- A new binuclear oxovanadium(v) complex as a catalyst in combination with pyrazinecarboxylic acid (PCA) for efficient alkane oxygenation by H 2O2
-
A new binuclear oxovanadium(v) complex [{VO(OEt)(EtOH)}2L] (1) where H4L is bis(2-hydroxybenzylidene)terephthalohydrazide has been synthesized and fully characterized. The combination of 1 with pyrazine-2-carboxylic acid (PCA; a cocatalyst) affords a catalytic system for the efficient oxidation of saturated hydrocarbons, RH, with hydrogen peroxide and air in acetonitrile solution at 50°C to produce alkyl hydroperoxides, ROOH, as the main primary products. Very high turnover numbers (TONs) have been attained in this reaction: for example, after 2220 min, TON = 44 000 and initial TOF (turnover frequency) = 3300 h-1 per molecule of complex 1. The estimated activation energy of the cyclohexane oxygenation in the presence of 1/PCA is Ea = 16 ± 2 kcal mol-1. This value is identical to that obtained for the cyclohexane oxidation with H 2O2 catalyzed by the (n-Bu4N)[VO 3]/PCA combination (17 ± 2 kcal mol-1). The dependences of initial oxidation rates W0 on the initial concentrations of all components of the reaction mixture have been determined. Based on these kinetic data and on the regio- and bond-selectivity parameters measured in the oxidation of linear and branched alkanes a mechanism of the oxidation has been proposed which includes the generation of hydroxyl radicals in the crucial stage. The Royal Society of Chemistry.
- Sutradhar, Manas,Shvydkiy, Nikita V.,Guedes Da Silva, M. Fátima C.,Kirillova, Marina V.,Kozlov, Yuriy N.,Pombeiro, Armando J. L.,Shul'Pin, Georgiy B.
-
supporting information
p. 11791 - 11803
(2013/09/02)
-
- Branching ratios for the reaction of selected carbonyl-containing peroxy radicals with hydroperoxy radicals
-
An important chemical sink for organic peroxy radicals (RO2) in the troposphere is reaction with hydroperoxy radicals (HO2). Although this reaction is typically assumed to form hydroperoxides as the major products (R1a), acetyl peroxy radicals and acetonyl peroxy radicals have been shown to undergo other reactions (R1b) and (R1c) with substantial branching ratios: RO2 + HO2 → ROOH + O2 (R1a), RO 2 + HO2 → ROH + O3 (R1b), RO2 + HO2 → RO + OH + O2 (R1c). Theoretical work suggests that reactions (R1b) and (R1c) may be a general feature of acyl peroxy and α-carbonyl peroxy radicals. In this work, branching ratios for R1a-R1c were derived for six carbonyl-containing peroxy radicals: C2H 5C(O)O2, C3H7C(O)O2, CH3C(O)CH2O2, CH3C(O)CH(O 2)CH3, CH2ClCH(O2)C(O)CH 3, and CH2ClC(CH3)(O2)CHO. Branching ratios for reactions of Cl-atoms with butanal, butanone, methacrolein, and methyl vinyl ketone were also measured as a part of this work. Product yields were determined using a combination of long path Fourier transform infrared spectroscopy, high performance liquid chromatography with fluorescence detection, gas chromatography with flame ionization detection, and gas chromatography-mass spectrometry. The following branching ratios were determined: C2H5C(O)O2, YR1a = 0.35 ± 0.1, YR1b = 0.25 ± 0.1, and YR1c = 0.4 ± 0.1; C3H7C(O)O2, YR1a = 0.24 ± 0.15, YR1b = 0.29 ± 0.1, and YR1c = 0.47 ± 0.15; CH3C(O)CH2O2, Y R1a = 0.75 ± 0.13, YR1b = 0, and YR1c = 0.25 ± 0.13; CH3C(O)CH(O2)CH3, Y R1a = 0.42 ± 0.1, YR1b = 0, and YR1c = 0.58 ± 0.1; CH2ClC(CH3)(O2)CHO, Y R1a = 0.2 ± 0.2, YR1b = 0, and YR1c = 0.8 ± 0.2; and CH2ClCH(O2)C(O)CH3, YR1a = 0.2 ± 0.1, YR1b = 0, and YR1c = 0.8 ± 0.2. The results give insights into possible mechanisms for cycling of OH radicals in the atmosphere.
- Hasson, Alam S.,Tyndall, Geoffrey S.,Orlando, John J.,Singh, Sukhdeep,Hernandez, Samuel Q.,Campbell, Sean,Ibarra, Yesenia
-
experimental part
p. 6264 - 6281
(2012/08/28)
-
- Hydrogen peroxide oxygenation of alkanes including methane and ethane catalyzed by iron complexes in acetonitrile
-
This paper describes an investigation of the alkane oxidation with hydrogen peroxide in acetonitrile catalyzed by iron(III) perchlorate (1), iron(III) chloride (2), iron(III) acetate (3) and a binuclear iron(III) complex with 1,4,7-triazacyclononane (4). The corresponding alkyl hydroperoxides are the main products. Nevertheless in the kinetic study of cyclohexane oxidation, the concentrations of oxygenates (cyclohexanone and cyclohexanol) were measured after reduction of the reaction solution with triphenylphosphine (which converts the cyclohexyl hydroperoxide to the cyclohexanol). Methane and ethane can be also oxidized with TONs up to 30 and 70, respectively. Chloride anions added to the oxidation solution with 1 activate the perchlorate iron derivative in acetonitrile, whereas the water as additive inactivates 2 in the H 2O2 decomposition process. Pyrazine-2-carboxylic acid (PCA) added to the reaction mixture decreases the oxidation rate if 1 or 2 are used as catalysts, whereas compounds 3 and 4 are active as catalysts only in the presence of small amount of PCA. The investigation of kinetics and selectivities of the oxidations demonstrated that the mechanisms of the reactions are different. Thus, in the oxidations catalyzed by the 1, 3+PCA and 4+ PCA systems the main oxidizing species is hydroxyl radical, and the oxidation in the presence of 2 as a catalyst has been assumed to proceed (partially) with the formation of ferryl ion, (FeIV=O)2+. In the oxidation catalyzed by the 4+PCA system (TONs attain 240) hydroxyl radicals were generated in the rate-determining step of monomolecular decomposition of the iron diperoxo adduct containing one PCA molecule. A kinetic model of the process which satisfactorily describes the whole set of experimental data was suggested. The constants of supposed equilibriums and the rate constant for the decomposition of the iron diperoxo adduct with PCA were estimated.
- Shul'pin, Georgiy B.,Nizova, Galina V.,Kozlov, Yuriy N.,Cuervo, Laura Gonzalez,Su?ss-Fink, Georg
-
p. 317 - 332
(2007/10/03)
-
- Oxidations by the system 'hydrogen peroxide-manganese(IV) complex- acetic acid' - Part II: Hydroperoxidation and hydroxylation of alkanes in acetonitrile
-
Higher alkanes (cyclohexane, n-pentane, n-heptane, methylbutane, 2- and 3-methylpentanes, 3-methylhexane, cis- and trans-decalins) are oxidized at 20 °C by H2O2 in air in acetonitrile (or nitromethane) solution in the presence of the manganese(IV) salt [L2Mn2O3](PF6)2 (L = 1,4,7-trimethyl- 1,4-7-triazacyclononane) as the catalyst. An obligatory component of the reaction mixture is acetic acid. Turnover numbers attain 3300 after 2 h, the yield of oxygenated products is 46% based on the alkane. The oxidation affords initially the corresponding alkyl hydroperoxide as the predominant product, however later these compounds decompose to produce the corresponding ketones and alcohols. Regio- and bond selectivities of the reaction are high: C(1): C(2): C(3): C(4) ? 1: 40: 35: 35 and 1°: 2°: 3°is 1: (15-40): (180-300). The reaction with both isomers of decalin gives (after treatment with PPh3) alcohols hydroxylated in the tertiary positions with the cis/trans ratio of ~2 in the case of cis-decalin, and of ~30 in the case of trans-decalin (i.e. in the latter case the reaction is stereospecific). Light alkanes (methane, ethane, propane, normal butane and isobutane) can be also easily oxidized by the same reagent in acetonitrile solution, the conditions being very mild: low pressure (1-7 bar of the alkane) and low temperature (- 22 to +27°C). Catalyst turnover numbers attain 3100, the yield of oxygenated products is 22% based on the alkane. The yields of oxygenates are higher at low temperatures. The ratio of products formed (hydroperoxide: ketone: alcohol) depends very strongly on the conditions of the reaction and especially on the catalyst concentration (at higher catalyst concentration the ketone is predominantly produced).
- Shul'pin, Georgiy B.,Suess-Fink, Georg,Lindsay Smith, John R.
-
p. 5345 - 5358
(2007/10/03)
-
- Syntheses, structures, and reactivities of Cobalt(III)-alkylperoxo complexes and their role in stoichiometric and catalytic oxidation of hydrocarbons
-
Although Co(III)-alkyl peroxo species have often been implicated as intermediates in industrial oxidation of hydrocarbons with cobalt catalysts, examples of discrete [LCo(III)-OOR] complexes and studies on their oxidizing capacities have been scarce. In this work, twelve such complexes with two different ligands, L, and various primary, secondary, and tertiary R groups have been synthesized, and seven of them have been characterized by X-ray crystallography. The dianion (L2-) of the two ligands N,N-bis[2-(2- pyridyl)ethyl]-pyridine-2,6-dicarboxamide (Py3PH2, 1) and N-N-bis[2-(1- pyrazolyl)ethyl]pyridine-2,6-dicarboxamide (PyPz2-PH2, 2) bind Co(III) centers in pentadentate fashion with two deprotonated carboxamido nitrogens in addition to three pyridine or one pyridine and two pyrazole nitrogens to afford complexes of the type [LCo(III)(H2O)] and [LCo(III)(OH)]. Reactions of the [LCo(III)(OH)] complexes with ROOH in aprotic solvents of low polarity readily afford the [LCo(III)-OOR] complexes in high yields. This report includes syntheses of [Co(Py3P)(OOR)] complexes with R = (t)Bu (7, (t)Bu) = CMe3), Cm (8, Cm = CMe2Ph), CMe2CH2Ph (9), Cy (10, Cy = c-C6H11), (i)Pr (11, (i)Pr = CHMe2) or (n)Pr (12, (n)Pr = CH2CH2CH3), and [Co(PyPz2P)(OOR) complexes with R = (t)Bu (13), Cm (14), CMe2CH2Ph (15), Cy (16), (i)Pr (17) or (n)Pr (18). The structures of 8-12 and 16 have been established by X-ray crystallography. Complexes 10 and 16 are the first examples of structurally characterized compounds containing the [Co-OOCy] unit, proposed as a key intermediate in cobalt-catalyzed oxidation of cyclohexane. The metric parameters of 7-12 and 16 have been compared with those of other reported [LCo(III)-OOR] complexes. When these [LCo(III)-OOR] complexes are warmed (60-80 °C) in dichloromethane in the presence of cyclohexane (CyH), cyclohexanol (CyOH) and cyclohexanone (CyO) are obtained in good yields. Studies on such reactions (referred to as stoichiometric oxidations) indicate that homolysis of the O-O bond in the [LCo(III)-OOR] complexes generates RO· radicals, in the reaction mixtures which are the actual agents for alkane oxidation. [LCo-O·], the other product of homolysis, does not promote any oxidation. A mechanism for alkane oxidation by [LCo(III)-OOR] complexes has been proposed on the basis of the kinetic isotope effect (KIE) value (5 at 80 °C), the requirement of dioxygen for oxidation, the dependence of yields on the stability of the RO· radicals, and the distribution of products with different substrates. Both L and R modulate the capacity for alkane oxidation of the [LCo(III)-OOR] complexes. The extent of oxidation is noticeably higher in solvents of low polarity, while the presence of water invariably lowers the yields of the oxidized products. Since [LCo(III)-OOR] complexes are converted into the [LCo(III)(OH)] complexes at the end of single turnover in stoichiometric oxidation reactions, it is possible to convert these systems into catalytic ones by the addition of excess ROOH to the reaction mixtures. The catalytic oxidation reactions proceed at respectable speed at moderate temperatures and involve [LCo(III)-OOR] species as a key intermediate. Turnover numbers over 100 and ~10% conversion of CyH to CyOH and CyO within 4 h have been noted in most catalytic oxidations. The same catalyst can be used for the oxidation of many substrates. The results of the present work indicate that [LCo(III)- OOR] complexes can promote oxidation of hydrocarbons under mild conditions and are viable intermediates in the catalytic oxidation of hydrocarbons with ROOH in the presence of cobalt catalysts.
- Chavez, Ferman A.,Rowland, John M.,Olmstead, Marilyn M.,Mascharak, Pradip K.
-
p. 9015 - 9027
(2007/10/03)
-
- Oxidations by the reagent 'O2-H2O2-vanadium complex-pyrazine-2-carboxylic acid' - VIII. Efficient oxygenation of methane and other lower alkanes in acetonitrile
-
Methane, ethane, propane, n-butane and isobutane can be readily oxidized in acetonitrile solution by air and H2O2 at 20-75°C using the catalytic system [n-Bu4N]VO3/pyrazine-2-carboxylic acid, Apart from alkyl hydroperoxides which are the primary oxidation products, more stable derivatives (alcohols, aldehydes or ketones and carboxylic acids) are obtained with high total turnover numbers (e.g., at 75°C after 4 h: 420 for methane and 2130 for ethane). It was shown in the case of ethane and cyclohexane that alkanes do not yield oxygenated products in the absence of air. The cyclohexane oxidation under an 18O2 atmosphere showed a high degree of 18O incorporation into the oxygenated products. Thus in the oxidation reaction described here H2O2 is only the promoter while O2 is the 'true' oxidant.
- Nizova, Galina V.,Suess-Fink, Georg,Shul'pin, Georgiy B.
-
p. 3603 - 3614
(2007/10/03)
-
- Identification of an unexpected peroxide formed by successive isomerization reactions of the n-butoxy radical in oxygen
-
A previously unreported peroxide, C4H8O3 (5), has been identified and its mechanism of formation proposed. It is generated by two successive isomerization reactions of n-C4H9O radicals in O2. These radicals are produced by di-n-C4H9O-OC4H9 pyrolysis at 480 K in a wall-passivated quartz vessel. The peroxide is collected, among other end-products, on a liquid-nitrogen trap and recovered in liquid acetonitrile. Analysis was carried out by GC-MS, GC-MS-MS [electron impact (EI) and NH3 (or ND3)-chemical ionization (CI) conditions] and GC-FTIR. After micropreparative GC separation of the titled peroxide, 1H NMR and high-resolution EIMS were also obtained. The compound was identified as 3α-hydroxy-1,2-dioxane. The hydroperoxybutyraldehyde OHC-(CH2)2-CH2O2H is proposed to be initially formed in the gas phase and to be in equilibrium with its cyclic form (six-membered ring peroxide), by far predominant in the liquid phase at room temperature. The implications of this hydroperoxybutyraldehyde in atmospheric pollution (due to the peroxide producing capability of radicals) and in combustion are discussed.
- Jorand, Francois,Heiss, Adolphe,Sahetchian, Krikor,Kerhoas, Lucien,Einhorn, Jacques
-
p. 4167 - 4171
(2007/10/03)
-
- Isomerization reactions of the n-C4H9O and n-OOC4H8OH radicals in oxygen
-
Reactions of n-C4H9O radicals have been investigated in the temperature range 343-503 K in mixtures of O2/N2 at atmospheric pressure. Flow and static experiments have been performed in quartz and Pyrex vessels of different diameters, walls passivated or not towards reactions of radicals, and products were analyzed by GC/MS. The main products formed are butyraldehyde, hydroperoxide C4H8O3 of MW 104, 1-butanol, butyrolactone, and n-propyl hydroperoxide. It is shown that transformation of these RO radicals occurs through two reaction pathways, H shift isomerization (forming C4H8OH radicals) and decomposition. A difference of activation energies ΔE = (7.7 ± 0.1 (σ)) kcal/mol between these reactions and in favor of the H-shift is found, leading to an isomerization rate constant κisom (n-C4H9O) = 1.3 × 1012 exp(-9,700/RT). Oxidation, producing butyraldehyde, is proposed to occur after isomerization, in parallel with an association reaction of C4H8OH radicals with O2 producing OOC4H8OH radicals which, after further isomerization lead to an hydroperoxide of molecular weight 104 as a main product. Butyraldehyde is mainly formed from the isomerized radical HOCCCC. + O2 ? →O=CCCC + HO2, since (i) the ratio butyraldehyde/(butyraldehyde + isomerization products) = 0.290 ± 0.035 (σ) is independent of oxygen concentration from 448 to 496 K, and (ii) the addition of small quantities of NO has no influence on butyraldehyde formation, but decreases concentration of the hydroperoxides (that of MW 104 and rt-propyl hydroperoxide). By measuring the decay of [MW 104] in function of (NO] added (0-22.5 ppm) at 487 K, an estimation of the isomerization rate constant OOC4H8OH→ HOOC4H7OH, κ5 ≈ 1011exp(- 17,600/RT) is made. Implications of these results for atmospheric chemistry and combustion are discussed. ?1996 John Wiley and Sons, Inc.
- Heiss, Adolphe,Sahetchian, Krikor
-
p. 531 - 544
(2007/10/03)
-
- Reaction of Primary Alkyl Hydroperoxides with Sulphamoyl Chloride: Alkyl(sulphamoyl)peroxides. Peroxo Compounds, XVIII
-
The novel peroxides H2NSO2OOCH2R (1a: R=CH2CH3; 1b: R=CH2CH2CH3) are obtained by reaction of sulphamoyl chloride with the appropriate hydroperoxides in the presence of pyridine (temperature below -30 deg C, solvent diethyl ether).The solvent-free liquids 1 deflagrate at ca. 0 deg C.Hydrolysis or ammonolysis of 1 generates the hydroperoxide and sulphamic acid or sulphamide, respectively.Controlled thermolysis of 1 affords sulphamic acid and carbonyl compounds, i.e. propanal and n-propyl propanoate from 1a, butanal, 2-methylpropanal and n-butyl n-butyrate from 1b.These products suggest a nonradical cyclic decomposition path-way. - Keywords: Sulphamoyl chloride, reaction with n-alkyl hydroperoxides; n-Alkyl hydroperoxides, reaction with sulphamoyl chloride; Alkyl(sulphamoyl)peroxides, preparation and thermolysis
- Blaschette, Armand,Safari, Hassan
-
p. 875 - 880
(2007/10/02)
-
- UBER PEROXOVERBINDUNGEN 17 DARSTELLUNG UND EIGENSCHAFTEN VON ALKYL- UND TRIMETHYLSILYLDERIVATEN VON PEROXOSCHWEFELSAEUREN
-
The novel peroxides Me3SiOSO2OOR (3; R = n-C3H7, n-C4H9, n-C5H11), Na+-OSO2OOR (5; R = n-C3H7, n-C4H9), and HOSO2OOR (6; R = n-C3H7, n-C4H9) are obtained by insertion of SO3 in Me3SiOOR, NaOOR, and HOOR respectively (temperature below -20 deg C, solvent CH2Cl2).The solid compounds 5 are stable up to 40-50 deg C, the liquids 3 and 6 deflagrate at ca. -10 deg C.Hydrolysis of the sulfonyl peroxides generates HOOR in each case.Thermolysis of 3 affords the corresponding aldehydes by heterolysis of the (O-O)-bond.In CH2Cl2 at room temperature, Me3SiOSO2OOSiMe3 (1) undergoes a slow nucleophilic 1,2-rearrangement, forming the isomer Me3SiOSO2OSi(OMe)Me2 (7).The constitution of 7 is confirmed by chemical evidence, e. g. hydrolytic and thermal degradation.Thermolysis of Me3SiOSO2OOSO2OSiMe3 (2) at room temperature in CH2Cl2 occurs by a rather rapid free radical pathway, the solvent being attacked by H and/or Cl abstraction (main products: HCl, CO, ClSO2OSiMe3, Me3SiOSO2OSiMe3).The new trimethylsilyl(n-alkyl)-peroxides Me3SiOOR with R = n-C3H7, n-C4H9, and C5H11 were prepared and characterised.
- Blaschette, Armand,Safari, Hassan
-
-