Efficient oxidation of secondary alcohols to Ketones by NaOCl catalyzed by Salen-Mn(III)/NBS

An efficient catalytic system salen-Mn(III)/NBS for oxidation of secondary alcohols to ketones by inexpensive and readily available oxidizing agent NaOCl has been developed. The process resulted in good to excellent yields under the action of 2 mol % of salen-Mn(III) and 13 mol % of NBS at room temperature. However, such system was not efficient in oxidation of secondary benzyl alcohols with a strong electronicdonating substituent attached to the benzene ring due to bromination of the alcohols.     

Ru(III)-catalyzed oxidation of pyruvic acid by iodate -A kinetic study

Ru(III) acts as a catalyst in the oxidative decarboxylation of pyruvic acid by iodate. The reaction is found to be first order with respect to [oxidant] and [catalyst] and fractional order in [pyruvic acid]. Increase in the concentration of H₂SO₄ and decrease in the dielectric constant of the medium retard the oxidation process. The product of oxidation is acetic acid. A mechanism involving the formation of a complex between the substrate and the catalyst, which reacts with the oxidant in the slow step is proposed. The formation constant of the complex and the rate constant of the slow step are determined. This revised version was published online in June 2006 with corrections to the Cover Date.     

Ru(III) catalysis in the oxidation of arenes by periodate. A kinetic study

The title reactions are zero order in periodate and first order in Ru(III). All substrates show a first order dependence except for p-xylene and fluorene which follow a Michaelis-Menten behavior. The Hammett plot gives a values of-2.0. A mechanism involving metal arene -interaction is discussed.

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Ru(III). , - , -. =–2,0. . , -- .

     

Enantioselective oxidation of racemic secondary alcohols catalyzed by chiral Mn(III)-salen complexes with N-bromosuccinimide as a powerful oxidant

We demonstrate an efficient enantioselective oxidation of secondary alcohols catalyzed by Mn(III)-salen complex using N-bromosuccinimide (NBS) as the oxidant. The new protocol is very efficient for the oxidative kinetic resolution of a variety of secondary alcohols, including ortho-substituted benzylic alcohols.     

Efficient solvent-free iron (III) catalyzed oxidation of alcohols by hydrogen peroxide

Selective oxidation of secondary and benzylic alcohols was efficiently accomplished by H₂O₂ under solvent-free condition catalyzed by FeBr₃. Secondary alcohols are selectively oxidized even in the presence of primary ones. This method is high yielding, safe and operationally simple.     

Oxidation of secondary alcohols byN-methylmorpholine-N-oxide (NMO) catalyzed by Ru(II) halosulfoxide complexes. A kinetic study

RuX₂(DMSO)₄ (X=Cl,cis; Br,trans) undergoes ligand substitution in N,N-dimethylformamide (DMF) to give RuX₂(DMSO)₃DMF, which catalyzes the oxidation of secondary alcohols by NMO to ketones. Kinetics of the reaction catalyzed bytrans-RuBr₂(DMSO)₄ differed from that ofcis-RuCl₂(DMSO)₄. A mechanism is proposed involving the formation of Ru(IV)oxo species as the active intermediate and a rate expression is derived.     

Mechanism of oxidation of some aliphatic ketones by N-bromosuccinimide in acidic media

Kinetics of the oxidation of methyl n-propyl ketone and methyl isobutyl ketone by N-bromosuccinimide (NBS) have been studied in perchloric acid media in presence of mercuric acetate. A zero order dependence to N-bromosuccinimide and a first order dependence to both ketones and hydrogen ion concentrations have been observed. Sodium perchlorate, mercuric acetate and succinimide additions have negligible effect while methanol addition has a positive effect on the reaction rate. A solvent isotope effect (k₀D₂O/K₀H₂O = 2.3-2.7 and 2.4-2.8 for MeCOn.pr and MeCoi-Bu, respectively) has been observed at 35°. Kinetic investigations have revealed that the order of reactivity is methyl n-propyl ketone > methyl isobutyl ketone. Various thermodynamic parameters have been computed and corresponding 1,2-diketones were found to be the products. A suitable mechanism in conformity with the above observations has been proposed.     

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.

     

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.     

Kinetics and mechanism of Ru(III)-catalyzed oxidation of aliphatic alcohols by trichloroisocyanuric acid in HClO4 medium

The kinetics and mechanism of Ru(III)-catalyzed oxidation of some aliphatic alcohols by trichloroisocyanuric acid (TCICA) has been studied in aqueous HOAc-HClO₄ medium. The reaction is zero order in [TCICA], fractional order in [alcohol] and first order in [Ru(III)]. The reaction is insensitive towards changes in acid concentration. The rate is not affected by an increase in [Cl⁻]. The polar reaction constant (ρ*) was found to be −1.27 at 308 K. A mechanism involving complex formation between the substrate and catalyst in the fast equilibrium step followed by its decomposition in a slow step is proposed.     

TI(III) oxidation of alkenes and alkynes and Ru(III) catalysis in the oxidation of alkenes: A kinetic and mechanistic study

The oxidation of trans-stilbene, phenylacetylene, and diphenylacetylene by Tl(OAc)₃ in aqueous acetic acid medium in the presence of HClO₄ follows the rate law in [H⁺] of 0.1–1.0M, the [H⁺] dependence below 0.1M being marginal. The reactions are strongly dielectric dependent. The order of reactivity among the substrates is styrene > phenylacetylene and trans-stilbene > diphenylacetylene. A mechanism involving the oxythallation adduct by the Tl⁺(OAc)₂ species has been discussed. The use of Ru(III) as a homogeneous catalyst brings a change in the kinetic orders for trans-stilbene, the rate law being The formation constants K for the Ru(III)–alkene π complex at 40, 50, and 60°C are 90.14M^?1, 105.2M^?1, and 127.7M^?1, respectively. Interestingly the oxidation of phenylacetylene and diphenylacetylene does not undergo catalysis by Ru(III). The mechanism involving the metal–arene π complex is discussed.     

Effective oxidation of benzylic and aliphatic alcohols with hydrogen peroxide catalyzed by a manganese(III) Schiff-base complex under solvent-free conditions

A variety of alcohols were oxidized efficiently into the corresponding ketones and carboxylic acids in excellent yields with hydrogen peroxide using a manganese(III) Schiff-base complex as a catalyst under solvent-free and mild conditions. The oxidation procedure is very simple and the products are easily isolated in excellent yields.     

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.

     

Ruthenium (III)-Schiff base complex catalyzed oxidation of secondary alcohols by N-methylmorpholine-N-oxide or thallium (III) acetate

The Ru(III) Schiff base complex [Ru(L)Cl₂]Cl; L = bis(picolinaldehyde) o-phenylenediimine, catalyzes the oxidation of secondary alcohols by N-methylmorpholine-N-oxide(NMO) or thallium(III) acetate as oxidant. Kinetic studies showed the formation of Ru(V) species as the active intermediate. © 1996 John Wiley & Sons, Inc.     

Ru(III) catalysis in N-bromoacetamide oxidation of ethylene glycol and glycerol: A kinetic and mechanistic study

Kinetics of oxidation of ethylene glycol and glycerol by acidic solution of N-bromoacetamide (NBA) in the presence of ruthenium (III) chloride as a homogeneous catalyst and mercuric acetate as scavenger in the temperature range of 30–50°C have been reported. The reactions follow identical kinetics, being zero-order in substrate and first-order in Ru(III). First order dependence of the reaction on NBA at its low concentrations tends to zero order in the higher concentration range. Positive effect of [H^?] and [Cl^?] has been observed. A negative effect of acetamide and ionic strength of the medium is observed while D₂O and mercuric acetate show zero effect on the reaction velocity. Various activation parameters have been computed. The main product of the oxidation is corresponding acid. (H₂OBr)⁺ has been postulated as the oxidizing species. A suitable mechanism in conformity with the kinetic data has been proposed.     

Kinetic studies of the oxidation of chromium(III) by N-bromosuccinimide

Summary A kinetic study of the oxidation of chromium(III) by N-bromosuccinimide (NBS) in aqueous solutions and H₂O-MeOH solvent mixtures were performed. The kinetics in aqueous solutions obeyed the rate law: d[Cr^VI]/dt = {k ₄ K _h K ₂[NBS][Cr^III]_T}/[₊]{1 + K _h/[H⁺] + (K ₁ + K _h K ₂/[H⁺][NBS])} where K _h, K ₁ and K ₂ are the hydrolysis constant of [Cr^III(H₂O)₆]³⁺, and pre-equilibrium formation constants for the protonated and deprotonated precursor complexes, respectively. An innersphere mechanism is proposed. An argument based on isokinetic correlations among activation parameters for the oxidation of a series of cobalt(II) and chromium(III) complexes including [Cr(H₂O)₆]³⁺ is presented in support of a common mechanism for these reactions. Abstracted from the Ph.D. Thesis (Ain Shams University) of A. E.-D. M. Abdel-Hady.     

Kinetics of oxidation of some aliphatic ketones by ditelluratocuprate(III) in alkaline medium

The kinetics of oxidation of some ketones by ditelluratocuprate(III) were followed spectrophotometrically by estimating the disappearence of potassium ditelluratocuprate(III). The reaction follows first order kinetics in both substrates and oxidant. A correlation is found between the order of reactivity and partial rates of enolization of these ketones. By assuming that the mechanism of oxidation involves the enol form of the ketone in a slow step, the observed order of reactivity of these ketones is explained.

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(III) , (III). , , . . , , .

     

Kinetics and mechanism of oxidation of (ethylenediaminediacetato)chromium(III) by N-bromosuccinimide

The kinetics of oxidation of (ethylenediaminediacetato)-chromium(III), [Cr(EDDA)(OH2)2]+, by N-bromosuccinimide (NBS) in aqueous solution to yield CrVI have been studied spectrophotometrically over the 20–40°C range. The reaction rate is first order with respect to both [NBS] and [CrIII], and increases with pH over the range 4.8–5.8. The activation parameters were calculated. A mechanism in which deprotonated [CrIII(EDDA)(OH2)(OH)] is the reactive species is suggested. The electron transfer may proceed via an inner sphere mechanism through bridging of the two reactants by the hydroxo ligand.     

Ruthenium(III) catalyzed oxidation of sulfanilic acid by diperiodatocuprate(III) in aqueous alkaline medium. A kinetic and mechanistic approach

The kinetics of ruthenium(III) catalyzed oxidation of sulfanilic acid by diperiodatocuprate(III) (DPC) in alkaline medium at a constant ionic strength of (0.50 mol dm⁻³) has been studied spectrophoto-metrically. The reaction between sulfanilic acid and DPC in alkaline medium exhibits 1: 4 stoichiometry (sulfanilic acid: DPC). The reaction is first order with respect to [DPC] and [Ru^III] and has less than unit order both in [sulfanilic acid] and [alkali]. The active species of catalyst and oxidant have been identified. Intervention of free radicals was observed in the reaction. The main products were identified by spot test and IR. Probable mechanism is proposed and discussed. The reaction constants involved in the different steps of the mechanism are calculated. The activation parameters with respect to the slow step of the mechanism are computed and discussed. Thermodynamic quantities are also determined.