Conventional Heating Conditions Research Articles

Study of microwave effects on the lipase-catalyzed hydrolysis

The effect of microwave heating on lipase-catalyzed reaction remains controversial. It is not clear whether the reaction rate enhancements are purely due to thermal/heating effects or to non-thermal effects. Therefore, quantitative mass spectrometry was used to conduct accurate kinetic analysis of lipase-catalyzed hydrolysis of triolein by microwave and conventional heating. Commercial lipases from Candida rugosa (CRL), Porcine Pancreas (PPL), and Burkholderia cepacia (BCL) were used. Hydrolysis reactions were performed at various temperatures and pH levels, along with various amounts of buffer and enzymes. Hydrolysis product yields at each time point using an internal-standard method showed no significant difference between microwave and conventional heating conditions when the reaction was carried out at the same temperature. CRL showed optimum catalytic activity at 37°C, while PPL and BCL had better activities at 50°C. The phosphate buffer was found to give a better hydrolysis yield than the Tris–HCl buffer. Overall results prove that a non-thermal effect does not exist in microwave-assisted lipase hydrolysis of triolein. Therefore, conventional heating at high temperatures (e.g., 50°C) can be also used to accelerate hydrolysis reactions.

Synthesis of 1,3,4-oxadiazole derivatives from α-amino acid and acyl hydrazides under thermal heating or microwave irradiation conditions

A series of new 2,5-disubstituted 1,3,4-oxadiazoles was synthesized under conventional thermal heating and microwave irradiation conditions through the reaction of acyl hydrazides with N- protected α-amino acid in presence of a small amount of POCl3. Heterocycles were obtained in moderate to good yields and in relatively short reaction times.

Microwave-Assisted, Multicomponent, Ecofriendly Synthesis of 3-Bihetaryl-2-oxindole Derivatives Grafted with Phenothiazine Moiety

A series of 3-(3′-pyrrolyl)-2-oxindoles incorporating the phenothiazine moiety has been synthesized under both conventional and microwave heating conditions via multicomponent reaction of 3-(2-(phenothiazin-2-yl)-2-oxoethylidene)-2-oxindole derivatives, acyclic and cyclic 1,3-dicarbonyl compounds, and ammonium acetate. The resulting 2-oxindole derivatives underwent selective chloroacetylation at both the oxindole and the phenothiazine NH groups. Treatment of the dichloroacetylated compound with 2 mol of sodium azide in acetone under reflux gave the corresponding monoazide with concomitant dechloroacetylation of the N-chloroacetyl group of the oxindole ring. Huisgen 1,3-dipolar cycloaddition of the resulted alkyl azide with diethyl acetylene–dicarboxylate afforded the corresponding triazole derivative in good yield. Furthermore, the dichloroacetylated compound could be easily cyclized into 4-(3-oxo-2,3-dihydroxazolo[3,2-a]indol-9-yl)-1H-pyrrole-3-carboxylate derivative by treatment with sodium hydride in dry toluene. The yields and rate of reactions significantly improved under microwave heating conditions.

Evaluation of Mechanical Properties of the Rocket Thrust Chamber Material under Flight Conditions

Thrust chamber of rocket engines often operate under conditions of rapid heating environments with temperatures approaching the melting points of the materials involved. Therefore, for the optimum design of rocket engines, it is necessary to obtain the properties of thrust chamber materials under actual operating conditions. The heating rates and loading rates in conventional (laboratory) tensile stress-strain tests, which are intended to evaluate the high temperature tensile properties of the materials, are usually very low compared to that actually encountered in rocket engines. The heating rates in conventional stress-strain tests are of the order of 0.4K per second to 0.5K per second only, whereas the combustion and aerodynamic heating rates in rockets and re-entry vehicles will usually exceed 100K per second. In this context, a very important beginning has been made to experimentally determine the high temperature tensile properties of KC20WN (a cobalt based superalloy) used in earth storable liquid rocket engine thrust chamber under conditions of rapid rates of heating which actually exists during flight. These investigations have shown that the elevated temperature strength of KC20WN depends upon the heating rate (or heating time) and can be considerably higher for rapid-heating conditions than for conventional heating conditions.

Microwave-Assisted Oxidative Degradation of Lignin Model Compounds with Metal Salts

A systematic study on microwave-assisted oxidative degradation of lignin model compounds, such as 2-phenoxy-1-phenylethanol, vanillyl alcohol, and 4-hydroxybenzyl alcohol, was performed by evaluating the catalytic activity of 14 types of metal salts. The acidity of each metal salt solution for the oxidative degradation of 2-phenoxy-1-phenylethanol, vanillyl alcohol, and 4-hydroxybenzyl alcohol under the microwave irradiation and conventional heating conditions was measured and compared. The results showed that CrCl3 and MnCl2 were the most effective for the degradation of the lignin model compounds. The acidity of metal salt is in favor of the catalytic activity for the degradation of 2-phenoxy-1-phenylethanol, vanillyl alcohol, and 4-hydroxybenzyl alcohol, and microwave irradiation is able to accelerate the degradation rate in a large scale. The possible mechanisms for the degradation of 2-phenoxy-1-phenylethanol, vanillyl alcohol, and 4-hydroxybenzyl alcohol are proposed on the basis of the product dist...

ChemInform Abstract: Nickel Catalyzed [3 + 2] Cycloaddition Reaction of Bis(methylenecyclopropane) with Cyclic and Acyclic Dienophiles.

AbstractThe cycloaddition reactions are performed under conventional heating conditions or microwave irradiation to form cyclopentane derivatives.

Nanomagnetic‐supported Sulfonic Acid: Simple and Rapid Method for the Synthesis of α,α′‐Bis‐(substituted‐benzylidene) Cycloalkanones

AbstractNanomagnetic‐supported sulfonic acid is found to be a powerful and reusable heterogeneous catalyst for the rapid synthesis of α,α′‐bis‐(substituted‐benzylidene)cycloalkanones under conventional heating and solvent free conditions. High yield, simple work up and easy recovery of the catalyst are the most obvious advantages of this procedure.

ChemInform Abstract: Synthesis of Phenanthridine Derivatives Functionalized in the C‐Ring by Means of IMDAF Reactions under Microwave or Conventional Heating Conditions.

AbstractThe results of the intramolecular reactions of substrates (I) and (VII) are highly dependent on the substituents and on the reaction conditions.

ChemInform Abstract: Highly Active Recyclable Heterogeneous Nanonickel Ferrite Catalyst for Cyanation of Aryl and Heteroaryl Halides.

Magnetic nickel ferrite nanoparticles are found to be an efficient catalytic system for cyanation reactions of various types of aryl halides under conventional heating conditions. All the reactions result in very good to excellent yields under optimized reaction conditions. Furthermore, the catalyst is easily removed from the reaction medium and can be reused further in several subsequent runs. Copyright © 2014 John Wiley & Sons, Ltd.

Microwave Assisted Reactions of Natural Oils: Transesterification and Hydroformylation/Isomerization as Tools for High Value Compounds

A comparative study on the transesterification of natural oils obtained from Calophyllum inophyllum seeds was carried out using homogeneous (NaOH/MeOH) or heterogeneous catalysts, with conventional heating and under microwave irradiation. The results show that the microwave-assisted reaction using heterogeneous catalysts, obtained from renewable sources (rice husk and egg shell ashes), constitutes an energetically sustainable approach for transesterification. In order to obtain value-added products from natural oils, rhodium/monophosphite catalysts were applied to the hydroformylation of methyl oleate, also under conventional heating or microwave irradiation. Using conventional heating conditions (T = 80°C; Psyngas = 30 bar), high catalytic activity was observed with 98% chemoselectivity for aldehydes, while under microwave irradiation, using a CEM® Discover system equipped with syngas addition kit, high conversions were observed under mild reaction conditions (T = 60°C; Psyngas = 10 bar), mainly with formation of isomerization products. Keywords: Calophyllum inophyllum oil, hydroformylation, internal olefins, ionic liquids, methyl oleate, microwave, phosphite, renewable heterogeneous catalysts, rhodium, transesterification.

One-pot synthesis of multisubstituted imidazoles under solvent-free conditions and microwave irradiation using Fe3O4@SiO2–imid–PMAnmagnetic porous nanospheres as a recyclable catalyst

Synthesis of substituted imidazoles using the Fe3O4@SiO2–imid–PMAnnanocatalyst.

ChemInform Abstract: Ultrasound‐Assisted Synthesis of 6‐Methyl‐1,2,3,4‐tetrahydro‐N‐aryl‐2‐oxo/thio‐4‐arylpyrimidine‐5‐carboxa mides Catalyzed by Uranyl Nitrate Hexahydrate.

AbstractThe reaction can also be run under conventional heating conditions resulting in longer reaction times and slightly lower yields.

Synthesis of Phenanthridine Derivatives Functionalized in the C‐Ring by Means of IMDAF Reactions under Microwave or Conventional Heating Conditions

AbstractPhenanthridines functionalized in the C‐ring have been synthesized by IMDAF (intramolecular Diels–Alder reaction on furans) cyclization of ortho‐furyl(alkenylamino)arenes under both microwave and conventional heating conditions. The outcomes of the reactions are highly dependent on the substitution patterns both on the dienophile and on the arene components. 5,6‐Dihydrophenanthridines, which can easily be oxidized to fully aromatic phenanthridines, are formed under microwave conditions as long as the Diels–Alder adduct contains a hydrogen atom in the 6a‐position. Aromatization of the phenanthridine C‐ring does not occur when the cyclization is performed under conventional heating conditions. The IMDAF reaction can, under these conditions, lead to Diels–Alder adducts or to phenanthridines with partially saturated and functionalized C‐rings, depending on the detailed structure of the starting material.

CN Bond Formation Using Highly Effective and Reusable Nickel Ferrite Nanoparticles in Water

AbstractNickel ferrite nanoparticles were used as a catalyst system for CN bond formation in water under conventional heating conditions. These nanoparticles were synthesized by using the coprecipitation method and were analyzed by using TEM, SEM, XRD, X‐ray fluorescence, and FTIR techniques. The magnetization behavior of nanoparticles was also investigated by measuring the hysteresis curve of the sample, which confirmed the superparamagnetic nature of the catalyst. By using this catalyst system, various types of amines and amides, including primary and secondary ones, can react with different types of aryl halides. In addition, it is a recyclable and reusable catalyst system with high turnover efficiency. The reactions proceed in water as a green solvent, which result in good to excellent yields in short times.

ChemInform Abstract: Domino 1,3‐Dipolar Cycloadditions of N‐Alkyl‐α‐Amino Esters with Paraformaldehyde: A Direct Access to α‐Hydroxymethyl α‐Amino Acids.

AbstractThe reaction of the aminoesters with paraformaldehyde can proceed under conventional heating or microwave‐assisted conditions.

ChemInform Abstract: Highly Regioselective Diels—Alder Reaction of 9‐Substituted Anthracenes with Citraconic Anhydride.

The regioselectivity in the Diels–Alder reaction of 9-substituted anthracenes having electron-releasing substituents with citraconic anhydride has been investigated. The ortho regioisomer is preferred in all the cases with good yield. The reaction proceeded best under conventional heating conditions in toluene.

Highly active recyclable heterogeneous nanonickel ferrite catalyst for cyanation of aryl and heteroaryl halides

Magnetic nickel ferrite nanoparticles are found to be an efficient catalytic system for cyanation reactions of various types of aryl halides under conventional heating conditions. All the reactions result in very good to excellent yields under optimized reaction conditions. Furthermore, the catalyst is easily removed from the reaction medium and can be reused further in several subsequent runs. Copyright © 2014 John Wiley & Sons, Ltd.

ChemInform Abstract: A Short and Efficient Synthesis of Honokiol via Claisen Rearrangement.

AbstractClaisen rearrangement of bis‐O‐allylbiphenyl provides mixtures of honokiol (II) and isohonokiol (III) under both conventional and microwave heating conditions.

ChemInform Abstract: Solvent‐Free and Catalysts‐Free Chemistry: A Benign Pathway to Sustainability

AbstractReview: [121 refs.

ChemInform Abstract: Synthesis of Highly Basic Hexasubstituted Biguanides by Environmentally Friendly Methods.

AbstractVarious methods such as high speed vibrational milling, high pressure, ultrasound, microwave irradiation, and conventional heating conditions are employed for the reaction of tetramethylguanidine with carbodiimides.