Heteropolymolybdate as a New Reaction-controlled Phase-transfer Catalyst for Efficient Alcohol Oxidation with Hydrogen Peroxide

Aldehydes are very important raw materials or intermediates, which have widespread applications in the perfumery, pharmaceutical, dyestuff and agrochemical industries1. Oxidation of alcohol is one of the most frequently used synthetic reactions in the lab…     

A Simple Method for Synthesis of Methylene Dioximes Using Poly(ethylene glycol)‐400 as a Phase Transfer Catalyst

Abstract

A simple method for synthesis of methylene dioximes by reaction of ketoximes with dichloromethane in the presence of aqueous sodium hydroxide solution using poly (ethylene glycol)‐400 (PEG‐400) as a phase transfer catalyst is described.     

Microwave‐Assisted Epoxidation of Simple Alkenes in the Presence of Hydrogen Peroxide

A novel application of microwave irradiation for the epoxidation of some simple alkenes, in which hydrogen peroxide was used as an oxidant together with sodium tungsten and phosphorous acid under phase‐transfer catalytic (PTC) conditions, is described as a new environmentally benign method. In comparison with conventional heating, the microwave process is a very useful alternative for introducing of the oxirane ring into some unsaturated hydrocarbons because of reduction of the reaction time and increase in yield.     

Efficient and Rapid Method for the Oxidation of Electron‐Rich Aromatic Aldehydes to Carboxylic Acids Using Improved Basic Hydrogen Peroxide

An efficient and rapid method for oxidation of electron‐rich aromatic aldehydes to their corresponding carboxylic acids in excellent yields was developed. It is based on the oxidation of methoxy‐substituted benzaldehydes in methanol with an improved aqueous basic hydrogen peroxide system. Benzaldehydes with electron‐withdrawing substituents are oxidized to the corresponding carboxylic acid in excellent yields under mild reaction conditions.     

Mild Oxidation of Alcohols with o‐Iodoxybenzoic Acid (IBX) in a Water/CH2Cl2 Mixture in the Presence of Phase‐Transfer Catalyst

A mild oxidation of alcohols to the respective carbonyl compounds with o‐iodoxybenzoic acid (IBX) catalyzed by n‐Bu₄NBr in a water/dichloromethane (1:1) mixture is described. The method offers the advantage of a simple, inexpensive catalyst and the diminution of organic solvent employed in the reaction.     

Kinetics and Mechanism of 2,3,6-Trimethylphenol Oxidation by Hydrogen Peroxide in the Presence of TiO2–SiO2 Aerogel

The product and kinetics studies of 2,3,6-trimethylphenol (TMP) oxidation by 30% aqueous ₂₂ in the presence of a heterogeneous catalyst, TiO₂–SiO₂ aerogel, are performed in an MeCN medium. The main reaction products are 2,3,5-trimethyl-1,4-benzoquinone and 2,2",3,3",6,6"-hexamethyl-4,4"-biphenol. The reaction is first-order in ₂₂ and fractional order (1–0) in TMP. The reaction rate is proportional to the catalyst amount and depends on the water concentration in the reaction mixture in a complex manner. The results suggest the formation of an active intermediate on the titanium center. In this intermediate containing both a TMP molecule and the hydroperoxide group, inner-sphere one-electron oxidation of TMP occurs to give the phenoxyl radical.     

Preferential Oxidation of CO in Excess Hydrogen over CuO-CeO2 Catalyst Prepared by Chelating Method

The CuO-CeO2 catalyst prepared by chelating method has a superior catalytic performance for the preferential oxidation of CO in rich hydrogen, compared with the CuO-CeO2 catalyst prepared by coprecipitation method. The CO conversions over these catalysts, at 120℃and 120000 ml/(g-h) in the absence of CO2 and H2O, are 99.6% and 88.6%, respectively, and the selectivity of O2 over these catalysts is very close (i.e. 51.3% and 55.8%, respectively). The influence of certain factors such as hydrogen concentration, carbon monoxide concentration, H2O, O2/CO ratios, and space velocity on the catalytic performance of CuO-CeO2 catalyst prepared by chelating method is also studied. The results show that the addition of hydrogen and H2O has a negative effect on the catalytic performance of CuO-CeO2 catalyst, however, the variation of space velocity and the O2/CO ratio causes a comparatively slight influence.     

Useful Application of Acidic Ionic Liquids as Solvents in Baeyer–Villiger Oxidation with Hydrogen Peroxide for the Synthesis of Lactones

Cyclic ketones have been efficiently oxidized with hydrogen peroxide using acidic ionic liquids (ILs) as solvents. This is a new method for the synthesis of lactones with high yields that does not utilize any additional catalysts and enables ILs to be recycled.     

A Facile Method for the Epoxidation of Cyclic Enone Catalyzed by tert-BuNH2 with 30% Hydrogen Peroxide as Oxidant

It was found that tert-BuNH_2 is an efficient catalyst for epoxidation of α,β-unsaturated ketones with 30% H_2O_2under mild conditions.For most of the cyclic unsaturated ketones used,moderate to excellent yields (45%—93%)were obtained within 24 h period.     

In situ Polypropylene Nanocomposites: Gas‐Phase Polymerization of Propylene in the Presence of Nanofillers using Nanosilica‐Supported‐Zirconocene Catalyst

This work concentrates on using the gas‐phase polymerization technique for the production of highly loaded nanocomposites. Filler loading levels near the vicinity of 40 wt% have been obtained using different nanofillers. Three different in situ Polypropylene (PP) nanocomposites, i.e., Cloisite‐20A filled polypropylene (CFPP), Kaolin filled polypropylene (KFPP) and nanosilica filled polypropylene (SFPP) have been prepared by gas‐phase polymerization. The catalyst used is Nanosilica‐Supported‐Zirconocene. The fillers used are Closite‐20A, Kaolin and nanosilica, respectively. These were pre‐treated with MAO (Methylaluminoxane) to inhibit their deactivating action on the catalyst because of the presence of either acidic or basic groups on their surfaces; in this way MAO acts as a co‐catalyst for the three polymerization reactions being discussed. Significantly higher molecular weight polypropylene was formed with nanosilica as the filler. The melting temperature and enthalpy is also observed to be comparatively higher in this case. However, in the case of other fillers, the molecular weights, as well as melting points, are comparatively lower. With the catalyst used, a mixture of crystalline and amorphous polypropylene was observed to form. Comparatively lesser amounts of crystalline polypropylene are also observed.     

[α‐PW12O40]3− Immobilized on Ionic Liquid–Modified Polymer as a Heterogeneous Catalyst for Alcohol Oxidation with Hydrogen Peroxide

Ionic liquid–modified polystyrene resin beads were demonstrated to be an appropriate support for polyoxometalate. In this heterogeneous catalytic system, alcohols can be efficiently oxidized to corresponding carbonyl groups with H₂O₂ in CH₃CN. The catalyst can be easily recovered by filtration and recycled without apparent loss of catalytic performance.     

Amberlite IRA-400 (OH−) as a Catalyst in the Preparation of 4H-Benzo[b]pyrans in Aqueous Media

A quaternary ammonium hydroxide–type of anion exchange resin (Amberlite IRA-400) was found to be an effective and reusable catalyst for the synthesis of various 4H-benzo[b]pyran derivatives via a one-pot, three-component condensation in aqueous media. Short reaction time, easy and quick isolation of the products, environmentally friendly procedure, excellent chemoselectivity, and excellent yields are the main advantages of this procedure.     

Facile One‐Step Conversion of Ketones into α‐Azidoketones using [Hydroxy(tosyloxy)iodo]benzene and Sodium Azide in the Presence of a Phase‐Transfer Catalyst under Solvent‐Free Conditions

We have described a one‐step, solvent‐free synthesis of α‐azidoketones from the corresponding ketones that requires relatively benign [hydroxy(tosyloxy) iodo]‐benzene reagent, sodium azide, and phase‐transfer catalyst at room temperature. Generality of the protocol has been demonstrated by synthesizing various α‐azidoketones high in yield and purity within a short time.     

Diammonium Hydrogen Phosphate as a Neutral and Efficient Catalyst for Synthesis of 1,8‐Dioxo‐octahydroxanthene Derivatives in Aqueous Media

A new and efficient method to synthesize a 3,3,6,6,9‐aryl‐1,8‐dioxo‐octahydroxanthene derivative using diammonium hydrogen phosphate as catalyst was performed in water at room temperature in a short periods.     

C–C Bond Rupture in the Oxidation of Lower (C2–C6) Alcohols with Hydrogen Peroxide Mediated by Iron-Containing Compounds

C–C bond rupture upon the oxidation of alcohols in the Fe(ClO₄)₃+ H₂O₂system in aqueous acetonitrile at room temperature is found. The relative yield of the products of C–C bond rupture is 20–30% under standard conditions for C₂and C₃alcohols and decreases in the series C₂> C₃> C₄> C₆. The alkyl radical and carboxylic acid are the products of C–C bond rupture in alcohol oxidation. Cyclohexane is a competitive inhibiting agent for C–H bond oxidation in 1-propanol, and it does not affect the yield of the products of C–C bond rupture. When H₂O₂is replaced by tert-BuOOH, the fraction of the products of C–C bond rupture decreases by an order of magnitude. Our data suggest that a non-radical intermediate, likely Fe(III) hydroperoxo complex, is responsible for C–C bond rupture in alcohol under the reaction conditions.     

Studies on the Phase Separation of Poly(Ether Imide)‐Modified Cyanate Ester Resin

Abstract

A high temperature thermosetting bisphenol‐A dicyanate (BADCy) was blended with a novel thermoplastic poly(ether imide) (PEI) at various composition. The phase separation behavior during isothermal curing was studied by differential scanning calorimeter (DSC), time‐resolved light scattering (TRLS), scanning electron microscopy (SEM), and rheological measurements. The results suggested that the phase structure changed from separated phase, via co‐continuous phase, to phase inversion with the increase of the PEI content. The curing conversion of BADCy was slightly affected by the composition in the blend and the curing rate was decreased with the increase of PEI content. The co‐continuous phase morphology was attributed to a spinodal decomposition. The initial concentration of PEI had an effect on the rheological behavior during phase separation. It was found by tensile test that the blend with 15 wt.% PEI had higher tensile strength and elongation at break than that without PEI.     

An Iron(III)-Monoamidate Complex Catalyst for Selective Hydroxylation of Alkane CH Bonds with Hydrogen Peroxide

Selective oxidation: The success of the title reaction is caused by the strong electron donation from the amidate moiety of the dpaq ligand to the iron center (dpaq=2-[bis(pyridin-2-ylmethyl)]amino-N-quinolin-8-yl-acetamidate). This process facilitates the O?O bond heterolysis of the intermediate Fe(III) OOH species to generate a selective oxidant without forming highly reactive hydroxyl radicals.     

Note a Kinetic Study of the Photopolymerization of N,N Methylenebisacrylamide Initiated by N‐Bromo‐Succinimide in the Presence and Absence of Isopropyl Alcohol

The photopolymerization of N,N′‐methylenebisacrylamide has been studied with N‐bromosuccinimide as photoinitiator in the presence and absence of isopropyl alcohol (ISP). The rate of polymerization in the presence of ISP was found to be very high, and this is explained on the basis of the relative reactivities of the initiating radicals. A probable mechanism consistent with the observed results is proposed and discussed.     

Kinetics of the Oxidation of Phenylhydrazine by [Fe(CN)6]3− in Water‐in‐Oil Microemulsions

The oxidation reaction of phenyl hydrazine (Phh) by hexacyanoferrate ([Fe(CN)₆]^3?) has been studied in water‐in‐oil (w/o) microemulsion media. The kinetic profile of the reaction was investigated as a function of [Phh], droplet size, and droplet concentration. Comparison of the kinetic profiles of the reaction in microemulsion, water‐urea, and water‐AOT‐urea media indicates that the kinetic profile of the reaction in microemulsion shows a behavior similar to that of the reaction in water‐AOT‐urea medium at 4 M urea. An initial increase and then a decrease in k_obs is observed with increasing molar ratio, W_o(=[H₂O]/[AOT]) at constant [AOT] (=0.4 M), whereas k_obs decreases upon increasing the AOT concentration at constant molar ratio.     

Enhancement in Activity of a Vanadium Catalyst for the Oxidation of Sulfur Dioxide by Radio Frequency Plasma During the Preparation Process

Radio frequency plasma was used to prepare a vanadium catalyst. The results showed that activating time of the catalyst could be shortened quickly and the catalytic activity was improved to some extent with the use of plasma. Catalyst Ls-9 was prepared under an optimal condition of 40 W discharge power, 10 min discharge time and 8 Pa gas pressure. The catalytic activity was up to 54.7% at 410℃,which was 2.2% higher than that of the Ls-8 catalyst. Only 10 min was needed to activate the catalyst with plasma, which was 1/9 of the traditional calcination time. For Ls-9, both the endothermic as well as the exothermic peaks detected by differential thermal analysis shifted to higher temperatures obviously, indicating that its crystal phase could melt easily. There existed an apparent endothermic peak at 283℃. SEM photographs showed a uniform size distribution. It is inferred that the quadrivalent vanadium compound may exist mainly in the form of VOSO4.