Formation of hydrates from asymmetric and cyclic ketones in their oxidation by alkaline hexacyanoferrate(III)

Abstract  Alkaline hexacyanoferrate(III) oxidizes 2-methyl-3-pentanone and 2-methylcyclohexanone quite rapidly. Kinetic data show second-order kinetics with respect to hydroxide ion concentrations indicating the formation of hydrates by ketones in aqueous alkaline medium before their reaction with the oxidant. The rate follows direct proportionality with respect to the concentrations of hexacyanoferrate(III) and ketones. Externally added hexacyanoferrate(II) does not affect the reaction velocity indicating the reduction of oxidant takes place after the rate determining step. Orders with respect to various reactants were confirmed by various methods and the overall rate constant of the reaction was calculated by three different variations. Thermodynamic data suggest that 2-methyl-3-pentanone forms the activated complex more easily compared to 2-methylcyclohexanone. Graphical abstract  Second-order in [OH⁻] in the oxidation of 2-methyl-3-pentanone and methyl cyclohexanone by alkaline hexacyanoferrate (III) indicates that oxidation proceeds through the formation of hydrates. Rate constant and thermodynamic parameters at five temperatures were calculated. Mono and dicarboxylic acids were confirmedto be the final oxidation products. Rate law given was—

Un-catalyzed oxidation of cyclic ketones by alkaline hexacyanoferrate(III) - Kinetic evidence for the formation of hydrates

Hydrate formation by cyclic ketones confirmed by kinetic and spectral studies shows reduction of hexacyanoferrate(III) after the slow step. Orders and rate constants were confirmed by various methods.     

Iridium(III) catalyzed oxidation of cyclic ketones by cerium(IV)

IrCl₃which is considered to be a sluggish catalyst in alkaline media, was found to surpass the catalytic efficiency of even osmium and ruthenium in acidic media in the oxidation of cyclopentanone and 2-methylcyclohexanone by cerium(IV) sulphate in aqueous sulphuric acid medium. It was observed that the order of the reaction shows direct proportionality with respect to low concentrations of the oxidant and alcohols, but tends to become independent of concentration at higher concentrations. On increasing the concentrations of externally added Cl^-, H⁺ and Ce^IIIions, the rate of the reaction decreases sharply initially but the decrease in rate becomes less prominent as their concentration is increased. The rate of reaction is directly proportional with respect to IrCl₃concentrations. Kinetic data suggest that the production of Ce^III ion occurs before the rate-determining step. Parameters such as the energy of activation, free energy of activation and entropy data collected at five different temperatures suggest that cyclopentanone forms the activated complex more easily.     

Kinetics of the Ru(III) catalyzed oxidation of formaldehyde and acetaldehyde by alkaline hexacyanoferrate(III)

The kinetics of ruthenium(III) catalyzed oxidation of formaldehyde and acetaldehyde by alkaline hexacyanoferrate(III) has been studied spectrophotometrically. The rate of oxidation of formaldehyde is directly proportional to [Fe(CN) _3– ⁶ ] while that of acetaldehyde is proportional tok[Fe(CN) _3– ⁶ ]/{k +k[Fe(CN) _3– ⁶ ]}, wherek, k andk are rate constants. The order of reaction in acetylaldehyde is unity while that in formaldehyde falls from 1 to 0. The rate of reaction is proportional to [Ru(III)] _T in each case. A suitable mechanism is proposed and discussed.

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Die Kinetik der Ru(III)-katalysierten Oxidation von Formaldehyd und Acetaldehyd mittels alkalischem Hexacyanoferrat(III)

Zusammenfassung Die Untersuchung der Kinetik erfolgte spektrophotometrisch. Die Geschwindigkeitskonstante der Oxidation von Formaldehyd ist direkt proportional zu [Fe(CN) _3– ⁶ ], währenddessen die entsprechende Konstante für Acetaldehyd proportional zuk[Fe(CN) _3– ⁶ ]/{k +k[Fe(CN) _3– ⁶ ]} ist, wobeik,k undk Geschwindigkeitskonstanten sind. Die Reaktionsordnung für Acetaldehyd ist eine erste, die für Formaldehyd fällt von erster bis zu nullter Ordnung. Die Geschwindigkeitskonstante ist in jedem Fall proportional zu [Ru(III)] _T . Es wird ein passender Mechanismus vorgeschlagen.

     

Ruthenium(III) catalyzed oxidation of hexacyanoferrate(II) by periodate in aqueous alkaline medium

Ruthenium(III) catalyzed oxidation of hexacyanoferrate(II) by periodate in alkaline medium is assumed to occurvia substrate-catalyst complex formation followed by the interaction of oxidant and complex in the rate-limiting stage and yield the products with regeneration of catalyst in the subsequent fast step. The reaction exhibits fractional order in hexacyanoferrate(II) and first-order unity each in oxidant and catalyst. The reaction constants involved in the mechanism are derived.     

Kinetics and mechanism of the ruthernium(III) catalyzed oxidation of propane-1,3-diol by alkaline hexacyanoferrate(III)

The kinetics of oxidation of propane-1,3-diol by alkaline hexacyanoferrate (III) catalyzed by ruthenium trichloride has been studied spectrophotometrically. A reaction mechanism involving the formation of an intermediate complex between the substrate and the catalyst is proposed. In the rate-determining step this complex is attacked by hexacyanoferate(III) forming a free radical which is further oxidized.     

Kinetic study of ruthenium(VI) -- catalyzed oxidation of 2-methoxy- ethanol by aqueous alkaline hexacyanoferrate(III)

The kinetics of ruthenium(VI) catalyzed oxidation of 2-methoxyethanol by hexacyanoferrate(III) ion in an aqueous alkaline medium at constant ionic strength shows zero order dependence on hexacyanoferrate(III) and first order dependence on Ru(VI). Dependence of substrate concentration shows a Michaelis – Menten type behaviour. The rate increases with the decrease in alkali concentration. A reaction mechanism involves the formation of an intermediate complex between the substrate and ruthenium(VI). This complex decomposes slowly, producing ruthenium(IV), which is reoxidized by hexacyanoferrate(III) in subsequent steps. The theoretical rate law obtained is in complete agreement with the experimental observations.     

Kinetics and mechanism of oxidation of quinol by alkaline hexacyanoferrate(III)

The reaction between quinol and alkaline hexacyanoferrate(III) at constant ionic strength gives p-benzoquinone. The rate of the reaction was first order in the concentrations of substrate, oxidant and alkali. The slow step of the reaction involves the formation of the p-benzosemiquinone radical, which was detected by esr spectroscopy as a five-line spectrum with peak intensity ratios of 14641.

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(III) -. , . - , , 14641.

     

Rhodium(III) NCN pincer complexes catalyzed transfer hydrogenation of ketones

Air-stable monomeric rhodium(III) NCN pincer complexes were synthesized via direct C-H bond activation of 1,3-bis(2-pyridyloxy)benzene, 3,5-bis(2-pyridyloxy)toluene and 3,5-bis(2-pyridyloxy)anisole with RhCl₃·3H₂O in ethanol under reflux. The synthesized complexes were characterized by elemental analysis and ¹H NMR. One of the complexes was structurally characterized by X-ray analysis. An investigation into the catalytic activity of the complex 1a as catalyst for transfer hydrogenation of ketones to alcohols at 82 °C in the presence of iPrOH/KOH was undertaken with the conversions up to 99%.     

Kinetic study of the ruthenium(VI)‐catalyzed oxidation of benzyl alcohol by alkaline hexacyanoferrate(III)

The kinetics of the Ru(VI)‐catalyzed oxidation of benzyl alcohol by hexacyanoferrate(III), in an alkaline medium, has been studied using a spectrophotometric technique. The initial rates method was used for the kinetic analysis. The reaction is first order in [Ru(VI)], while the order changes from one to zero for both hexacyanoferrate(III) and benzyl alcohol upon increasing their concentrations. The rate data suggest a reaction mechanism based on a catalytic cycle in which ruthenate oxidizes the substrate through formation of an intermediate complex. This complex decomposes in a reversible step to produce ruthenium(IV), which is reoxidized by hexacyanoferrate(III) in a slow step. The theoretical rate law obtained is in complete agreement with all the experimental observations. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 421–429, 2002     

Kinetic study of Ru(VI)-catalyzed oxidation of cyclic alcohols by hexacyanoferrate(III) in aqueous alkaline medium

The kinetics of the oxidation of cyclopentanol, cyclohexanol, 2? methylcyclohexanol, and cycloheptanol by hexacyanoferrate(III) ions in mild alkaline medium has been studied in the presence of traces of ruthenium(VI) ≈ 10^?7M at constant ionic strength (0.26M). The results suggest that the oxidation of the studied cyclic alcohols proceeds via the formation of a complex between Ru(VI) and the substrate which slowly decomposes, giving the reduced form of ruthenium which was reoxidized to Ru(VI) in a fast step by alkaline hexacyanoferrate(III) ions. The product study shows the production of the corresponding ketone.     

Oxidation of chromium(III) by alkaline hexacyanoferrate(III)

Alkaline hexacyanoferrate(III) oxidation of freshly prepared solutions of Cr^III (pH>12) at 27°C follows the rate law, Equation 1:

Ruthenium(VI) catalyzed oxidation of sodium salts of lactic, tartaric and glycolic acid by alkaline hexacyanoferrate(III)

The kinetics of ruthenium(VI) catalyzed oxidation of sodium salts of lactic, tartaric and glycolic acid by hexacyanoferrate(III) in aqueous alkaline medium have been studied at constant ionic strength. The reaction shows first order dependence on ruthenium(VI) and zero order on hexacyanoferrate(III). The rate of reaction increases with increasing substrate concentration and shows Michaelis-Menten type behavior. The rate of reaction decreases with increase in hydroxide ion concentration. Oxidation proceeds via formation of a complex between substrate and ruthenium(VI). A probable mechanism is suggested.

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(VI) , (III) . (VI) (III). -. . (VI). .

     

Kinetics and mechanism of the ruthenium(III)-catalysed oxidation of aminoalcohols by alkaline hexacyanoferrate(III)

Summary The kinetics of the ruthenium(III)-catalysed oxidation of aminoalcoholsviz. 2-aminoethanol and 3-aminopropanol by alkaline hexacyanoferrate(III) has been studied spectrophotometrically. The reactions are rapid initially, then follow a second order rate dependence with respect to each of the catalyst and the oxidant. The second order rate dependence with respect to ruthenium(III) was observed for the first time. The order in [Aminoalcohol] and [OH^–] is unity in each case. A suitable mechanism, consistent with the observed kinetic data is postulated.     

Kinetics and mechanism of the oxidation of butane-2,3-diol by alkaline hexacyanoferrate (III), catalyzed by ruthenium trichloride

The kinetics of oxidation of butane-2,3-diol by alkaline hexacyanoferrate (III), catalyzed by ruthenium trichloride has been studied spectrophotometrically. The reaction rate shows a zero-order dependence on oxidant, a first-order dependence on |Ru(III)|_T, a Michaelis-Menten dependence on |diol|, and a variation complicated on |OH⁻|. A reaction mechanism involving the existence of two active especies of catalyst, Ru(OH)₂⁺ and Ru(OH)₃, is proposed. Each one of the active species of catalyst forms an intermediate complex with the substrate, which disproportionates in the rate determining step. The complex disproportionation involves a hydrogen atom transfer from the α C(SINGLE BOND)H of alcohol to the oxygen of hydroxo ligand of ruthenium, to give Ru(II) and an intermediate radical which is then further oxidized. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 1–7, 1997.     

Kinetic study of ruthenium(VI)‐catalyzed oxidation of 2‐butanol by alkaline hexacyanoferrate(III)

The oxidation kinetics of 2‐butanol by alkaline hexacyanoferrate(III) catalyzed by sodium ruthenate has been studied spectrophotometrically. The initial rates method was used for kinetic analysis. The reaction rate shows a fractional‐order in [hexacyanoferrate(III)] and [substrate] and a first‐order dependence on [Ru(VI)]. The dependence on [OH⁻] is rather more complicated. The kinetic data suggest a reaction mechanism involving two active catalytic species. Each one of these species forms an intermediate complex with the substrate. The attack of these complexes by hexacyanoferrate(III), in a slow step, produces ruthenium(V) complexes which are oxidized in subsequent steps to regenerate the catalyst species. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 1–9, 1999     

Kinetics and mechanism of electron transfer reactions. Osmium(VIII) catalyzed oxidation of mannitol by hexacyanoferrate(III) in aqueous alkaline medium

The kinetics of electron transfer from mannitol to hexacyanoferrate(III), catalyzed by osmium(VIII), has been studied in alkaline medium. The substrate order is complex, whereas it is one with respect to the catalyst. The rate is independent of the concentration of oxidant. Also, the rate increases with increasing concentration of hydroxide ion in a complex manner. A kinetic rate law corresponding to the proposed mechanism has been suggested as follows:

Kinetics and mechanism of a trans-tetraazamacrocyclic chromium(III) complex oxidation by hexacyanoferrate(III) in strongly alkaline media

Oxidation of the trans-[Cr(cyca)(OH)₂]⁺ complex, where cyca = meso-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, by [Fe(CN)₆ ]^3- ion in strongly alkaline media, leading to [Cr^V O(cyca_ox )]³⁺ ion, has been studied using electronic and e.p.r. spectroscopy. The kinetics of the Cr^III → Cr^IV transformation have been studied using a large excess of the reductant and OH^- ion over the oxidant. The reaction is a second order process: first order in [Cr^III] and [Fe^III] at constant [OH^-]. The second order rate constant is higher than linearly dependent on the OH^- concentration. The mechanism of the reaction has been discussed. A relatively inert intermediate chromium(V) species was detected based on characteristic bands in the visible region and the e.p.r. signal at g_iso = 1.987 for the systems where an excess of oxidant was used. The hyperfine structure of the main e.p.r. signal is consistent with the d¹ -electron interactions with four equivalent nitrogen nuclei and [Cr^V = O(cyca_ox)]³⁺ formula, where cyca_ox = oxidized cyca, can be postulated for the intermediate Cr^V complex.     

Kinetic study of 2‐propanol and benzyl alcohol oxidation by alkaline hexacyanoferrate(III) catalyzed by a terpyridyl ruthenium complex

The complex (Trpy)RuCl₃ (Trpy = 2,2′:6′,2″‐terpyridine) reacts with alkaline hexacyanoferrate(III) to form a terpyridyl ruthenium(IV)‐oxo complex that catalyzes the oxidation of 2‐propanol and benzyl alcohol by alkaline hexacyanoferrate(III). The reaction kinetics of this catalytic oxidation have been studied photometrically. The reaction rate shows a first‐order dependence on [RU(IV)], a zero‐order dependence on [hexacyanoferrate(III)], a fractional order in [substrate], and a fractional inverse order in [HO⁻]. The kinetic data suggest a reaction mechanism in which the catalytic species and its protonated form oxidize the uncoordinated alcohol in parallel slow steps. Isotope effects, substituent effects, and product studies suggest that both species oxidize alcohol through similar pericyclic processes. The reduced catalytic intermediates react rapidly with hexacyanoferrate(III) and hydroxide to reform the unprotonated catalytic species. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 760–770, 2000