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Conventional Heating (conventional + heating)
Selected AbstractsDIFFUSION OF BEET DYE DURING ELECTRICAL AND CONVENTIONAL HEATING AT STEADY-STATE TEMPERATURE,JOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2001MARYBETH LIMA ABSTRACT Ohmic heating has been shown to alter mass transfer properties of fruit and vegetable tissue. Diffusion of beet dye from beetroot tissue into a fluid was studied during conventional and ohmic heating as a function of steady-state temperature. The volume of beet dye diffusing into solution during ohmic heating was enhanced with respect to conventional heating at 42C and 58C, but not at 72C. This can be explained by examining the differences in electrical conductivity of beet tissue at these temperatures during conventional and ohmic heating. At 42 and 58C, the electrical conductivity of beet tissue heated ohmically is higher than the electrical conductivity of beet tissue heated conventionally. At 72C, the electrical conductivities of beet tissue during conventional and ohmic heating are equal. The extent of diffusion in the ohmic case is also positively correlated with applied voltage. These results suggest that food processes involving mass transfer can be enhanced by choosing conditions in which the electrical conductivity of a sample under ohmic conditions is maximized. [source] Palladium-Catalyzed Direct Arylations of 1,2,3-Triazoles with Aryl Chlorides using Conventional HeatingADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2008Lutz Ackermann Abstract Generally applicable, palladium-catalyzed direct arylations of 1,2,3-triazoles with aryl chlorides were accomplished through conventional heating at reaction temperatures of 105,120,°C. Thereby, intra- and intermolecular CH bond functionalizations were achieved with a variety of differently substituted chlorides as electrophiles, bearing numerous valuable functional groups. [source] 2-Aryl-3-(1H -Azol-1-yl)-1H -Indole Derivatives: A New Class of Antimycobacterial Compounds , Conventional Heating in Comparison with MW-Assisted SynthesisARCHIV DER PHARMAZIE, Issue 12 2009Daniele Zampieri Abstract 2-Aryl-3-(1H -imidazol-1-yl and 1H -1,2,4-triazol-1-yl)-1H -indole derivatives were synthesized and tested for their in-vitro antifungal and antimycobacterial activities. These indole derivatives were devoid of antifungal activity against the tested strains of Candida spp. Yet, they exhibited an interesting antitubercular activity against Mycobacterium tuberculosis reference strain H37Rv. [source] Biaryl Peptides from 4-Iodophenylalanine by Solid-Phase Borylation and Suzuki,Miyaura Cross-CouplingEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2010Ana Afonso Abstract Resin-bound phenylalanine boronates were prepared by solid-phase Miyaura borylation of 4-iodophenylalanine peptides. Subsequent arylation through a Suzuki,Miyaura cross-coupling was carried out using a variety of aryl halides under conventional heating and under microwave irradiation. Microwaves greatly enhanced the arylation, shortening thereaction time and providing the biaryl peptides in higherpurities. [source] Eco-friendly methodologies for the synthesis of some aromatic esters, well-known cosmetic ingredientsINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 1 2005C. Villa Synopsis Solid,liquid solvent-free phase transfer catalysis (PTC) and acidic catalysis in dry media were applied, with noticeable improvement and simplification over classical procedures in a Green Chemistry context, to the synthesis of some aromatic esters useful as cosmetic ingredients: 3-methylbutyl 4-methoxycinnamate, 2-ethylhexyl 4-methoxycinnamate, 2-ethylhexyl 4-(dimethylamino)benzoate and 2-ethylhexyl salicylate, well-known ultraviolet B sunscreen filters; 4-isopropylbenzyl salicylate, UV absorber and cutaneous antilipoperoxidant; propyl 4-hydroxybenzoate and butyl 4-hydroxybenzoate (parabens), antimicrobial agents. The reactions were performed under microwave (MW) activation and conventional heating. The best results for the synthesis of cinnamic, salicylic and 4-(dimethylamino)benzoic esters were achieved by in situ preformed carboxylates alkylation with alkyl bromides using PTC. The 4-hydroxybenzoates were obtained in good yields by classical esterification of the acid with alcohols using a simple heterogeneous mixture of reagents with catalytic amounts of p -toluenesulfonic acid (PTSA). The comparisons of yields and thermal profiles under either MW or conventional heating were studied and reported. Résumé La catalyse par transfert de phase (CTP) solide-liquide sans solvant et l'estérification acido-catalysée en ,,milieu sec'' ont été appliquées, dans le cadre de la ,,chimie verte'', avec des nettes améliorations et simplifications par rapport aux méthodes classiques, à la synthèse de certains esters aromatiques, ingrédients cosmétiques: 3-methylbutyl 4-méthoxycinnamate, 2-éthylhéxyl 4-méthoxycinnamate, 2-éthylhéxyl 4-(diméthylamino) benzoate et 2-éthylhéxyl salicylate, filtres solaires UVB bien connus; 4-isopropylbenzyl salicylate, filtre UV et antilipopéroxydant cutané; propyl 4-hydroxybenzoate et butyl 4-hydroxybenzoate (parabens), agents antimicrobien. Les réactions ont été procédées sous irradiation micro-onde et par chauffage classique. Pour la synthèse des esters dérivés de l'acide cinnamique, salicylique et 4-(diméthylamino)benzoïque les meilleurs résultats ont été obtenus grâce à la CTP par alkylation des carboxylates (préformés in situ) avec des bromures d'alkyle. Les esters de l'acide 4-hydroxybenzoique ont été obtenus avec de bons rendements par simple mélange hétérogène des réactifs et d'acide p-toluènesulfonique (PTSA) comme catalyseur. Les rendements et les profils de montée en température sous micro-ondes et par chauffage classique ont été comparés. [source] Green chemistry procedure for the synthesis of cyclic ketals from 2-adamantanone as potential cosmetic odourantsINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 5 2002M. T. Genta Synopsis Some cyclic ketals derived from 2-adamantanone were obtained in excellent yields by microwave activation under solvent-free conditions, as a ,green chemistry' procedure. A number of experiments were performed to evaluate the most efficient catalytic conditions. The best results were obtained using a simple heterogeneous mixture of reagents and p -toluenesulphonic acid as the catalyst, without any solvent or support. The data are reported and compared with those obtained by other microwave-mediated syntheses or by classical method. In order to check the possible intervention of non-thermal microwave effects, the best experiment in ,dry media' was carried out with considerable lower yield by conventional heating, in a thermostated oil bath, under the same conditions as under microwaves (time, temperature and vessel). All the synthesized compounds were tested for their olfactive character and for a potential cosmetic use. The odour evaluation is reported. Résumé Des acétals cycliques dérivés de la 2-adamantanone ont été obtenus sous irradiation microonde sans solvant avec d'excellents rendements selon un procédé de ,chimie verte'. Un certain nombre d'experiences ont été réalisées pour optimiser les conditions de réaction. Les résultats obtenus par simple mélange hétérogène des réactifs et de l'acide p -toluènesulphonique 10% (p/p) comme catalyseur ont été décrits et comparés avec ceux obtenus avec les autres procédés, sous irradiation microonde ou par chauffage traditionnel. Dans le but de mettre en évidence l'éventuelle intervention d'effets spécifiques (non-purement thermiques) des microondes, la meilleure réaction obtenue en ,milieu sec' a été effectuée, avec des rendements nettement plus faibles, dans les mêmes conditions (temps et température), par chauffage classique. Les propriétés olfactives de tous les produits obtenus ont été déterminées pour évaluer une possible utilization cosmétique. [source] A review on microwave baking of foodsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 2 2001Gülüm Sumnu Summary Microwaves interact with polar molecules and charged particles of food to generate heat. There are differences between the heating mechanisms of microwave and conventional heating. The use of microwave heating has the advantage of saving energy and time, improving both nutritional quality and acceptability of some foods by consumers. Microwave ovens are successfully used both in homes and in the food service industry. However, there are still problems in perfecting microwave baking, therefore it is a popular research area. The main problems found to occur in microwave-baked food products are low volume, tough or firm texture, lack of browning and flavour development. Recent studies aim to improve the quality of microwave-baked products. This article reviews the basic principles of microwave baking, problems commonly occurring in microwave-baked products and finally studies published concerning microwave-baked products. [source] Palladium-Catalyzed Direct Arylations of 1,2,3-Triazoles with Aryl Chlorides using Conventional HeatingADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2008Lutz Ackermann Abstract Generally applicable, palladium-catalyzed direct arylations of 1,2,3-triazoles with aryl chlorides were accomplished through conventional heating at reaction temperatures of 105,120,°C. Thereby, intra- and intermolecular CH bond functionalizations were achieved with a variety of differently substituted chlorides as electrophiles, bearing numerous valuable functional groups. [source] Viscosity behavior of microwave-heated and conventionally heated poly(ether sulfone)/dimethylformamide/lithium bromide polymer solutionsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Ani Idris Abstract This article investigates the viscosity behavior of new membrane dope solutions of poly(ether sulfone) (PES) and dimethylformamide with low-molecular-weight halogenated lithium bromide (LiBr) additives prepared with two different techniques: (1) a microwave (MW) technique and (2) a conventional heating (CH) technique. In addition, the influence of different concentrations of anhydrous halogenated LiBr additives (0,5 wt %) on the viscosity behavior is analyzed. The viscosity of the dope solutions was assessed with a conical rheometer equipped with a high-viscosity adapter. The results revealed that the pure PES solutions prepared by the MW and CH techniques exhibited pseudoplastic and Newtonian behavior, respectively. Both the MW and CH PES solutions containing the LiBr additives exhibited dilatant behavior, which obeyed the power law. The apparent viscosity of all the dope solutions prepared with the MW technique was lower than that of those prepared with the CH technique. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Combining microwave and ultrasound irradiation for rapid synthesis of nanowires: a case study on Pb(OH)BrJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2009Xiao-Fang Shen Abstract BACKGROUND: One-dimensional (1D) nanostructures such as wires, tubes and belts have attracted much attention in recent years because of their fascinating properties and promising applications, and various methods have been developed to prepare 1D nanostructures. Microwave and ultrasound, two methodologies for rapid synthesis, have both been applied to fabricate nanostructures. This paper reports on combining microwave and ultrasound irradiation as a new strategy for rapid synthesis of nanowires. Using Pb(OH)Br as a study case, nanowires were rapidly synthesized under the combined irradiation. The use of the ionic liquid 1-butyl-3-methylimidazolium bromide as a structure-directing agent and microwave absorbent significantly simplified the preparation procedure. RESULTS: Combined microwave,ultrasound irradiation at (50 W,50 W) greatly reduced the reaction time (10 min) and significantly increased the product yield (45.0%) in comparison with conventional heating (24 h reaction time, 23.0% yield). Combined microwave,ultrasound irradiation at (50 W,50 W) also changed the resultant wires from 20,30 µm diameter and 2,3 mm long to 80,800 nm and 50,100 µm, respectively. Further increase in power of the combined irradiation (250 W,50 W) led to a dramatic reduction in the reaction time (80 s) with a slightly increased yield of 48.2%. CONCLUSIONS: The obvious advantages of combined microwave,ultrasound irradiation are marked improvement of the product yield, significant enhancement of reaction rate and increased aspect ratio of the 1D structure. Copyright © 2009 Society of Chemical Industry [source] Synergism of microwave irradiation and enzyme catalysis in synthesis of isoniazidJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2007Ganapati D Yadav Abstract Isoniazid is a useful antitubercular drug widely employed in combination therapy with rifampicin. The synthesis of isoniazid from ethyl isonicotinate and hydrazine hydrate was studied in non-aqueous media via lipase-catalyzed hydrazinolysis under both conventional heating and microwave irradiation by using different supported lipases. Among three different commercial lipases used, namely Novozym 435 (Candida antarctica lipase), Lipozyme RM IM (Rhizomucor miehei lipase) and Lipozyme TL IM (Thermomyces lanuginosus lipase), Novozym 435 was found to be the most effective, with conversion of 54% for equimolar concentrations at 50 °C in 4 h. The rate of reaction as well as final conversion increased synergistically under microwave irradiation in comparison with conventional heating, which showed 36.4% conversion, even after 24 h, for the control experiment. Effects of various process parameters such as speed of agitation, catalyst loading, substrate concentration, product concentration and temperature were studied. A kinetic model is also described. Copyright © 2007 Society of Chemical Industry [source] DIFFUSION OF BEET DYE DURING ELECTRICAL AND CONVENTIONAL HEATING AT STEADY-STATE TEMPERATURE,JOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2001MARYBETH LIMA ABSTRACT Ohmic heating has been shown to alter mass transfer properties of fruit and vegetable tissue. Diffusion of beet dye from beetroot tissue into a fluid was studied during conventional and ohmic heating as a function of steady-state temperature. The volume of beet dye diffusing into solution during ohmic heating was enhanced with respect to conventional heating at 42C and 58C, but not at 72C. This can be explained by examining the differences in electrical conductivity of beet tissue at these temperatures during conventional and ohmic heating. At 42 and 58C, the electrical conductivity of beet tissue heated ohmically is higher than the electrical conductivity of beet tissue heated conventionally. At 72C, the electrical conductivities of beet tissue during conventional and ohmic heating are equal. The extent of diffusion in the ohmic case is also positively correlated with applied voltage. These results suggest that food processes involving mass transfer can be enhanced by choosing conditions in which the electrical conductivity of a sample under ohmic conditions is maximized. [source] EFFECTS OF THERMAL AND ELECTROTHERMAL PRETREATMENTS ON HOT AIR DRYING RATE OF VEGETABLE TISSUEJOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2000WEI-CHI WANG ABSTRACT Cylindrical samples of carrot, potato and yam were dried in a hot-air dehydrator after preheating to 50C or 80C by three different heating methods (conventional, microwave and ohmic). The results showed that enhancement of drying rate increased with pretreatment temperature. Ohmic pretreatment increased the drying rate more than conventional and microwave heating. Desorption isotherms showed that in the low aw range, desorption data of preheated and raw materials were similar. However, the isotherms of preheated samples shifted when aw was high, which indicated that thermal pretreatments altered the structure, and apparently, the water distribution within these materials. For all samples, ohmic pretreatment showed stronger influences on isotherms than microwave heating, while the pretreatment effect of conventional heating was only observed for potato tissue. [source] Extraction Using Moderate Electric FieldsJOURNAL OF FOOD SCIENCE, Issue 1 2004I. SENSOY ABSTRACT: During moderate electric field (MEF) processing, a voltage applied across a food material may affect the permeability of cell membranes. It is known that high electric fields can cause either reversible or irreversible rupture of cell membranes. In this research, the effect of MEF processing on permeability was studied. Effects of frequency and electric field strength were investigated. Cellular structure was investigated by transmission electron microscopy (TEM). Fermented black tea leaves and fresh or dry mint leaves were placed in tea bags or cut in 1 cm2 squares, depending on the experiment, and immersed in an aqueous fluid medium. Control samples were heated on a hot plate. MEF treatments were conducted by applying a voltage across electrodes immersed in opposite sides of the beaker. Control and MEF-treated fresh mint leaf samples heated to 50°C were analyzed by TEM. MEF processing significantly increased the extraction yield for fresh mint leaves because of additional electric field effects during heating. Dried mint leaves and fermented black tea leaves were not affected by the treatment type. Low frequency resulted in higher extraction rates for fresh mint leaves. The electric field strength study showed that electrical breakdown is achieved even at low electric field strengths. MEF treatment shows potential to be used as an alternative to conventional heating for extraction from cellular materials. [source] Preparation of 5-nitro-2-amino[b]thiophenes and 1-(2-amino-5-nitrophenyl)ethanones via microwave irradiationJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2009Afsha Rais 1-(2-Chloro-5-nitrophenyl)ethanone) reacts with various amines in the presence of sulfur under microwave radiation to give the corresponding 2-aminobenzo[b]-thiophenes 3a,f in good yields. The yields of 3a,f are vastly superior to those obtained using conventional heating. Additionally, 1-(2-amino-5-nitrophenyl)ethanones 4a,f were also obtained. A mechanism is proposed in which 2-amino thiophenes 3a,f are formed by a SNAr mechanism involving an intramolecular addition of sulfur of the intermediate thioamide to the 2-substituted carbon to give a Meisenheimer complex, which collapses to 2-aminothiophenes 3a,f, and 2-amino ketones (4a,f) are formed by a parallel pathway involving nucleophilic addition amine to the 2-chloro position of 1 to form a Meisensheimer complex, which collapses to the amino ethanones. J. Heterocyclic Chem., (2009). [source] Sulfamic acid catalyzed one-pot synthesis of 2,5-diaryl-1,3,4-oxadiazoles under microwave irradiation and conventional heatingJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2009J. Venu Madhav Sulfamic acid has been found to be an efficient catalyst for the one-pot synthesis of novel 2,5-diaryl-1,3,4-oxadiazoles by condensation of different coumarinoyl hydrazides with various coumarinoyl or quinolinoyl chlorides under microwave irradiation and conventional heating. Some of the advantages of this method are low reaction times, operational simplicity, and high yields. J. Heterocyclic Chem., (2009) [source] Syntheses of oxazolo[4,5- c]pyridine and 6-azaindoleJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2008Freddy Tjosaas The preparation of oxazolo[4,5- c]pyridine and 6-azaindole from 4-bromo-3-pivaloylaminopyridine (8) is reported. The oxazolopyridine 2- tert -butyl-oxazolo[4,5- c]pyridine (9) was successfully prepared from 8 in 78% yield by a new base/TBAB promoted non-catalyzed microwave cyclisation strategy (10 min) or, alternatively, in 54% yield by conventional heating (48 hrs) and CuI catalysis. The 6-azaindole 2-phenyl-1-(trimethylacetyl)-6-azaindole (13) was prepared from 8 in a two step procedure, including a Sonogashira coupling reaction. [source] Synthesis of 4-[18F]fluoroiodobenzene and its application in sonogashira cross-coupling reactionsJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 8 2003Frank R. Wüst Abstract The first application of a Sonogashira cross-coupling reaction in 18F chemistry has been developed. The reaction was exemplified by the cross-coupling of terminal alkynes (ethynylcyclopentyl carbinol 6, 17,-ethynyl-3,17,-estradiol 7 and 17,-ethynyl-3-methoxy-3,17,-estradiol 8) with 4-[18F]fluoroiodobenzene. 4,4,-Diiododiaryliodonium salts were used as precursors for the synthesis of 4-[18F]fluoroiodobenzene, enabling the convenient access to 4-[18F]fluoroiodobenzene in 13,70% yield using conventional heating or microwave activation. The Sonogashira cross-coupling of 4-[18F]fluoroiodobenzene with terminal alkynes gave the corresponding 4-[18F]fluorophenylethynyl-substituted compounds [18F]-9, [18F]-10 and [18F]-13 in yields up to 88% within 20 min of starting from 4-[18F]fluoroiodobenzene. Copyright © 2003 John Wiley & Sons, Ltd. [source] Ortho -[18F]Fluoronitrobenzenes by no-carrier-added nucleophilic aromatic substitution with K[18F]F,K222,A comparative studyJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 13 2002M. Karramkam Abstract The scope of the nucleophilic aromatic ortho -fluorinations from the corresponding ortho -halonitrobenzene precursors (halo-to-fluoro substitutions) with no-carrier-added [18F]fluoride ion as its activated K[18F]F,K222 complex has been evaluated via the radiosynthesis of ortho -[18F]fluoronitrobenzene, chosen as a model reaction. The parameters studied include the influence of the leaving group in the ortho position of the phenyl ring (,Cl, ,Br, ,l), the quantity of precursor used, the type of activation (conventional heating or microwave irradiations), the solvent, the temperature and the reaction time. The iodo-precursor was completely unreactive and the bromo-precursor gave only low incorporation (<10%) in the optimal conditions used (conventional heating at 145°C or microwave activation, 100 W for 120 s). Only the chloro-precursor was found reactive in the conditions described above and up to 70% yield was observed for the formation of ortho -[18F]fluoronitrobenzene ([18F]- 1). In all the experiments, the unwanted ortho -[18F]fluoro-halobenzenes, potentially resulting from the nitro-to-fluoro substitution, could not be detected. These results will be applied for the radiosynthesis of 5-[18F]fluoro-6-nitroquipazine, a potent radioligand for the imaging of the serotonin transporter with PET. Copyright © 2002 John Wiley & Sons, Ltd. [source] Microwave-assisted solid-phase peptide synthesis at 60 °C: alternative conditions with low enantiomerization,JOURNAL OF PEPTIDE SCIENCE, Issue 12 2009Carina Loffredo Abstract Several conditions have been used in the coupling reaction of stepwise SPPS at elevated temperature (SPPS-ET), but we have elected the following as our first choice: 2.5-fold molar excess of 0.04,0.08 M Boc or Fmoc-amino acid derivative, equimolar amount of DIC/HOBt (1:1) or TBTU/DIPEA (1:3), 25% DMSO/toluene, 60 °C, conventional heating. In this study, aimed to further examine enantiomerization under such condition and study the applicability of our protocols to microwave-SPPS, peptides containing L -Ser, L -His, L -Cys and/or L -Met were manually synthesized traditionally, at 60 °C using conventional heating and at 60 °C using microwave heating. Detailed assessment of all crude peptides (in their intact and/or fully hydrolyzed forms) revealed that, except for the microwave-assisted coupling of L -Cys, all other reactions occurred with low levels of amino acid enantiomerization (<2%). Therefore, herein we (i) provide new evidences that our protocols for SPPS at 60 °C using conventional heating are suitable for routine use, (ii) demonstrate their appropriateness for microwave-assisted SPPS by Boc and Fmoc chemistries, (iii) disclose advantages and limitations of the three synthetic approaches employed. Thus, this study complements our past research on SPPS-ET and suggests alternative conditions for microwave-assisted SPPS. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd. [source] Microwave-assisted derivatization of cellulose in an ionic liquid: An efficient, expedient synthesis of simple and mixed carboxylic estersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2010Shirley Possidonio Abstract Microwave (MW)-assisted cellulose dissolution in ionic liquids (ILs) has routinely led either to incomplete biopolymer solubilization, or its degradation. We show that these problems can be avoided by use of low-energy MW heating, coupled with efficient stirring. Dissolution of microcrystalline cellulose in the IL 1-allyl-3-methylimidazolium chloride has been achieved without changing its degree of polymerization; regenerated cellulose showed pronounced changes in its index of crystallinity, surface area, and morphology. MW-assisted functionalization of MCC by ethanoic, propanoic, butanoic, pentanoic, and hexanoic anhydrides has been studied. Compared with conventional heating, MW irradiation has resulted in considerable decrease in dissolution and reaction times. The value of the degree of substitution (DS) was found to be DSethanoate > DSpropanoate > DSbutanoate. The values of DSpentanoate and DShexanoate were found to be slightly higher than DSethanoate. This surprising dependence on the chain length of the acylating agent has been reported before, but not rationalized. On the basis of the rate constants and activation parameters of the hydrolysis of ethanoic, butanoic, and hexanoic anhydrides in aqueous acetonitrile (a model acyl transfer reaction), we suggest that this result may be attributed to the balance between two opposing effects, namely, steric crowding and (cooperative) hydrophobic interactions between the anhydride and the cellulosic surface, whose lipophilicity has increased, due to its partial acylation. Four ethanoate-based mixed esters were synthesized by the reaction with a mixture of the two anhydrides; the ethanoate moiety predominated in all products. The DS is reproducible and the IL is easily recycled. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 48: 134,143, 2010 [source] Evidence for the Microwave Effect During the Annealing of Zinc OxideJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2007J. Binner A microwave/conventional hybrid furnace has been used to anneal virtually fully dense zinc oxide ceramics under pure conventional and a microwave/conventional hybrid heating regime with a view to obtaining evidence for the "microwave effect" during the resulting grain growth. In each case it was ensured that each sample within a series had an identical thermal history in terms of its temperature/time profile. The results showed that grain growth was enhanced during hybrid heating compared with pure conventional heating; the greatest enhancement, a factor of ,3 increase in average grain size, was observed in the range 1100°,1150°C. The grain growth exponent decreased from 3 during conventional heating to 1.4 during hybrid heating in this temperature range, suggesting an acceleration of the diffusional processes involved. Temperature gradients within the samples were found to be too small to explain the results. This suggests that clear evidence has been found to support the existence of a genuine "microwave effect." [source] Preparation of Poly(, -caprolactone)/Clay Nanocomposites by Microwave-Assisted In Situ Ring-Opening PolymerizationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 10 2007Liqiong Liao Abstract PCL/clay nanocomposites were prepared by microwave-assisted in situ ROP of , -caprolactone in the presence of either unmodified clay (Cloisite® Na+) or clay modified by quaternary ammonium cations containing hydroxyl groups (Cloisite 30B). This PCL showed significantly improved monomer conversion and molecular weight compared with that produced by conventional heating. An intercalated structure was observed for the PCL/Cloisite Na+ nanocomposites, while a predominantly exfoliated structure was observed for the PCL/Cloisite 30B nanocomposites. Microwave irradiation proved to be an effective and efficient method for the preparation of PCL/clay nanocomposites. [source] Microwave-Assisted Synthesis of PLLA-PEG-PLLA Triblock CopolymersMACROMOLECULAR RAPID COMMUNICATIONS, Issue 4 2007Chao Zhang Abstract Poly(L -lactide)- block -poly(ethylene glycol)- block -poly(L -lactide) (PLLA-PEG-PLLA) triblock copolymers were synthesized effectively by poly(ethylene glycol) initiated ring-opening polymerization (ROP) of L -lactide under microwave irradiation. The products were characterized by 1H NMR, GPC, and DSC. The experimental results have demonstrated that PLLA-PEG-PLLA triblock copolymer with a number-average molar mass of 28,230 g,·,mol,1 and an L -lactide conversion of 92.4% could be synthesized after the L -lactide/PEG2000 reaction mixture was irradiated for 3 min at 100,°C. The L -lactide/PEG feed ratio had a strong influence on the microwave-assisted ring-opening polymerization, in which higher L -lactide/PEG feed ratios led to copolymers with higher molar masses and lower L -lactide conversions. Prolonged microwave irradiation at 100,°C did not change the molar mass of the copolymers significantly. The DSC study indicated that higher glass transition and melting temperatures were obtained for PLLA-PEG-PLLA triblock copolymers with longer PLLA segment length. The synthesis of the triblock copolymers via microwave heating was much faster than via conventional heating. [source] Microwave-Assisted Free Radical Copolymerizations of Styrene and Methyl MethacrylateMACROMOLECULAR RAPID COMMUNICATIONS, Issue 4 2007Heiner Stange Abstract Free radical copolymerizations of styrene and MMA were performed in toluene and DMF as solvents using different peroxide initiators with and without microwave irradiation. A general trend showed significant solvent dependence of monomer conversion rate only for copolymerizations initiated by tert -butyl perbenzoate in DMF compared to toluene but nearly no impact for copolymerizations initiated by dicumyl peroxide and dibenzoyl peroxide. Significant variations in copolymer composition were not observed for reactions under conventional heating compared to microwave irradiation. It was concluded that enhanced initiator decomposition under microwave irradiation in DMF accelerate polymerization of styrene and MMA by formation of larger amount of initiator radicals. [source] Microwave-Assisted Polymer Synthesis: State-of-the-Art and Future PerspectivesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2004Frank Wiesbrock Abstract Summary: Monomodal microwaves have overcome the safety uncertainties associated with the precedent domestic microwave ovens. After fast acceptance in inorganic and organic syntheses, polymer chemists have also recently discovered this new kind of microwave reactor. An almost exponential increase of the number of publications in this field reflects the steadily growing interest in the use of microwave irradiation for polymerizations. This review introduces the microwave systems and their applications in polymer syntheses, covering step-growth and ring-opening, as well as radical polymerization processes, in order to summarize the hitherto realized polymerizations. Special attention is paid to the differences between microwave-assisted and conventional heating as well as the "microwave effects". Results of search on number of publications on microwave-assisted polymerizations, sorted by year. [source] Intramolecular phenylborane complexes with monobasic bidentate Schiff basesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 2 2007Shweta Gaur Abstract A series of intramolecular complexes with Schiff base ligands having N,S and N,O donor systems were synthesized in an open vessel under microwave irradiation (MWI) using a domestic microwave oven. The reaction time has been brought down from hours to seconds with improved yield as compared with the conventional heating. The complexes have been characterized on the basis of elemental analysis, conductance measurements and spectroscopic analysis. Based on the IR, 1H NMR, 11B NMR and 13C NMR spectroscopic studies, a tetrahedral geometry has been proposed for the resulting complexes. The compounds have been screened in vitro against bacteria and fungi to test their antimicrobial property and in vivo in male albino rats to test their antifertility property. The testicular sperm density, motility and density of cauda epididymal spermatozoa along with biochemical parameters of reproductive organs have been examined and discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Microwave-Assisted Covalent Sidewall Functionalization of Multiwalled Carbon NanotubesCHEMISTRY - A EUROPEAN JOURNAL, Issue 14 2006Junxin Li Dr. Abstract Thermal cycloaddition of 1,3-dipolar azomethine ylides to the sidewalls of multiwalled carbon nanotubes (MWNTs) has been used to prepare MWNTs that contain 2-methylenethiol-4-(4-octadecyloxyphenyl) (4), N -octyl-2-(4-octadecyloxyphenyl) (5) or 2-(4-octadecyloxyphenyl)pyrrolidine (6) units. All these contain the 4-octadecyloxyphenyl substituent that acts as a solubilizing group. Microwave (MiW)-assisted heating was found to be highly efficient for soluble MWNTs, for which the amount of added groups after only 2 h of MiW heating at 200,°C, determined by using thermogravimetric analysis, was found to be in the same range as that obtained after 100,120 h of conventional heating of soluble and insoluble MWNTs. Solubility is a key feature for a successful MiW-heated reaction; MWNTs insoluble in the reaction medium yielded considerably less addends in the MiW-heated reactions than in the conventionally heated reaction. The location and even distribution of the pyrrolidine units over the outermost layer of the MWNTs was verified by transmission electron microscopy analysis of 4 that had been treated with gold nanoparticles and thoroughly washed to remove gold particles adsorbed on nonfunctionalized parts of the MWNTs. [source] Infrared Heating in Food Processing: An OverviewCOMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY, Issue 1 2008Kathiravan Krishnamurthy ABSTRACT:, Infrared (IR) heating provides significant advantages over conventional heating, including reduced heating time, uniform heating, reduced quality losses, absence of solute migration in food material, versatile, simple, and compact equipment, and significant energy saving. Infrared heating can be applied to various food processing operations, namely, drying, baking, roasting, blanching, pasteurization, and sterilization. Combinations of IR heating with microwave heating and other common conductive and convective modes of heating have been gaining momentum because of increased energy throughput. This article reviews aspects of IR heating and presents a theoretical basis for IR heat processing of food materials and the interaction of IR radiation with food components. The effect of IR on food quality attributes is discussed in the context of samples and process parameters. Applications of IR heating in food processing operations and future research potential are also reviewed. [source] | ||||||||||||||||||||||||||||