Microwave Irradiation
Mostrando 13-24 de 90 artigos, teses e dissertações.
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13. Selective Synthesis of (Z)-Chalcogenoenynes and (Z,Z)-1,4-bis-Chalcogenbuta-1,3-dienes Using PEG-400
We present here our results on the temperature controlled, selective hydrochalcogenation of 1,4-diorganyl-1,3-butadiynes with nucleophilic species of selenium, tellurium and sulfur generated in situ from the respective diaryl dichalcogenide and NaBH4. Using polyethylene glycol (PEG)-400 at 30 ºC the (Z)-chalcogenoenynes are obtained and at 90 ºC the (Z,Z)-
J. Braz. Chem. Soc.. Publicado em: 2016-11
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14. PREPARAÇÃO DE 1,2,4-OXADIAZOL: SEQUÊNCIA DIDÁTICA APLICADA EM DISCIPLINA DE SÍNTESE ORGÂNICA NA GRADUAÇÃO
1,2,4-oxadiazoles are used in a wide range of applications, including medicinal chemistry and chemistry of materials. However, this kind of oxadiazoles is not usually prepared in an undergraduate organic teaching laboratory. This work describes a didactic sequence for the preparation of 1,2,4-oxadiazols, mediated by microwave irradiation, employing home-use
Quím. Nova. Publicado em: 2016-09
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15. Microwave Assisted Combustion Synthesis and Characterization of Nanocrystalline Nickel-doped Cobalt Ferrites
Abstract Nanoparticles nickel-doped cobalt ferrites [NixCo1-xFe2O4 (x = 0.0, 0.25, 0.50, 0.75 and 1.0 of Ni2+)] were prepared by the microwave combustion synthesis, using a stoichiometric mixture of metal nitrates and urea as the oxidizer and fuel to drive the reaction. The effect of microwave irradiation on the phase composition was favorable to promote the
Mat. Res.. Publicado em: 01/08/2016
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16. Generation of Volatile Compounds from Carotenoids of Dunaliella bardawil Algae by Water Bath Heating and Microwave Irradiation
The volatile compounds formed by thermal degradation of the carotenoids present in Dunaliella bardawil were investigated by microwave irradiation (MW) and water bath heating (WB) in different conditions of temperature and time using central composite design. Volatiles extraction by solid phase microextraction (SPME) was optimized and performed at 40 °C for
J. Braz. Chem. Soc.. Publicado em: 2016-08
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17. PRODUÇÃO DE BIODIESEL A PARTIR DE ÁCIDOS GRAXOS PROVENIENTES DO REFINO DE ÓLEOS VEGETAIS VIA CATÁLISE ÁCIDA HETEROGENEA E MICRO-ONDAS
This work presents the biofuel production results of the esterification of fatty acids (C12-C18) and high-acid-content waste vegetable oils from different soap stocks (soybean, palm, and coconut) with methanol, ethanol, and butanol by acid catalysis. We used Amberlyst-35 (A35) sulfonic resin as a heterogeneous acid catalyst and p-toluenesulfonic acid as a ho
Quím. Nova. Publicado em: 2015-12
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18. Synthesis of 3-(1H-1,2,3-Triazol-1-yl)-2-(arylselanyl)pyridines by Copper-Catalyzed 1,3-Dipolar Cycloaddition of 2-(Arylselanyl)-3-azido-pyridines with Terminal Alkynes
We present here our results in the synthesis of eleven new 3-(1H-1,2,3-triazol-1-yl)-2-(arylselanyl)pyridines by copper-catalyzed azide-alkyne cycloaddition reactions. The reactions were performed in the presence of catalytic amount of copper(II) acetate and sodium ascorbate using a mixture of tetrahydrofuran/water (1:1) as solvent at room temperature in air
J. Braz. Chem. Soc.. Publicado em: 2015-11
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19. Microwave-assisted extraction of anthocyanin from Chinese bayberry and its effects on anthocyanin stability
AbstractAnthocyanins are present in high concentrations in Chinese bayberry, Myrica rubra Sieb. & Zucc. Herein, a microwave-assisted extraction was used to extract the anthocyanins from Chinese bayberry. The HPLC chromatogram of the extracts showed that the anthocyanin components were slightly hydrolysed during the extraction process. Further experiments con
Food Sci. Technol. Publicado em: 15/09/2015
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20. REAÇÃO DE CONDENSAÇÃO DO GLICEROL COM COMPOSTOS CARBONÍLICOS. SÍNTESE, CARACTERIZAÇÃO E APLICAÇÃO EM CRISTAIS LÍQUIDOS
Condensation reactions of glycerol with aldehydes and ketones were performed under thermal heating and microwave irradiation regimes. Homogeneous and heterogeneous catalysts were tested in both conditions. A silica sulfated (SiO2-SO3H) heterogeneous catalyst demonstrated the best performance relative to a selectivity of >95% in favor of 5-membered ketals. Fo
Quím. Nova. Publicado em: 2015-09
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21. Solventless and Mild Procedure to Prepare Organotellurium(IV) Compounds under Microwave Irradiation
Tellurium(IV) tetrachloride, p-methoxyphenyltellurium trichloride and the corresponding products of its reaction with alkynes were prepared under very mild reaction conditions, in absence of organic solvents and in short reaction times all assisted by microwave irradiation.
J. Braz. Chem. Soc.. Publicado em: 2015-05
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22. Microwave-Assisted Heck Arylations of Non-Activated N-Acyl-3-pyrrolines with Arenediazonium Tetrafluoroborates
Successful Heck-Matsuda arylations of non-activated olefins applying microwave irradiation as an alternative heating mode are presented. Cleaner reactions were performed with arenediazonium tetrafluoroborates bearing electron-donating and electron-withdrawing groups in good to excellent yields with reaction times reduced from 3.5-18 h to 12-30 min.
J. Braz. Chem. Soc.. Publicado em: 2015-05
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23. Rapid Preparation of (BiO)2CO3 Nanosheets by Microwave-Assisted Hydrothermal Method with Promising Photocatalytic Activity Under UV-Vis Light
Crystalline (BiO)2CO3 nanosheets were synthesized by a rapid one-step reaction via microwave-assisted hydrothermal method using urea as a morphology mediator and carbon source. The hydrothermal method combined with microwave heating allowed to obtain sheet-like (BiO)2CO3 particles at shorter reaction times when compared to the conventional heating hydrotherm
J. Braz. Chem. Soc.. Publicado em: 2015-03
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24. MICROWAVE ACTIVATION OF IMMOBILIZED LIPASE FOR TRANSESTERIFICATION OF VEGETABLE OILS
This work investigated the effect of microwave irradiation (MW) on the ethanolysis rate of soybean and sunflower oils catalyzed by supported Novozyme 435 (Candida antarctica). The effects of tert-butanol, water addition and oil:ethanol molar ratio on transesterification were evaluated under conventional heating (CH), and under optimum reaction conditions (wi
Quím. Nova. Publicado em: 2015-03