Aqueous Acetic Acid Medium Research Articles

Reactivity of Benzyl Alcohol and Substituted Benzyl Alcohols with 1-Chlorobenzimidazole in Acid Medium – A Kinetic and Mechanistic Approach

<div><p><em>The kinetics of oxidation of benzyl alcohol and a few substituted benzyl alcohols with 1-chlorobenzimidazole (CBI) were studied in aqueous acetic acid medium. The order of the reactions with respect to each oxidant and substrate was found to be unity. The added HClO<sub>4</sub> increases the rate and the order in [HClO<sub>4</sub>] was found to be fractional. The reactions were catalyzed by NaCl and a fractional order dependence was observed for [NaCl]. The ionic strength had negligible influence on the rate. Increase in the percentage of acetic acid increases the rate. Addition of benzimidazole, one of the products does not affect the rate. Effect of temperature on the reaction rates was studied at different temperatures and the various activation and thermodynamic parameters were computed. The Hammett plot shows an excellent correlation with negative ρ value (- 0.37) for benzyl alcohols. Product analysis shows the formation of aldehydes as major products of oxidation of benzyl alcohols. CBIH<sup>+</sup> has been postulated as the reactive oxidizing species. Suitable mechanism and the rate law in consistent with the experimental results have been proposed.</em></p></div>

Kinetics of Oxidation of 3-Benzoylpropionic Acid by N-Chloroacetamide in Aqueous Acetic Acid Medium

Kinetics of Oxidation of 3-Benzoylpropionic Acid by N-Chloroacetamide in Aqueous Acetic Acid Medium

Kinetics and Mechanism of Oxidation of Aliphatic Primary Alcohols with 1-Chlorobenzimidazole in Aqueous Acetic Acid Medium

Abstract The kinetics of oxidation of a few aliphatic primary alcohols with 1-chlorobenzimidazole (CBI) was studied in aqueous acetic acid medium. The reactions were found to be first order each with respect to the concentrations of CBI and alcohol. The added HClO4 increases the rate and the order in HClO4 was found to be fractional. The reactions were catalyzed by NaCl and fractional order dependence was observed. The ionic strength had negligible influence on the rate. The reaction rates increase with decrease in dielectric constant of acetic acid. Addition of benzimidazole, one of the products does not affect the rate. Effect of temperature on the reaction rates was studied at different temperatures and the various activation and thermodynamic parameters were evaluated. The rate constants show good correlation with Taft–Pavelich Dual substituent parameter model (DSP). Product analysis shows the formation of aldehydes as major products of oxidation of aliphatic primary alcohols. CBIH+ has been postulated as the reactive oxidizing species. A mechanism involving a proton transfer by water molecule has been proposed.

Micellar Catalysed Kinetic Oxidation Study of Acetophenone by N-Bromosaccharin in Aqueous Acetic Acid Medium

Micellar Catalysed Kinetic Oxidation Study of Acetophenone by N-Bromosaccharin in Aqueous Acetic Acid Medium

Reactivity of Phenol and Aniline towards Quinolinium Chloro Chromate: A Comparative Oxidation Kinetic Study

The kinetics of Oxidation of Phenol and aniline by quinolinium Chlorochromate (QCC) in aqueous acetic acid medium leads to the formation of quinone and azobenzene respectively. The reactions are first order with respect to both Phenol and aniline. The reaction is first order with respect to quinolinium chlorochromate (QCC) and is catalyzed by hydrogen ion. The hydrogen-ion dependence has the form: kobs = a+b [H+]. The rate of oxidation decreases with increasing dielectric constant of solvent, indicating the presence of an ion-dipole interaction. The reaction does not induced the polymerization of acrylonitrile. The retardation of the rate by the addition of Mn2+ ions confirms that a two electron transfer process is involved in the reaction. The reaction rates have been determined at different temperatures and the activation parameters have been calculated. From the above observations kinetic results a probable mechanism have been proposed.

Reactivity of Phenol and Aniline towards Quinolinium Chloro Chromate: A Comparative Oxidation Kinetic Study

The kinetics of Oxidation of Phenol and aniline by quinolinium Chlorochromate (QCC) in aqueous acetic acid medium leads to the formation of quinone and azobenzene respectively. The reactions are first order with respect to both Phenol and aniline. The reaction is first order with respect to quinolinium chlorochromate (QCC) and is catalyzed by hydrogen ion. The hydrogen-ion dependence has the form: kobs = a+b [H+]. The rate of oxidation decreases with increasing dielectric constant of solvent, indicating the presence of an ion-dipole interaction. The reaction does not induced the polymerization of acrylonitrile. The retardation of the rate by the addition of Mn2+ ions confirms that a two electron transfer process is involved in the reaction. The reaction rates have been determined at different temperatures and the activation parameters have been calculated. From the above observations kinetic results a probable mechanism have been proposed.

Kinetics and the mechanism of oxidation of methoxy benzaldehydes by benzimidazolium fluorochromate in an aqueous acetic acid medium

The oxidation of benzaldehyde (BA) as well as 4-methoxy (4-MBA), 3-methoxy (3-MBA), 2-methoxy (2-MBA), 2,6-dimethoxy (2,6-DMBA), 2,4-dimethoxy (2,4-DMBA), 3,4-dimethoxy (3,4-DMBA), 2,4,6-trimethoxy (2,4,6-TMBA), 3,4,5-trimethoxy (3,4,5-TMBA) and 2,3,4-trimethoxy (2,3,4-TMBA) benzaldehydes by benzimidazolium fluorochromate (BIFC) have been studied in a 50% acetic acid–50% water medium. The oxidation leads to the formation of the corresponding carboxylic acids. The reaction is first order with respect to [BIFC], [S] and [H+]. The reaction was catalysed by H+ ions. The reaction was studied at four different temperatures, and the thermodynamic parameters were calculated. The Exner plot indicated that all of the methoxy-substituted benzaldehydes were oxidized via the same mechanism. Based on the observed kinetics, a suitable mechanism has been proposed.

Kinetics of Oxidation of 3-Benzoylpropionic Acid by N-Bromobenzamide in Aqueous Acetic Acid Medium

Kinetics of Oxidation of 3-Benzoylpropionic Acid by N-Bromobenzamide in Aqueous Acetic Acid Medium

X-Ray Diffraction Studies of some Structurally Modified Indian Coals and their Correlation with Petrographic Parameters

In order to study the X-ray structural parameters, five coals have been chosen from different coal basins of India. These coals have been demineralized by standard HF + HCl treatment and treated with nitric acid in aqueous and glacial acetic acid media. X-ray diffraction (XRD) patterns of the samples are recorded using a slow step scan (2 s/step) over an angular range 2θ ∼ 10-90°. TOPAS software has been used to determine the structural parameters like interlayer spacing ( d 002 ), crystallite size ( L c ), aromaticity ( f a ) and average number of aromatic layers ( N c ). The structural parameters have been correlated with chemical as well as petrographic parameters of coals. Mean random reflectance (MR r ) of the studied coals varies between 0.44% and 0.54% and the vitrinite, liptinite and inertinite contents vary between 17.8% and 66.4%, 9.2% and 20.3% and 20.7% and 62.9% respectively. Nitration in both the media has increased d 002 values. This study also shows that d 002 and fa values are dependent on the rank of the coal, rather than only the carbon content ( C dmf , dry mineral free basis). XRD rank parameter values have been directly correlated with the petrographic rank parameters. Nitration in both the media has induced similar kind of effect on individual macerals. Behaviour of the macerals to chemical treatment is also reported in this study.

Kinetics and Mechanism of Oxidation of some α - Hydroxy Acids by Tripropylammonium Fluorochromate in Aqueous Acetic Acid Medium

The oxidation of some α-hydroxy acids like glycolic, lactic and mandelic acids by tripropylammonium fluorochromate (TriPAFC) have been studied in aqueous acetic acid medium. The oxidation leads to the formation of the corresponding oxo acids. The reaction is first order with respect to TriPAFC, hydroxy acids and (H + ) and the reaction is catalyzed by hydrogen ions. The reaction has been studied in different percentage of acetic acid-water mixture. A suitable mechanism has been proposed.

Preparation of Chitosan Copper Complexes: Molecular Dynamic Studies of Chitosan and Chitosan Copper Complexes

This work studied the effect of copper ions concentration chelated by functional groups in chitosan on its molecular dynamic. Chitosan Copper complexes prepared having different copper concentrations by the electrochemical oxidation technique in aqueous-acetic acid medium. It was carried out at constant voltage (2 volt.) at room temperature at different electro-oxidation time. The result of partial elemental analysis and XRD studies of chitosan copper complexes compared with chitosan confirmed that the percentage composition of the complexes were found to be depend on the time of electrolysis which is in good agreement with our previous work. Interpretation of the effect of copper ions concentration on molecular motion of chitosan studied using dielectric spectroscopy, the results showed that dielectric constant of chitosan is higher than that of chitosan copper complexes. This may be attributed to the relatively fast segmental motion of chitosan chain slowed down by complexation with copper ions of all complex samples. Calculated activation energy from Arrhenius variation showed increase in value with increasing the copper concentration and all in the range that required for ionic conduction. Temperature dependence part of dielectric parameters gives very useful representation in the glass transition temperature determination.

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

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.

Oxidation of Aromatic Anils by Sodium Perborate in Aqueous Acetic Acid Medium

Oxidation of Aromatic Anils by Sodium Perborate in Aqueous Acetic Acid Medium

Synergy effect between solid acid catalysts and concentrated carboxylic acids solutions for efficient furfural production from xylose

An efficient furfural formation from xylose was demonstrated combining a concentrated aqueous solution of acetic acid and solid acid catalysts. Higher furfural yields and selectivities were obtained by comparison to the catalytic performances obtained in pure water. The evident synergy effect observed at 150°C between the aqueous carboxylic acid solution and the solid acid catalysts is tentatively explained by the occurrence of two phenomena: 1) the contribution of Lewis acid sites which would operate in cooperation with the homogeneous weak Brønsted acidity brought by the aqueous acetic acid solution. According to the literature, the two steps mechanism involving the xylose-xylulose isomerization over Lewis acid sites and the successive Brønsted acid catalyzed cyclodehydration to furfural would be the prevailing reaction pathway in the heterogeneous–homogenous catalytic system at 150°C. 2) an enhancement of the surface solid acid coverage by the carbohydrate and furfural owing to the presence of carboxylic acid in the aqueous solution as shown by comparative liquid phase adsorption experiments done in pure water and in aqueous acetic acid solutions. Among a series of solid acid catalysts, ZrW, Cs2HPW12O40, HY (Si/Al=15), K10 and NbOH, the latter one, NbOH used non-calcinated was shown to be active, selective and stable in the aqueous acetic acid media. HY and K10 are as active and selective for furfural formation but suffer for a strong Al leaching which precludes their utilization as true solid acid catalyst in acetic acid media.

Kinetics of Oxidation of Amino Acids by a Newly Synthesized Oxidant, N-Chloropyrazinamide in Aqueous Acetic Acid Medium

The kinetics of oxidation of amino acids namely, alanine, glycine, leucine, phenyl alanine and valine by N-chloropyrazinamide (NCPZA) in aqueous acetic acid medium in the presence of hydrochloric acid have been investigated. The observed rate of oxidation is first order in [NCPZA], [H+] and [Clˉ]. The order with respect to [amino acid] is zero. The rate of oxidation increases with increase in the percentage of acetic acid. The reaction rate increases slightly with increase in ionic strength, while retards with addition of pyrazinamide. Arrhenius and thermodynamic activation parameters have been evaluated from Arrhenius plot by studying the reaction at different temperatures. A most probable reaction mechanism has been proposed and an appropriate rate law is deduced toaccount for the observed kinetic data.

Kinetic investigation of oxidation of aromatic anils by magnesium monoperoxyphthalate in aqueous acidic medium

Abstract The kinetics of oxidation of aromatic anils to benzaldehyde and azobenzene by magnesium monoperoxyphthalate (MMPP) has been studied in aqueous acetic acid medium. The low dielectric constant of the medium facilitates the reactivity. It has been found that ionic strength of the reaction has no significant effect on rate. The added acrylonitrile has no effect on the reaction rate indicating the absence of free radical mechanism. The added Mn(II) decreases the rate of the reaction, which indicates the involvement of two-electron transfer. Highly negative ΔS# values indicate a structured transition state. The deviation of Hammett plot is noted and a non-linear concave downward curve is obtained for the anils with substituents in the aniline moiety. The observed break in the log kobs versus σ is attributed to the transition state whereas the non-linear concave upward curve is observed for the substituents in the benzaldehyde moiety and a non-linear concacve upward curve is observed for the substituents in the combination of aniline and benzaldehyde moiety and a suitable mechanism is proposed

Kinetics of Oxidation of Amino Acids by a Newly Synthesized Oxidant, N-Chloropyrazinamide in Aqueous Acetic Acid Medium

The kinetics of oxidation of amino acids namely, alanine, glycine, leucine, phenyl alanine and valine by N-chloropyrazinamide (NCPZA) in aqueous acetic acid medium in the presence of hydrochloric acid have been investigated. The observed rate of oxidation is first order in [NCPZA], [H+] and [Clˉ]. The order with respect to [amino acid] is zero. The rate of oxidation increases with increase in the percentage of acetic acid. The reaction rate increases slightly with increase in ionic strength, while retards with addition of pyrazinamide. Arrhenius and thermodynamic activation parameters have been evaluated from Arrhenius plot by studying the reaction at different temperatures. A most probable reaction mechanism has been proposed and an appropriate rate law is deduced toaccount for the observed kinetic data.

Kinetics and Mechanism of meso -Tetraphenyl-porphyriniron (III) Chloride Catalyzed Oxidation of Aniline and Its Substituents by Oxone in Aqueous Acetic Acid Medium

Metalloporphyrins are present naturally in cytochromes and hemoglobins. Perhaps the most interesting feature of heme-enzymes, such as cytochromes P450, is their ability to perform extremely difficult oxidations with high selectivity. The present work is undertaken with the aspiration of designing the mechanistic studies on meso-tetraphenylporphyriniron(III) chloride catalyzed oxidation of anilines by potassium peroxymonosulfate (oxone) in aqueous acetic acid medium. The study of oxidation with respect to the catalyst reveals that there is degradation of the catalyst. The concentration-protonated aniline (a less reactive species) increases due to the increase in [H+], which inhibits the rate of the reaction. The thermodynamic parameters for the oxidation have been determined and discussed. It confirms the Exner relationship and also the activation parameters to the isokinetic relationships. The oxone oxidation with 12 meta- and para-substituted anilines complies with the isokinetic relationship but not with any of the linear free energy relationships. The solvent interaction plays a major role in governing the reactivity. A suitable mechanism is proposed for this reaction.

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

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.

Kinetics and Mechanism of the Oxidation of 4-Oxo-4-arylbutanoic Acids by N-bromophthalimide in Aqueous Acetic Acid Medium

The kinetics of oxidation of a series of substituted 4-oxobutanoic acids (Y–C6H4COCH2CH2COOH: Y = H, OCH3, CH3, C6H5, Cl, Br or NO2) by N-bromophthalimide have been studied in aqueous acetic acid medium at 30 °C. The total reaction is second-order, first-order each in oxidant and substrate. The oxidation rate increases linearly with [H+], establishing the hypobromous acidium ion, H2O+Br, as the reactive species. A variation in ionic strength has no effect on the reaction rate. The order of reactivity among the studied 4-oxoacids is: 4-methoxy > 4-methyl > 4-phenyl > 4-H > 4-Cl > 4-Br > 3-NO2. The effect of changes on the electronic nature of the substrate reveals that there is a development of positive charge in the transition state. The activation parameters have been computed from Arrhenius and Eyring plots. Based on the kinetic results, a suitable mechanism has been proposed.