Perchloric Acid Medium Research Articles

A Study of Micellar Catalyses on Oxidation of Glycine by QDC in the Presence of Sodium Dodecyl Sulphate (SDS) in Aqueous Perchloric Acid Medium

Aims: To study the micellar effect of SDS on the oxidation of glycine by Quinolinium Dichromate (QDC) in perchloric acid medium. Background: Among the amino acids, glycine plays a major role in multiple metabolic reactions, such as glutathione synthesis and one-carbon metabolism. The oxidation of glycine has received importance because it is the major neurotransmitter inhibitor in the spinal cord and brainstem. In the oxidation process of amino acids, highly toxic chromium (VI) compounds are converted into non-toxic chromium (III) by quinolinium dichromate (QDC) oxidant in an appropriate pH value medium. Objective: 1. To study the catalytic role of anionic surfactant (SDS) on the oxidation of glycine by QDC through micellization, evaluation of critical micelles concentration (CMC) in the presence and absence of glycine and other surface properties along with thermodynamic quantities. 2. Determination of rate constant and order of reaction with respect to QDC, glycine, acid and surfactant which will help to study the kinetics of the reaction 3. Analysis of oxidation product by FT-IR and calculation of activation parameters. 4. Synthesis of oxidant (QDC) and its characterization by UV-Visible spectrophotometer and NMR spectroscopy. Results: First-order kinetics was observed with respect to oxidant, glycine and hydrogen ions. The rate of reaction increased remarkably with an increase in the concentration of surfactant (SDS). The kinetic results show that the ionic strength variation does not have any significant effect on the rate whereas the increase in the dielectric constant of the medium shows a remarkable effect on the rate constant. From stoichiometry study, it was found that 2 moles of oxidant (QDC) consumed 3 moles of glycine to produce aldehyde (Formaldehyde). Conclusion: The observed negative value of (ΔS) entropy of activation and positive (ΔH) enthalpy of activation suggests a more ordered activated complex formation and highly solvated transition state. The kinetics of the reaction in a perchloric acid medium is found to be accelerated in the presence of surfactant (SDS). The kinetics of the reaction follow pseudo first-order decay of Cr(VI) species (QDC), a unity dependence of rate on glycine and perchloric acid. The oxidation product formaldehyde was identified by FTIR. NMR spectrum analysis of synthesized QDC shows a resemblance with pure QDC.

Redox Kinetics and Mechanism of the Reactions of µ –Oxobis [aquobis (2,2’ – Bipyridine)] diruthenium (III) Ion and some Aliphatic Alcohols in Acidic Medium

The redox kinetics and mechanisms of the reactions of μ – oxobis[aquobis(2,2’ - bipyridine)]diruthenium (III) ion, [(bipy)2(H2O)RuORu(H2O)(bipy)2]4+ (hereafter denoted as Ru2O4+ or [(H2O)2(bipy)4Ru2O]4+) and some primary aliphatic alcohols was studied in perchloric acid medium, [H+] = 5.0 x 10-3 mol dm-3, ionic strength (I), = 0.5 mol dm–3 (NaClO4), temperature (T) = 31 ± 1°C and wavelength ,λmax = 660 nm. The reactions, which led to the formation of corresponding aldehydes had a stoichiometry of 1:1, were all first order with respect to each reactant, and second order overall. The reactions proceeded in the absence of acid but when acid was added, the reactions ceased. Varying the ionic strength and dielectric constants of the reaction medium had no effect on the reaction. Added ions catalysed the reaction and free radicals were identified in the reaction mixtures in the course of the reactions. There was no evidence for the formation if intermediate complex in the course of the reaction. The order of reactivity is of the order CH3OH > C2H5OH > C3H7OH Based on the results, it is suggested that all the reactions proceeded through the outer – sphere electron transfer mechanism and a plausible mechanism that represented all the reactions is proposed.

WITHDRAWN: Kinetics and mechanism of the reactions of alkanediamine-linked dinuclear platinum(II) complexes with some biorelevant-nucleophiles

The kinetics and mechanism of substitition reactions of dinuclear platinum(II) complexes of the general formula [{Pt(H2O)}2(N,N,N′,N′-tetrakis(2-pyridylmethyl)-N(CH2)n-N](ClO4)4,viz., n = 2 (PtEn); 3 (PtProp); 6 (PtHex); 8 (PtOct) and 10 (PtDec) were investigated in 0.10 M aqueous perchloric acid medium as a function of concentration of l-glutathione (Glu) and dl-penicilliamine (Pen) nucleophiles and temperature under pseudo first-order conditions using UV–visible spectrophotometry. The reactivity data of the dinuclear Pt(II) complexes were compared with those of their mononuclear analogues of the form [Pt(H2O)(N,N-bis(2-pyridylmethyl)-N(CH2)n-CH3](ClO4)2, n = 1 (Ptbpea); 2 (Ptbppa); 5 (Ptbpha) and 9 (Ptbpda) under the same experimental conditions. The observed rate constants for the substitution of the aqua ligands follow the simple rate law: kobs = k2[Nu]. The reactivity of the complexes increases as the chain length of the linker or tail increases except Prop which showed a higher reactivity towards the nucleophiles than the rest of the complexes. The overall trend of reactivity for the dinuclear platinum(II) complexes is PtEn < PtHex < PtOct < PtDec < PtProp. The reactivity of the mononuclear complexes follows the same trend as the dinuclears and increases in the order Ptbpea < Ptbppa < Ptbpha < Ptbpda. In all cases, the mononuclear complexes are more reactive than their dinuclear analogues, which is an indication of the steric retardation on the rate of substitution due to the conformations of the dinuclear platinum(II) complexes. Glu was found to be a better nucleophile than Pen. The relatively small and positive values for the enthalpy of activation, negative values for entropy of activation and the dependence of the second-order rate constants on the concentration of entering nucleophiles supports an associatively activated mechanism.

Experimental and theoretical studies of aminothiophene derivatives inhibitors on carbon steel corrosion in perchloric acid medium

The effect of two aminothiophene derivatives, namely (2-amino-4-phenylthiophene-3-carbonitrile) APTC and (2-amino-4-p-tolylthiophene-3-carbonitrile) ATTC, as carbon steel corrosion inhibitors in a perchloric acid medium was investigated. The study was performed by weight loss method, quantum chemical calculations (DFT) and Scanning electron microscope (SEM). The impact of the two aminothiophene derivatives as inhibitors was positively correlated with concentration, temperature, and exposure time. The value of the active energy of the inhibition corrosion reaction of carbon steel is greater than that obtained for the blank solution. All experimental data were consistent with the Langmuir adsorption isotherm, and the value and sign of the adsorption free energy obtained indicated that the inhibitor molecules were spontaneously adsorbed on the carbon surface by a mixed adsorption mechanism. The SEM surface analysis showed the formation of a protective organic film on the steel surface. The DFT supported the experimental results and showed that the inhibition effect is structure-dependent.

Waugh Type Polyoxometalate Enneamolybdomangate(IV) as an Acid Catalyst for Hydrolysis and as an Oxidant for Aspirin: A Kinetic Study

The oxidations of aspirin and salicylic acid by enneamolybdomanganate(IV) were studied in perchloric acid medium. The aspirin undergo hydrolysis prior to the oxidation to generate salicylic acid, which was found to be catalyzed by both HClO4 as well as the oxidant. The rate of hydrolysis of aspirin catalyzed by the oxidant was found to be lesser than that of HClO4. A mechanism based on the kinetic results is proposed for oxidation of both aspirin and salicylic acid. Initially, aspirin undergo hydrolysis to give salicylic acid, which is catalyzed by both the oxidant, which also acts as an acid catalyst and the HClO4 used. The salicylic acid generated in prior hydrolysis reacts with an oxidant undergoing oxidative decarboxylation by enneamolybdomanganate(IV) in a rate determining step generating phenol. Further oxidation of phenol by another oxidant molecule gives the final product p-benzoquinone in a fast step. The mechanism of oxidation of salicylic acid was also studied under identical conditions as that of aspirin and found to be similar except its prior hydrolysis. A plausible mechanism was proposed and the rate laws for both the substrates were derived. In order to understand the intervention of free radicals the reaction was studied in presence of added acrylonitrile. The formation of copious precipitate due to polymerization of added acrylonitrile was not observed and the values of kobs also remain constant in presence of added acrylonitrile. The formation of MnIII was also studied in presence of added tetrasodium pyrophosphate, which did not affect the values of kobs. Therefore, the formation of free radical and MnIII was excluded while proposing mechanisms for both the substrates. The effect of added products Mn2+ and molybdate also did not have any effects indicating no prior equilibria involving these two products. The effect of ionic strength and solvent polarity are in favour of the reaction between two neutral molecules. The activation parameters were determined and support an outer sphere reaction with formation of a weak precursor complex between the reactants was proposed for both aspirin and salicylic acid.

Kinetics and oxidation of thiocarbohydrazide by hexacyanoferrate(III) in aqueous perchloric acid medium

Hexacyanoferrate(III) [HCF(III)] was used to oxidize thiocarbohydrazide (TCH) in an aqueous perchloric acid (HClO4) medium, and the reaction kinetics were studied spectrophotometrically at 420 nm while keeping a constant ionic strength of 1.0 mol dm−3 and modulating the temperature between 298K–318K. The stoichiometry of the reaction among TCH and HCF in the HClO4 medium is 1:2. The reaction has a lower than unit order in both TCH and HClO4 and is of the first order in HCF. The impact of varying the ionic strength and dielectric constant of the medium on the rate has been investigated. The effect of temperature on the reaction rate was studied, and different activation parameters of reaction Ea, ΔH#, ΔS#, ΔG#, and log10 A were calculated. The products of oxidation were analyzed by simple qualitative analysis. On the basis of the collected data, the rate law has been derived, and a probable mechanism has been proposed.

The Kinetics and Mechanism of Oxidation of Cinnamyl Alcohol by N-Chloro p-toluene Sulphonamide (Chloramine-T) in Acid Perchlorate Medium

The Kinetics and Mechanism of Oxidation of Cinnamyl Alcohol by N-Chloro p-toluene Sulphonamide (Chloramine-T) in Acid Perchlorate Medium

Oxidation of paracetamol by N-chloro-p-toluene sulfonamide (Chloramine-T) in aqueous acid perchlorate medium: A kinetic and mechanistic pathway

Oxidation of paracetamol by N-chloro-p-toluene sulfonamide (Chloramine-T) in aqueous acid perchlorate medium: A kinetic and mechanistic pathway

Sorption of Actinides in Various Oxidation States on TODGA-Containing TVEX from Nitric, Hydrochloric, and Perchloric Acid Media

Sorption of Actinides in Various Oxidation States on TODGA-Containing TVEX from Nitric, Hydrochloric, and Perchloric Acid Media

Kinetics and Mechanism of Ruthenium(III) Chloride Catalyzed Oxidation of Cinnamyl Alcohol by Thallium(III) in Acid Perchlorate Medium

Kinetics and Mechanism of Ruthenium(III) Chloride Catalyzed Oxidation of Cinnamyl Alcohol by Thallium(III) in Acid Perchlorate Medium

Kinetics and mechanistic studies for the oxidation of N-Benzylhydroxylamine by a CoIII-bound bridging superoxo complex in perchloric acid medium

In aqueous perchloric acid medium (pH = 0.522 – 1.3) , N–benzylhydroxylamine ( two electron reductant) reduces the one electron oxidant, superoxo ligand in [(dien)(en)CoIII(O2)CoIII(en)(dien)](ClO4)5 (1) to the corresponding hydroperoxo complex, [(en)(dien)CoIII(HO2)CoIII(en)(dien)]5+ (2) and itself gets oxidised to PhCH2NO following both proton coupled electron transfer (PCET) path and an electron – transfer (ET) reaction. The kinetics, stoichiometry and reaction mechanism clearly indicate that oxidation of PhCH2NHOH occurs through the formation of an intermediate, benzyl derivative of aminoxyl radical (PhCH2NHO•). In the presence of excess PhCH2NHOH over 1, the reaction obeys first-order kinetics and rate of the reaction increases with [PhCH2NHOH]. The reaction rate, however, decreases with increase in [H+] and the plot of 1/ko with [H+] is linear with a small but noteworthy intercept. It is also remarked that the reaction rate remarkably decreases with increasing proportion of D2O replacing H2O in the solvent. Therefore, an H-atom transfer (HAT) from PhCH2NHOH to the bridging superoxide in 1 seems reasonable at the rate determining step.

Exploration of Ruthenium (III) Chloride catalysis on oxidative conversion of aryloximes to arylaldehydes with bromamine-B: A kinetic and mechanistic approach

Conversion of aryloximes to corresponding arylaldehydes is an important oxidative transformation in synthetic chemistry. In the course of this research, optimum conditions for the facile oxidation of benzaldehyde oxime and p-substituted benzaldehyde oximes viz., p-hydroxybenzaldehyde oxime, p-methoxy benzaldehyde oxime, p-bromobenzaldehyde oxime and p-nitrobenzaldehyde oxime (aryloximes) with bromamine–B (BAB) catalyzed by ruthenium (III) chloride (RuCl3) in perchloric acid (HClO4) medium have been kinetically investigated at 303 K. All the five aryloximes follow identical kinetics with a first-order dependence of rate on [BAB]o, fractional-order each on [aryloximes]o and [RuCl3], and an inverse fractional-order on [H+]. Activation parameters have been evaluated. Oxidation products were characterized by spectral analysis. Under the identical set of experimental conditions, the kinetics of catalyzed reactions has been compared with uncatalyzed reactions and found that the catalyzed reactions are 4–6 folds faster. Isokinetic temperature is found to be 338 K. The catalytic constants (Kc) have been calculated at different temperatures and the values of activation parameters with respect to the catalyst have been evaluated. Spectroscopic evidence for the formation of 1:1 complex between BAB and RuCl3 has been obtained. The observed results have been explained by a plausible mechanism and the related rate law has been deduced. The present method offers many advantages including high conversion, short reaction times and the involvement of non-toxic reagents.

Highly Ordered Nanotube Arrays as Photo-Anodes for Dye-Sensitized Solar Cells by Electrochemical Method

Symmetrically packed TiO2 nanotubes (TNTs) were fabricated in fluorine free perchloric acid medium by electrochemical anodization method. During anodization interconnected pores developed by forming amorphous/ hydroxides of titanium film. On increasing anodization, thickness of film increased and pores tend to become aligned providing surface layer of nanotubes on the electrode material. The 1-D charge carrier transport property of the tubular geometry have attracted scientists attention in using TNTs for TiO2 photovoltaic and photo catalysis applications. By controlling the anodization process, the length, diameter and wall thickness of TNTs can be tailored. The iron and chromium doped highly ordered 1-D TNTs obtained during anodization are superior photoanodes for dye-sensitized solar cells because of its reduced inter tube connections, vertical electron transport, suppressed electron recombination and enhanced current density, efficiency in power conversion and light scattering. The morphological characteristics and microstructure of TNTs were investigated by SEM and X-ray diffraction analysis. Diffusion electron spectroscopy has been used to analyze the amount absorption of the dye on the surface of the various TNT, which acknowledges the direct co relation between the dye absorption and morphology of the sample.

Micellar and Polymer Catalysis in the Kinetics of Oxidation of L-lysine by Permanganate Ion in Perchloric Acid Medium

ABSTRACT Kinetics of oxidation of L-lysine by permanganate ion in a perchloric acid medium was investigated to explore the order of the reaction with respect to oxidant and substrate and to study the catalytic behaviour of sodium lauryl sulphate (SLS) and polyethylene glycol (PEG). The reaction was found to be first-order with respect to the oxidant and the substrate and zero-order with respect to hydrogen ion. Changes in the sodium sulphate concentration produce a non-significant variation in the rate of the reaction. SLS and PEG were found to catalyze the reaction. Surfactant catalysis was modelled by Piszkiewicz's cooperativity model, while polymer catalysis was explained with the help of the Benesi-Hildebrand equation. The temperature dependence of the rate of the reaction was elucidated, and activation parameters were obtained. Interestingly, the reaction was found to possess positive activation entropy indicating the dissociative nature of the transition state and outer-sphere electron transfer mechanism. A mechanism of the reaction that is supported by the experimental findings was suggested. Keywords: L-lysine, permanganate ion, micellar catalysis, polymer catalysis, outer sphere electron transfer mechanism.

Poređenje teorijskog i eksperimentalnog ispitivanja procesa protonacije nekih tionova u kiselim medijima

PM3 semiempirical method was used for quantum chemical investigation in order to investigate the electronic properties and to determine the protonation centre in 1,2,4-triazoline-3-thione molecule. Confirmation of protonation center in acid media of investigated compounds was made using the values of atomic charges, as well as, proton affinity values. The results from semiempirical calculations indicated that the protonation center in the thione molecule was the sulphur atom. The behavior of thiones was investigated in mineral acid media using UV spectroscopy. The influence of the strength of the acid and its anion on the protonation process was discussed using three different mineral acids (perchloric, hydrochloric and phosphoric acid) for protonation. The protonation process in perchloric and hydrochloric acid took place in one step, while in phosphoric acid was not finished even when its concentration was to the highest degree. The dissociation constants of protonated forms (pKBH + ) and the solvation parameter m* values were calculated in accordance with "excess acidity" function method (Cox and Yates) using the absorbance data from the experimental and reconstructed spectra (Characteristic Vector Analysis (CVA)). The determined pKBH + values in hydrochloric acid had more negative value than those obtained in perchloric acid media. The pKBH + values were in agreement with the literature data for this class of compounds.

Unprecedented Treatment Strategy of Aquatic Environments: Oxidative Degradation of Penicillin G by Chromium Trioxide in Acidic Media and the Impact of Metal Ion Catalysts: Kinetics and Mechanistic Insights.

Degradation kinetics and pathways of the antibiotic penicillin G (Pen) have been examined via oxidation by chromium trioxide (CrVI) in aqueous sulfuric and perchloric acid media. The oxidation reactions were monitored by spectrophotometry at 298 K. In both acidic media, penicillin G oxidation was set to proceed through acid catalysis. The stoichiometry of the reactions designated that 3 moles of Pen required 2 moles of CrVI. The kinetics of Pen oxidation in both acids was of the first order with regard to [CrVI] and less-than unity order with regard to [Pen] and [H+] in their variation. The rates of reactions displayed negligible impacts upon altering ionic strengths or dielectric constants of the reaction media. There was no intrusion of free radicals throughout the redox reactions. Addition of low concentrations of Ni2+, Cu2+, and Zn2+ ions enhanced the oxidation rates, while addition of Cr3+ as a described product did not noteworthily alter the rates. Under comparable investigational circumstances, the oxidation rates in HClO4 were almost 2-fold greater than in H2SO4. The oxidation products of penicillin G were identified by spectral analysis and spot tests as phenyl acetic acid, 2-formyl-5,5-dimethyl-thiazolidine-4-carboxlate ion, ammonium ion, and carbon dioxide. Reliance of reaction rates on temperature has been explored, and the activation and thermodynamic parameters were estimated and debated. In view of the noted reactions’ orders and products’ identification, a plausible mechanism for the oxidation reactions was suggested. The derived rate law was set to be in accordance with the acquired results. This study offers an unprecedented simple and low-cost treatment method for removal or degradation of certain pollutants for protecting the environment and human health.

Investigation of kinetics and mechanistic studies of N-(2-hydroxyethyl)phthalimide by +1 halogen oxidant in acidic medium

Abstract The oxidation of N-(2-hydroxyethyl)phthalimide (NHEP) by chloramine T (CAT) in perchloric acid medium has been investigated iodometrically at 298 K. The stoichiometry of the reaction was found to be 1:2. The oxidation products were identified by LC-MS analysis. Kinetic orders with respect to oxidant, substrate and acid concentrations were determined. Enhancement of rate observed with an increase in acid concentration. Effect of solvent polarity and ionic strength was studied. Addition of p-toluene sulfonamide (reductant) to the reaction mixture has no significant influence on the rate. The active species of the oxidant in acidic medium was ascertained. Plausible mechanistic scheme explaining all of the observed kinetic results have been proposed. The effect of temperature on the reaction rates has also been studied. Activation parameters and thermodynamic quantities were evaluated and discussed. The rate constant of the slow step of the reaction along with the equilibrium constants were also calculated.

Soluble Colloidal Manganese Dioxide: Formation, Characterization and Application in Oxidative Kinetic Study of Ciprofloxacin

Soluble colloidal manganese dioxide was formed by reduction of potassium permanganate with sodium thiosulphate in neutral aqueous medium at 25 ºC. The obtained nano-sized colloidal manganese dioxide was found to be dark reddish-brown in color and stable for several months. The formation of manganese dioxide was confirmed by UV-visible spectrophotometer and determination of oxidation state of Mn species in manganese dioxide. The effect of different concentration of sodium thiosulphate on the formation of manganese dioxide was also studied. The nano-sized colloid manganese dioxide was characterized by transmission electron microscopy and Fourier transform infrared spectrophotometer. The formed soluble colloidal manganese dioxide was used as an oxidant in oxidation of ciprofloxacin in perchloric acid medium at 35 ºC. The reaction was first-order concerning to concentration of manganese dioxide and hydrogen ion but fractional order with ciprofloxacin. The results suggest formation of complex between ciprofloxacin and manganese dioxide. The oxidation products were also identified based on stoichiometric and characterization results. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Substrate Inhibition in Ruthenium(III) Catalyzed Oxidation of Propane-1,3-diol by Periodate in Acidic Medium: A Kinetic Study

Ruthenium(III) catalyzed oxidation of propane-1,3-diol by potassium periodate was studied in aqueous perchloric acid medium. Orders of reaction with respect to concentrations of oxidant, substrate, acid and catalyst were determined. First order in oxidant and catalyst concentrations, and inverse fractional order in acid medium were observed. In addition, substrate inhibition (i.e. a decrease in reaction rate with an increase in substrate concentration) was observed. Effect of addition of salt and solvent was studied. Based on the studies of temperature variation, Arrhenius parameters were calculated. Plausible mechanism was also proposed based on observed kinetics.

UV Spectrophotometric Determination of Thermodynamic Dissociation Constants of Some Aromatic Hydrazones in Acid Media

The spectral behavior of some p-nitro-p-substituted benzoylhydrazones in the perchloric acid media was followed, applying the UV spectroscopy. The position of the absorption maximum in the spectra was defined in acidic media and the electronic transitions were discussed, as well (7&lt;pH&lt;1). The equilibrium between neutral and protonated form was investigated in the ethanol-water (V/V, 1:1) solutions. The observed changes in the UV spectra suggested that protonation process took place in one step. The pH region of protonation ranges between 1.4 and 2.9. Using the changes in the UV spectra which appear as a result of the protonation reaction the stoichiometric dissociation constants were determined numerically (pKBH+ = n·pH + logI) and graphically (intercept of the dependence of logI on pH). Thermodynamic dissociation constants were estimated as an intercept of dependence of pKBH+ on square root of the ionic strength. In order to achieve that, measurements were performed at different ionic strengths: 0.1, 0.25 and 0.5 mol/dm3, adjusted with sodium perchlorate. The obtained thermodynamic pKBH+ values ranged between 2.07 and 2.58. In order to predict proton transfer at a given pH, semiempirical methods AM1 and PM3 were applied. The influence of the substituents present in the p-position of the benzene ring on pKBH+ values of investigated hydrazones was discussed, too. Total energy, binding energy, enthalpy of formation, Gibbs energies of formation, atomic charge and proton affinity values were used to predict protonation site in hydrazone molecule. Furthermore, the stability and the proton affinity of the isomers (E and Z) in which hydrazones exist and their protonated forms were defined.