Showing papers on "Cyclohexanone published in 2002"

Sonochemical Synthesis of Mesoporous Iron Oxide and Accounts of Its Magnetic and Catalytic Properties

Abstract: Synthesis of mesoporous iron oxides has been reported using a sonochemical technique. Iron(III) ethoxide was used as an inorganic precursor and CTAB as an organic structure directing agent. After sonication the surfactant was removed by calcination and solvent extraction methods. FTIR spectra demonstrated the removal of the surfactant from the pores of the mesoporous iron oxide. The calcinated material was characterized by XRD, TEM, TGA, and BET surface area measurements. The surface area after solvent extraction is found to be 274 m2/g. The magnetic and catalytic properties of the materials have been studied. The as-prepared amorphous Fe2O3 has shown a paramagnetic behavior, while after calcination at 350 °C it changes to γ-Fe2O3 with good magnetic properties. The catalytic activity of mesoporous iron oxide was studied in the reaction of cyclohexane oxidation under mild conditions. The mesoporous Fe2O3 catalyst has shown high conversion of cyclohexane into cyclohexanone and cyclohexanol, with a high sele...

Studies on the selective transport of organic compounds by using ionic liquids as novel supported liquid membranes.

Abstract: The possibility of using room-temperature ionic liquids (RTILs) in bulk (nonsupported) and supported liquid membranes for the selective transport of organic molecules is demonstrated. A systematic selective transport study, in which 1,4-dioxane, propan-1-ol, butan-1-ol, cyclohexanol, cyclohexanone, morpholine, and methylmorpholine serve as a model seven-component mixture of representative organic compounds, and in which four RTILs based on the 1-n-alkyl-3-methylimidazolium cation (n-butyl, n-octyl, and n-decyl) are used together with the anions PF(6)(-) or BF(4)(-), immobilized in five different supporting membranes, confirms that the combination of the selected RTILs with the supporting membranes is crucial to achieve good selectivity for a specific solute. The use of the RTIL 1-n-butyl-3-methylimidazolium hexafluorophosphate, immobilized in a polyvinylidene fluoride membrane, allows an extremely highly selective transport of secondary amines over tertiary amines (up to a 55:1 ratio). The selective transport of a given solute through the RTIL/membrane system results from the high partitioning of the solute to the liquid membrane phase which, in the case of amines, is rationalized mainly by the formation of a preferential substrate/H[bond]C(2) hydrogen bonding to the imidazolium cation.

Selective hydrogenation of phenol to cyclohexanone over supported Pd and Pd-Ca catalysts: an investigation on the influence of different supports and Pd precursors

Abstract: The gas-phase selective hydrogenation of phenol to cyclohexanone has been investigated over supported Pd catalysts in order to clarify the role of the support, the Pd precursor and the addition of Ca in controlling activity, selectivity and stability of the catalytic system. The catalytic results showed that over monometallic Pd catalysts prepared by PdCl2 as precursor the order of activity and selectivity to cyclohexanone was the following: Pd/La2O3>Pd/CeO2>Pd/Al2O3. The same order of activity was observed over ex-Pd(CH3COO)2 catalysts. However, over these latter samples the selectivity to cyclohexanone was very high regardless of the support used. Addition of calcium strongly improved the catalytic performance of both ex-chloride and ex-acetate Pd catalysts supported on alumina, whereas no significant improvement was observed on Pd catalysts supported on CeO2 and La2O3. On the basis of characterization data (CO chemisorption, TPD and FT-IR) reported in this paper it has been suggested that the acid–base properties of supported Pd catalysts strongly influence the adsorption–desorption equilibrium of the reactant and products, being responsible for directing the selectivity to the reaction products. The catalytic activity of the system appears to be, instead, mainly controlled by the palladium sites on which hydrogen is activated.

Iron perchlorophthalocyanine and tetrasulfophthalocyanine catalyzed oxidation of cyclohexane using hydrogen peroxide, chloroperoxybenzoic acid and tert-butylhydroperoxide as oxidants

Abstract: Polychlorophthalocyanine (Cl 16 PcFe II ) and tetrasulfophthalocyanine ([Fe II TSPc] 4− ) complexes of iron are employed as catalysts for the oxidation of cyclohexane using tert -butyl hydroperoxide (TBHP), m -chloroperoxybenzoic acid ( m -CPBA) and hydrogen peroxide as oxidants. Catalysis using the Cl 16 PcFe II was performed in a dimethylformamide:dichloromethane (3:7) solvent mixture. For the [Fe II TSPc] 4− catalyst, a water:methanol (1:9) mixture was employed. The products of the catalysis are cyclohexanone, cyclohexanol and cyclohexanediol. The relative yields of the products depended on oxidant and the catalyst. TBHP was found to be the best oxidant since minimal destruction of the catalyst and higher selectivity in the products were observed when this oxidant was employed. The mechanism of the oxidation of cyclohexane in the presence of the Cl 16 PcFe II and [Fe II TSPc] 4− involves the oxidation of these catalysts, forming an Fe(III) phthalocyanine species as an intermediate. Higher yields were observed when [FeTSPc] 4− was employed as a catalyst, which is more soluble than the perchlorinated iron phthalocyanine catalyst.

Manifestation of Stereoelectronic Effects on the Calculated Carbon−Hydrogen Bond Lengths and One Bond 1JC-H NMR Coupling Constants in Cyclohexane, Six-Membered Heterocycles, and Cyclohexanone Derivatives

Abstract: Cyclohexane (1), oxygen-, sulfur-, and/or nitrogen-containing six-membered heterocycles 2−5, cyclohexanone (6), and cyclohexanone derivatives 7−16 were studied theoretically [B3LYP/6-31G(d,p) and P...

An efficient enzymatic Baeyer-Villiger oxidation by engineered Escherichia coli cells under non-growing conditions.

Abstract: Economical methods of supplying NADPH must be developed before biotransformations involving this cofactor can be considered for large-scale applications. We have studied the enzymatic Baeyer-Villiger oxidation of cyclohexanone as a model for this class of reactions and developed a simple approach that uses whole, non-growing Escherichia coli cells to provide high productivity (0.79 g epsilon-caprolactone/L/h = 18 micromol epsilon-caprolactone/min/g dcw) and an 88% yield. Glucose supplied the reducing equivalents for this process, and no exogenous cofactor was required. The volumetric productivity of non-growing cells was an order of magnitude greater than that achieved with growing cells of the same strain. Cells of an engineered E. coli strain that overexpresses Acinetobacter sp. cyclohexanone monooxygenase were grown under inducing conditions in rich medium until the entry to stationary phase; the subsequent cyclohexanone oxidation was carried out in minimal salts medium lacking a nitrogen source. After the biotransformation was complete, the lactone product was adsorbed to a solid support and recovered by washing with an organic solvent.

Study of the Catalytic Behavior of Montmorillonite/Iron(III) and Mn(III) Cationic Porphyrins

Abstract: Two samples of montmorillonite (one of Brazilian origin, BNC1 clay, and the other STX-1, supplied by the Clay Mineral Society Repository (University of Missouri, USA) were allowed to react with biomimetic metalloporphyrins of Fe(III) and Mn(III) in cationic form. The compounds were characterized by several techniques, showing that the metalloporphyrins molecules were adsorbed at the surface of the clay platelet crystals. The catalytic activities of the intercalated complexes for the oxidation of alkane were dependent upon the concentration of the porphyrin immobilized in the clay and factors such as the metal ion species in the porphyrins, choice of solvent, and concentration of the iodosylbenzene oxidant. Good selectivity to cyclohexanol instead of cyclohexanone was observed for the catalytic oxidation of cyclohexane by iodosylbenzene.

Non-catalytic liquid phase oxidation of alkenes with nitrous oxide. 1. Oxidation of cyclohexene to cyclohexanone

Abstract: A very efficient way of cyclopentanone production via selective liquid phase oxidation of cyclopentene with nitrous oxide is reported. When contacting liquid cyclopentene at high temperature, nitrous oxide is able to interact directly with the C=C double bond of the hydrocarbon and transfer its oxygen to unsaturated carbon atom. The reaction occurs without catalyst with nearly 100% selectivity.

Increasing the ketone selectivity of the cobalt-catalyzed radical chain oxidation of cyclohexane.

Abstract: A variety of heterogeneous catalysts for the radical chain oxidation of cyclohexane has been prepared by immobilization of the well-defined cobalt acetate oligomers [py(3)Co(3)(mu(3)-O)(OH)(O(2)CCH(3))(5)](PF(6)) (1) and [py(4)Co(2)(OH)(2)(O(2)CCH(3))(3)](PF(6)) (2) on carboxy-modified mesoporous silica supports A-D by carboxylate exchange. The catalytic oxidation of cyclohexane with tert-butyl hydroperoxide (TBHP) in the presence of these homogeneous and immobilized cobalt acetate complexes afforded the corresponding alcohol and ketone in high yield. The immobilization of 1 and 2 results in a significant increase of catalytic activity. TBHP acts as a radical initiator and as source of molecular oxygen, which is also involved in the overall oxidation process. The rate of cyclohexane conversion is limited by the diffusion of molecular oxygen, and steady-state concentrations of cyclohexanone (K, ketone) and cyclohexanol (A, alcohol) are established; these determine the maximum K:A ratio.

Activity enhancement by acetic acid in cyclohexane oxidation using Ti-containing zeolite catalyst

Abstract: Titanium silicalite (TS-1) was hydrothermally crystallised from a titanosilicate gel. The solid material was characterised by XRD, IR, and SEM, and then used as a catalyst in the liquid phase oxidation of cyclohexane with hydrogen peroxide. The reaction was carried out for 6 h, at the temperature between 40 and 80 °C. It was found that a marked increase in the catalytic activity was observed in the reaction using acetic acid as the solvent, as compared to those using no solvent and methyl ethyl ketone. Further investigation was made on the cause of activity enhancement, and it was shown that acetic acid was readily oxidised to peracetic acid. This compound was believed to facilitate the complexation of the framework titanium active sites, and subsequently serve as a better oxidising agent, as compared to the original hydrogen peroxide. However, leaching of the titanium species was also observed in small amounts, from the reaction using acetic acid as the solvent. In the mechanistic point of view, there was an evidence suggesting that cyclohexanol might be a primary product from the cyclohexane oxidation, and can be consecutively re-oxidised to form cyclohexanone. It is noted that the direct oxidation from cyclohexane to cyclohexanone cannot be excluded.

Study of cyclohexanol decomposition reaction over the ferrospinels, A1−xCuxFe2O4 (A=Ni or Co and x=0, 0.3, 0.5, 0.7 and 1), prepared by ‘soft’ chemical methods

Abstract: Preparation of simple and mixed ferrospinels of nickel, cobalt and copper and their sulphated analogues by the room temperature coprecipitation method yielded fine particles with high surface areas. Study of the vapour phase decomposition of cyclohexanol at 300 ◦ C over all the ferrospinel systems showed very good conversions yielding cyclohexene by dehydration and/or cyclohexanone by dehydrogenation, as the major products. Sulphation very much enhanced the dehydration activity over all the samples. A good correlation was obtained between the dehydration activities of the simple ferrites and their weak plus medium strength acidities (usually of the Brnsted type) determined independently by the n-butylamine adsorption and ammonia-TPD methods. Mixed ferrites containing copper showed a general decrease in acidities and a drastic decrease in dehydration activities. There was no general correlation between the basicity parameters obtained by electron donor studies and the ratio of dehydrogenation to dehydration activities. There was a leap in the dehydrogenation activities in the case of all the ferrospinel samples containing copper. Along with the basic properties, the redox properties of copper ion have been invoked to account for this added activity. © 2002 Elsevier Science B.V. All rights reserved.

Bulk polymerization of styrene catalyzed by bi- and trifunctional cyclic initiators

Abstract: A study of the bulk free-radical polymerization of styrene in the presence of the cyclic bi- and trifunctional initiators cyclohexanone triperoxide, diethylketone triperoxide, acetone triperoxide, cyclohexanone diperoxide, and pinacolone diperoxide is reported. When these multifunctional initiators are used for styrene polymerization at high temperatures, it is possible to produce polymers with high molecular weights and narrow polydispersities at a high reaction rate. Additionally, the former initiators are used in a mixture that shows that the molecular parameters are influenced by the initiator concentration in the initiation system, in addition to the system employed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1–11, 2002

Hydrogenation of Phenol by the Pd/Mg and Pd/Fe Bimetallic Systems under Mild Reaction Conditions

Abstract: Three palladium-catalyzed zerovalent metal systems were found to be able to hydrogenate phenol to cyclohexanol and cyclohexanone under room temperature and pressure conditions. Exposure of 5.0 mM aqueous phenol solutions to Pd (2.6 ppt m/m)/Mg (1.00 g 20 mesh) and to 0.53 g of 1/8 in. Pd (0.5%)/alumina in contact with 1.00 g 20 mesh Mg results in 74% and 24% destruction of the reactant after 6 h of reaction time. The latter system was found to be greatly enhanced in the presence of 2% (v/v) glacial acetic acid, resulting in an 84% reduction of phenol with a carbon balance of 93%. Palladized iron and unmodified metals systems were much less effective at hydrogenating phenol. The advantage of the 1/8 in. Pd/alumina/20 mesh Mg system is that it gives a readily recoverable form of the catalysts when compared to the bimetallic systems.

Preparation of Heterogeneous Vanadium (VO2+) Catalyst for Selective Hydroxylation of Cyclohexane by Molecular Oxygen

Abstract: A vanadium(II) Schiff base ligand, [1,4-bis (salicylidene amino)-phenylene] vanadium oxo complex bonded on carbamate-modified silica gel, has been synthesized. The liquid-phase oxidation reaction of cyclohexane with this catalyst was found to give cyclohexanol at moderate condition (reaction temperature 200 °C, pressure 23.8 atm, catalyst concentration 1.0% and 16 h of reaction time) with considerably higher specificity (18:1 ratio with cyclohexanone and negligible acid formation). The catalyst has been tested for 200 h of reaction and the leaching of the metal occurs negligibly.

Oxidation of a cyclohexanone derivative using a brevibacterium cyclohexanone monooxygenase

Abstract: Two gene clusters have been isolated from an Brevibacterium sp HCU that encode the enzymes expected to convert cyclohexanol to adipic acid. Individual open reading frames (ORF's) on each gene cluster are useful for the production of intermediates in the adipic acid biosynthetic pathway or of related molecules. All the ORF's have been sequenced. Identification of gene function has been made on the basis of sequence comparison and biochemical analysis.

Synthesis of Polysubstituted Benzothiophenes and Sulfur-Containing Polycyclic Aromatic Compounds via Samarium Diiodide Promoted Three-Component Coupling Reactions of Thiophene-2-carboxylate

Abstract: By the promotion of samarium diiodide, thiophene-2-carboxylate reacted with 2 equiv of ketones at the C-4 and C-5 positions to give diols such as 2 and 9. Because the intermediary organosamarium species were oxophilic but not too basic, the double hydroxyalkylations with various ketone substrates, including alkyl aryl ketones, acetylthiophenes, cyclohexanone, α-tetralone, and α-phenylacetophenones, were realized without complication of side reactions. The diol products underwent an acid-catalyzed dehydration to give dienes such as 3 and 10, which were treated with DDQ to give either polysubstituted thiophenes (e.g., 4 and 11) or benzothiophenes (e.g., 5, 13, and 14) depending on the reaction conditions. Oxidative annulations of 4,5-diarylthiophenes 11 and 4,5,6,7-tetraphenylbenzothiophenes 14 were carried out by photochemical or chemical methods to give the sulfur-containing polycyclic aromatic compounds, such as phenanthro[9,10-b]thiophene-2-carboxylate, piceno[13,14-b]thiophene-2-carboxylate, and triben...

Thio bis (β-diketonato)-bridged binuclear ruthenium(III) complexes containing triphenylphosphine or triphenylarsine. Synthetic, spectral, catalytic and antimicrobial studies

Abstract: Hexacoordinated binuclear ruthenium(III) complexes of the type {[RuX2(EPh3)2]2(bis-β-dk)} [X = Cl or Br; bis-β-dk = thiobis(β-diketone)] have been prepared by reacting [RuCl3(PPh3)3], [RuCl3(AsPh3)3], [RuBr3(AsPh3)3] or [RuBr3(PPh3)2(MeOH)] with thiobis(β-diketones) in a 2:1 molar ratio in benzene, and characterized by analytical, spectroscopic (i.r., electronic e.p.r.) and cyclic voltammetric data. An octahedral structure has been proposed. The complexes are effective catalysts for the oxidation of PhCH2OH and cyclohexanol to PhCHO and cyclohexanone respectively using N-methylmorpholine-N-oxide as co-oxidant. Some of the complexes have been subjected to antifungal activity studies.

Purification and characterization of a cyclohexanol dehydrogenase from Rhodococcus sp. TK6

Abstract: Activity staining on the native polyacrylamide gel electrophoresis (PAGE) of a cell-free extract of Rhodococcus sp. TK6, grown in media containing alcohols as the carbon source, revealed at least seven isozyme bands, which were identified as alcohol dehydrogenases that oxidize cyclohexanol to cyclohexanone. Among the alcohol dehydrogenases, cyclohexanol dehydrogenase II (CDH II), which is the major enzyme involved in the oxidation of cyclohexanol, was purified to homogeneity. The molecular mass of the CDH II was determined to be 60 kDa by gel filtration, while the molecular mass of each subunit was estimated to be 28 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The CDH II was unstable in acidic and basic pHs, and rapidly inactivated at temperatures above 40°C. The CDH II activity was enhanced by the addition of divalent metal ions, like Ba 2+ and Mg 2+ . The purified enzyme catalyzed the oxidation of a broad range of alcohols, including cyclohexanol, trans-cyclohexane-1,2-diol, trans-cyclopentane-1,2-diol, cyclopentanol, and hexane-1,2-diol. The K m values of the CDH II for cyclohexanol, trans-cyclohexane-1,2-diol, cyclopentanol, trans-cyclopentane-1,2-diol, and hexane-1,2-diol were 1.7, 2.8, 14.2, 13.7, and 13.5 mM, respectively. The CDH II would appear to be a major alcohol dehydrogenase for the oxidation of cyclohexanol. The N-terminal sequence of the CDH II was determined to be TVAHVTGAARGIGRA. Furthermore, based on a comparison of the determined sequence with other short chain alcohol dehydrogenases, the purified CDH II was suggested to be a new enzyme.