Kinetics of oxidation of pantothenic acid by chloramine‐T in perchloric acid and in alkaline medium catalyzed by OsO4: A mechanistic approach

Kinetics of oxidation of pantothenic acid (PA) by sodium N‐chloro‐p‐toluenesulfonamide or chloramine‐T (CAT) in the presence of HClO₄ and NaOH (catalyzed by OsO₄) has been investigated at 313 K. The stoichiometry and oxidation products are same in both media; however, their kinetic patterns were found to be different. In acid medium, the rate shows first‐order dependence on [CAT]_o, fractional‐order dependence on [PA]_o, and inverse fractional‐order on [H⁺]. In alkaline medium, the rate shows first‐order dependence each on [CAT]_o and [PA]_o and fractional‐order dependence on each of [OH^?] and [OsO₄]. Effects of added p‐toluenesulfonamide and halide ions, varying ionic strength, and dielectric constant of medium as well as solvent isotope on the rate of reaction have been investigated. Activation parameters were evaluated, and the reaction constants involved in the mechanisms have been computed. The proposed mechanisms and the derived rate laws are consistent with the observed kinetics. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 201–210, 2005     

Kinetics and mechanism of palladium(II) catalysed oxidation of amines and aminoalcohols by N-bromosuccinimide in perchloric acid

Summary The kinetics of oxidation of amines (EtNH₂, Et₂NH, Et₃N) and aminoalcohols [H₂NCH₂CH₂OH, H₂N(CH₂)₃OH, (CH₂CH₂OH)₂NH, (CH₂CH₂OH)₃N] by N-bromosuccinimide (NBS) have been studied in aqueous HClO₄ with PdCl₂ as catalyst, and in the presence of Hg(OAc)₂ to ensure oxidation by pure NBS. The order of reaction with respect to NBS was unity, however, an increase in [NBS]₀ resulted in a decrease in the rate constant. The rate was directly proportional to [Pd^II] for the aminoalcohols while for EtNH₂ the rate was proportional to k + k[Pd^II] (where k and k are rate constants for the uncatalysed and catalysed paths, respectively). Retarding effects for HClO₄, succinimide, Cl^– and AcOH on the rate of oxidation were observed. The kinetic data support the formation of [Pd^II-A] and [Pd^II-(A)₂] complexes (where A represents amine or aminoalcohol). A mechanism, consistent with the observed kinetic data, is proposed.     

Kinetics and mechanism of osmium (VIII) and ruthenium(III) catalyzed oxidation of aliphatic amines by chloramine-T in alkaline and perchloric acid media

The kinetics of oxidation of aliphatic amines viz., ethylamine, n-butylamine, isopropylamine (primary amines), diethylamine (secondary amine), and triethylamine (tertiary amine) by chloramine-T have been studied in NaOH medium catalyzed by osmium (VIII) and in perchloric acid medium with ruthenium(III) as catalyst. The order of reaction in [Chloramine-T] is always found to be unity. A zero order dependence of rate with respect to each [OH^?] and [Amine] has been observed during the osmium(VIII) catalyzed oxidation of diethylamine and triethylamine while a retarding effect of [OH^?] or [Amine] on the rate of oxidation is observed in case of osmium(VIII) catalyzed oxidation of primary aliphatic amines. The ruthenium(III) catalyzed oxidation of amines follow almost similar kinetics. The order of reactions in [Amine] or [Acid] decreases from unity at higher amine or acid concentrations. The rate of oxidation is proportional to {k′ and k″ [Ruthenium(III)] or [Osmium(VIII)]} where k′ and k″ (having different values in case of ruthenium(III) and osmium(VIII)) are the rate constants for uncatalyzed and catalyzed path respectively. The suitable mechanism consisting with the kinetic data is proposed in each case and discussed.     

Recovery and purification of Sr(II) in perchloric acid medium

Perchloric acid was found to be a suitable medium for the quantitative leaching of Sr(II) from homogeneous and calcined (Th,Sr)O₂ particularly with respect to the contamination from Th(IV). ⁹⁰Sr is a cause of major concern to the environment due to its long half life (28.6 years), significant abundance in large inventory of spent nuclear fuels (~350 thousand tons) awaiting geological disposal and its chemical similarity to Ca(II), an essential element for the living beings. Application of ⁹⁰Sr as a parent radionuclide for ⁹⁰Y (used in therapy radiopharmaceuticals) is possible provided it can be made available at desired high purity. In this context, the distribution coefficients of Sr(II), Th(IV), Zr(IV), Y(III), ¹⁵²Eu(III) and ¹³⁷Cs(I) were determined using Sr selective crown ether 4,4′(5′)-di-tert-butyl-dicyclohexano-18-crown-6 by solid–liquid extraction in perchloric acid medium. Feasibility of employing extraction chromatography using Sr selective resin for the recovery and purification of Sr(II) from leached perchloric acid medium was explored. Perchloric acid medium is better than nitric acid medium for the uptake of Sr by Sr selective chromatographic resin under varying loading conditions of Sr(II). Similarly pH 2 solution appears better eluent of Sr(II) than distilled water. Present work offers a novel approach for setting up a ⁹⁰Sr–⁹⁰Y generator.     

Kinetics and mechanism of oxidation of D-altrose by aqua-cerium(IV) in perchloric acid medium

Kinetics of the oxidation of D-altrose by Ce(IV) perchlorate has been studied in perchloric acid medium. At equivalent concentrations the overall order of the reaction is two, being unity in each reactant. The reaction is characterized by a primary positive kinetic salt effect. Perchloric acid has been found to enhance the rate, while the addition of the reaction products retards the rate. No evidence for initial complexation has been obtained. Thermodynamic parameters have been determined and a mechanism consistent with the observed results is proposed.

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D- Ce(IV) . , . . , . . , .

     

Kinetics of oxidation of methanol and mono-deutero-methanol by chromium(VI) in perchloric acid medium

Kinetics of the oxidation of methanol and mono-deutero-methanol by Cr(VI) over a wide range of temperature (25–40°) have been studied in perchloric acid medium at constant ionic strength (μ = 1.0 M) adjusted with sodium perchlorate. Each reaction is first order with respect to the substrate and dichromate concentrations but the order with respect to [H⁺] is nearly 3 in each case. Both these reactions take place at almost the same rate under identical experimental conditions. The activation parameters of the reactions are not widely different and the values of ΔH3 and ΔS3 for the oxidation of methanol are 79.5 kJ mole ^-1 and - 38.1 J deg^-1 mole^-1 respectively, whereas the corresponding values for the deuterated compound are 83.8 kJ mole^-1 and -23.9 J deg^-1 mole^-1. The probable mechanism of the reactions is discussed.     

Kinetics of oxidation of ethanol by potassium permanganate in perchloric acid medium

The oxidation of ethanol by permanganate has been found to obey the rate law v=k[MeCHO][MnO ₄ ^– ][H⁺]. The results are compared with those found for chromium (VI) oxidation of the same substrate.

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V=k[MeCHO][MnO ₄ ^– ][H⁺]. , (VI).

     

Palladium(II) acetate‐catalyzed reduction of imines to the corresponding amines by triethylsilane

Reduction of a variety of imine compounds with triethylsilane in the presence of catalytic amounts of palladium(II) acetate in ethanol resulted in the formation of the corresponding amines in excellent yields after short reaction times. Copyright © 2013 John Wiley & Sons, Ltd.     

Binding of hexacyanoferrate(II) by aliphatic amines in aqueous solution

The stability of hexacyanoferrate(II)-amine(methylamine, ethylenediamine, diethylenetriamine and tetraethylenepentamine) was determined potentiometrically. Species Fe(CN)₆(A)H _j ^(j–4) (A=amine) are formed in all the systems investigated, with j=1...n+2 (n=number of aminogroups). Some other complexes Fe(CN)₆(A)_iH_j (with i>1) were also found. The stability of these complexes is fairly high: the full protonated amine species, show for the reaction Fe(CN)₆ ^4- + H_nAⁿ⁺ = Fe(CN)₆(A)H_n ^(n-4) an equilibrium constant given by logK=0.686+2.10n. Factors affecting the stability are discussed in comparison with similar systems, together with the importance of interferences.     

Methanol and ethanol oxidation by chromium(VI) in aqueous perchloric acid

Summary Oxidation of short-chain alcohols (MeOH and EtOH) by Cr^VI in concentrated aqueous HClO₄ does not fit pseudo-first order rate equations, but results can be expressed in a two-exponential equation. A reaction mechanism based upon a chromate ester intermediate in equilibrium with the protonated alcohol and the chromic acid, suitable for a longer chain alcohol, does not account for kinetic results. A new mechanism is considered involving an intermediate reaction between chromic and perchloric acids.     

Iron(II)-Induced oxidation of hypophosphite by peroxydiphosphate in acid medium

It is shown that when peroxydiphosphate reacts with excess of iron(II) an induced oxidation of hypophosphite occurs if any is present.     

Antagonism in (conventional anionic–gemini anionic) mixed micelle catalyzed oxidation of D‐fructose by alkaline chloramine‐T: A kinetic study

The catalytic effect of individual conventional anionic surfactant, namely, sodium lauryl sulfate (NaLS), anionic gemini surfactant, namely, sodium salt of bis(1‐dodecenyl succinamic acid) (NaBDS), and mixed surfactant (NaLS + NaBDS) on the rate of oxidation of D ‐fructose by alkaline chloramine‐T has been investigated. The reaction always showed a first‐order dependence of rate with respect to each fructose, alkali, and chloramine‐T. The rate was proportional to (k′+k″ [surfactant]), where k′ and k″ are the rate constants in the absence and presence of the surfactant, respectively. The binding parameters have been evaluated. The observed catalytic effect of mixed micelle on the rate of oxidation was always less than the algebraic sum of the catalytic effect of two surfactants when they were taken separately, suggesting an antagonism (negative synergism) in mixed micelle. The antagonism has also been confirmed by determining critical micelle concentration and interaction parameter (β^m) of mixed micelle under the experimental conditions of kinetics, that is, in alkaline medium. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 123–132, 2009     

Palladium(II) complexes with 1-hydroxyethylidene-1,1-diphosphonic acid

Complex formation in a K₂PdCl₄-HEDP system (HEDP is 1-hydroxyethylidene-1,1-diphosphonic acid) at the metal-to-ligand ratios 1 : 1 and 1 : 2 is studied by ³¹P and ¹H NMR spectroscopy. The formation of equimolar complexes, in which HEDP is coordinated to palladium(II) in a bidentate mode through two oxygen atoms of the phosphonic groups, is found in these systems. The structure and charge characteristics of conformers of the complexes are simulated by the quantum-chemical methods.     

A kinetic and mechanistic study of the oxidation of tyrosine by chromium(VI) in aqueous perchloric acid medium

The oxidation of tyrosine by chromium(VI) in aqueous perchloric acid medium has been studied spectrophotometrically at 30 °C and at a constant ionic strength I = 3.10 mol dm⁻³. The main reaction products were identified as chromium(III) and 4-hydroxyphenylacetaldehyde. The stoichiometry is 2:3, i.e., two moles of chromium(VI) react with three moles of tyrosine. The reaction is first order with respect to both chromium(VI) and tyrosine. Increase in perchloric acid concentration increased the rate of reaction. The order with respect to acid concentration was found to be two. Added products, ionic strength and dielectric constant of the medium did not have any significant effect on the reaction rate. A suitable mechanism is proposed. The activation parameters were determined with respect to the slow step of the mechanism. The thermodynamic quantities were also determined and discussed.     

Kinetic and mechanistic studies of some aliphatic amines' oxidation by sodium N‐bromo‐p‐toluenesulfonamide in hydrochloric acid medium

Oxidations of n‐propyl, n‐butyl, isobutyl, and isoamyl amines by bromamine‐T (BAT) in HCl medium have been kinetically studied at 30°C. The reaction rate shows a first‐order dependence on [BAT], a fractional‐order dependence on [amine], and an inverse fractional‐order dependence on [HCl]. The additions of halide ions and the reduction product of BAT, p‐toluenesulfonamide, have no effect on the reaction rate. The variation of ionic strength of the medium has no influence on the reaction. Activation parameters have been evaluated from the Arrhenius and Eyring plots. Mechanisms consistent with the preceding kinetic data have been proposed. The protonation constant of monobromamine‐T has been evaluated to be 48 ± 1. A Taft linear free‐energy relationship is observed for the reaction with ρ* = −12.6, indicating that the electron‐donating groups enhance the reaction rate. An isokinetic relationship is observed with β = 350 K, indicating that enthalpy factors control the reaction rate. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 776–783, 2000     

Palladium(II) complexes of ketimines

Summary New Pd^II complexes of biologically active ketimines containing the donor set have been synthesized and characterized by elemental analyses, molecular weight determinations and conductivity measurements. The i.r. and ¹H-n.m.r. spectra indicate a square planar structure for the complexes in which the ligand is monobasic bidentate with oxygen and azomethine nitrogen coordinating sites. Representative ketimines and their respective metal complexes were found to exhibit antimicrobial properties.Author to whom all correspondence should be directed.     

Kinetics and mechanism of oxidation of glycine by iron(iii)-1,10-phenanthroline complex in perchloric acid medium

Kinetics and mechanism of oxidation of glycine by iron (III)-1,10-phenanthroline complex has been studied in perchloric acid medium. The reaction is first order with respect to iron(III) and glycine. An increase in (phenanthroline) increases the rate, while increase in [H⁺] decreases the rate. Hence it can be inferred that the reactive species of the substrate is the zwitterionic form and that of the oxidant is [Fe(phen)₂(H₂O)₂]³⁺. The proposed mechanism leads to the rate law as elucidated.     

Kinetics and mechanism of oxidation of some aliphatic amines by ditelluratocuprate(III)

The kinetics of oxidation of some primary, secondary and tertiary aliphatic amines by ditelluratocuprate(III) was studied in alkaline medium. The order in both substrate and oxidant was found to be unity each. The reaction rate decreased with increase in ionic strength. The order of reactivity of amines was found to be secondary > primary > tertiary. A mechanism was proposed involving an adduct formation between amine and monotelluratocuprate(III), which dissociates further in a slow step followed by fast steps to give required products. TheTaft linear free energy relationship was shown to be applicable which also supports the proposed mechanism.

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Kinetik und Mechanismus der Oxidation einiger aliphatischer Amine mit Kupfer(III)-ditellurat

Zusammenfassung Die Kinetik der Oxidation einiger primärer, sekundärer und tertiärer aliphatischer Amine mit Kupfer(III)-ditellurat wurde in alkalischem Medium untersucht. Die Reaktion war jeweils erster Ordnung bezüglich Substrat und Oxidationsmittel. Die Reaktionsgeschwindigkeit nahm mit zunehmender Ionenstärke ab. Die Reaktivität stieg in der Reihenfolge sekundäre > primäre > tertiäre Amine an. Ein Mechanismus, der die Bildung eines Adduktes zwischen Amin und Kupfer(III)-monotellurat beinhaltet, wird vorgeschlagen. Dieses Addukt dissoziiert in einem langsamen Schritt, gefolgt von schnellen Schritten, in denen die gefundenen Produkte gebildet werden. Die Anwendbarkeit derTaft-Beziehung wurde getestet und unterstützt den vorgeschlagenen Mechanismus.

     

Kinetics and mechanism of oxidation of ethanol,isopropanol and benzyl alcohol by chromium(VI) in perchloric acid medium

Chromium(VI) oxidation of some alkanols has been studied in perchloric acid medium. The reactions are first order with respect to [substrate] and [HCrO₄^-]. The order with respect to [H⁺]is between 1 and 2 for all the reactions. The activation parameters of the reactions have been calculated. A mechanism consistent with the above facts has been suggested. An attempt has been made to correlate the rate of the reactions with the structure of the substrates.