaction mechanism and the derived rate equation are consistent with the observed kinetic data. Formation and decomposition constants for substrate–oxidant complexes are evaluated. ©1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 153–158, 1999

Anodically Generated Manganese(III) Oxidation of L-Serine and DL-Threonine in Aqueous Acetic Acid Medium: Kinetics and Mechanism

Manganese(III) acetate solutions were prepared by electrolytic oxidation of Mn(OAc)2 in aqueous HOAc. The electrogenerated Mn(III) species was characterized by spectroscopic and redox potential studies. The kinetics of oxidation of the α-amino acids (AA) L-serine and DL-threonine by Mn(III) ions have been studied in aqueous HOAc medium at 323 K. The reaction follows the following rate law: rate = k1 [Mn(III)]1/2 [AA] [H+]x− [OAc−]y where k′ = rate constant and x = y = fractional. Variation of the concentration of the reduction product Mn(II) had no effect on the reaction rate. Added anions such as F−, Cl− and CIO4 − affected the rate by changing the formal redox potential of the Mn(III)-Mn(II) couple. The effect of varying the solvent composition with HOAc was studied. Kinetic studies showed that the reaction rate decreased in D2O (40% v/v) giving solvent isotope effects of k′H2O/k′D2O = 1.46 and 1.69 for serine and threonine, respectively. Activation parameters have been evaluated using the Arrhenius and Eyring plots. A mechanism consistent with the kinetic data has been proposed. The kinetic data for the oxidation of some α-amino acids by various Mn(III) species are summarized and compared. Referee I: J. Castillo Referee II: T. J. Meyer

Kinetics and mechanism of oxidation of substituted benzaldehydes by quinolinium fluorochromate

The kinetics of oxidation of a number of meta- and para-substituted benzaldehydes by quinolinium fluorochromate, QFC has been studied in aqueous acetic acid medium in the presence of acid. The products of oxidation are the corresponding benzoic acids. The reaction is first order each in substrate, QFC and HClO4. Electron-withdrawing substituents increase the rate, while electron-releasing substituents decrease it and the rate data obey Hammett's relationship. The reaction constant ϱ for the oxidation has a value of 1.16±0.07 at 30°C. The activation enthalpies and entropies are calculated and the possible mechanism for oxidation is discussed.

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

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.

Kinetics of oxidation of pyridoxine by anodically generated manganese(III) in aqueous acetic acid medium

Manganese(III) acetate was prepared by the electrolytic oxidation of Mn(OAc)2 in aqueous AcOH. The electro-generated manganese(III) species was characterised by spectroscopic and redox potential studies. The kinetics of oxidation of pyridoxine (PRX) by manganese(III) in aqueous AcOH were investigated and is first order with respect to [MnIII]. The effects of varying [MnIII], [PRX], added manganese(II), pH and added anions such as AcO−, F−, Cl− and ClOinf4sup−and SOinf4sup2−were studied. The rate decreased slowly with increasing [H+] up to 0.2 mol dm−3 and increased steeply thereafter. The orders in [PRX] and [MnII] were unity and inverse fractional, respectively, in both low and high [H+] ranges. The dependence of reaction rate on temperature was studied and activation parameters were computed from Arrhenius and Eyring plots. A mechanism consistent with the observed results is proposed and discussed.