Adaptação de forno de microondas doméstico para realização de reações de transesterificação sob refluxo e catálise por argilas

Silva, Fernando de Carvalho da; Ferreira, Vı́tor F.; Souza, Maria Cecília B. V. de

doi:10.1590/s0100-40422006000200032

Cited by 11 publications

(5 citation statements)

References 18 publications

(18 reference statements)

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“…Similar results have been described by adapting domestic ovens to use them as flow systems [13,14]. A recent paper from Leadbeater describes the use of two batch laboratory microwave apparatus, one monomode to perform micro experiments, the other multimode able to irradiate flasks up to 5 L [15].…”

Section: Introductionmentioning

confidence: 58%

“…All batch microwave tests have been conducted with a CEM Explorer PLS, while the flow microwave experiments have been performed with a CEM Voyager [14], both single mode operating systems, working at 2.45 GHz, with a power programmable from 1 to 300 W. Stirring was performed at 400 rpm, with a magnetic nucleus, because the apparatus cannot modulate the speed, not to emulsify and disperse the methanol in oil, but solely to make the mixture temperature homogeneous. Tests were conducted with the ratio methanol/oil of 9/1, 18/1 and 30/1.…”

Section: Apparatusmentioning

confidence: 99%

See 1 more Smart Citation

Biodiesel and FAME synthesis assisted by microwaves: Homogeneous batch and flow processes

Hernando

Letón

Matia

et al. 2007

Fuel

160

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Fatty acids methyl esters (FAME) have been prepared under microwave irradiation, using homogeneous catalysis, either in batch or in a flow system. The quality of the biodiesel obtained has been confirmed by GC analysis of the isolated product. While the initial experiments have been performed in a small scale laboratory batch reactor, the best experiment has been straightforward converted into a stop-flow process, by the use of a microwave flow system. Compared with conventional heating methods, the process using microwaves irradiation proved to be a faster method for alcoholysis of triglycerides with methanol, leading to high yields of FAME.

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Section: Introductionmentioning

confidence: 58%

Section: Apparatusmentioning

confidence: 99%

Biodiesel and FAME synthesis assisted by microwaves: Homogeneous batch and flow processes

Hernando

Letón

Matia

et al. 2007

Fuel

160

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“…17 In addition, our group has investigated new, more efficient and cleaner synthetic methods for the preparation of these mesoionic compounds, 18 especially due to important environmental concerns with the current synthesis. 19,20 Therefore, the synthesis of the 1,3,4-thiadiazolium-2-phenylamine class of compounds was revisited using alternative energy sources to obtain better yields and lower reaction times.…”

Section: Introductionmentioning

confidence: 99%

Improved synthesis of 1,3,4-thiadiazolium-2-phenylamines using microwave and ultrasound irradiation and investigation of their cytotoxic activity

Reis¹,

Echevarria-Lima²,

Miranda³

et al. 2011

J. Braz. Chem. Soc.

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Uma nova e eficiente síntese de oito derivados da classe 1,3,4-tiadiazolio-2-fenilaminas (1-8, sendo o derivado 8 inédito na literatura) foi realizada utilizando cloreto de tionila ou cloreto de trimetilsilano como catalisadores sob irradiação de microondas ou ultra-som. Os compostos alvos foram obtidos em bons rendimentos e em tempo extraordinariamente curtos, 5 min sob irradiação de microondas e 10 min sob irradiação de ultra-som, quando comparados com a metodologia tradicional (24 a 48 h em repouso a temperatura ambiente). Os melhores rendimentos foram obtidos usando irradiação de microondas e, de maneira geral, usando o cloreto de tionila ao invés de cloreto de trimetilsilano. A citotoxicidade foi avaliada frente à linhagem de leucemia humana K562 e do linfoma Daudi, apresentando resultados promissores para o derivado cloreto de 4-fenil-5-(4'-nitro-estiril)-1,3,4-tiadiazolio-2-fenilamina.A new and efficient synthesis of eight 1,3,4-thiadiazolium-2-phenylamine derivatives (1-8, where 8 is novel in the literature) was performed using thionyl chloride or trimethylsilyl chloride as catalysts under microwave or ultrasound irradiation. The target compounds were obtained in good yields and remarkably short times, 5 min under microwave irradiation and 10 min under ultrasound irradiation, where compared to traditional methodology (24 to 48 h at room temperature standing). The best yields were obtained using the microwave irradiation and, in general way, using thionyl chloride instead trimethylsilyl chloride. The cytotoxicity against K562 human leukemia and Daudi lymphoma lines was evaluated and showed promising results from the 4-phenyl-5-(4'-nitro-styryl)-1,3,4-thiadiazolium-2-phenylamine chloride derivative.Keywords: mesoionic heterocycle compounds, microwave, ultrasound, cytotoxic activity IntroductionMesoionic compounds are a special class of heterocycles with potential therapeutic applications due to their unique chemical properties. They possess a betaine-like character with a partial positive charge on the heterocyclic ring that is balanced by a negative charge located on an exocyclic atom or group.1,2 The large separation between the charged regions leads to large dipole moments of about 4-5 D.3,4 These properties suggest the possibility of interacting with biomolecules such as proteins and DNA. Additionally, the overall neutral character of these compounds enables them to cross biological membranes. Different classes of mesoionic compounds have demonstrated a wide range of biological activities such as anti-inflammatory and analgesic, 5 antiparasitic, 6,7 antibacterial, 8,9 antiplatelet, fibrinolytic, thrombolytic and broncholytic effects, 10 as well as anticancer potency.11-17 The promising therapeutic applications have led us to study these interesting compounds in our laboratory. We have previously described the survival enhancement of Ehrlich and Sarcoma 180 tumor-bearing mice treated with 4-phenyl-5-(4'-X-styryl)-1,3,5-thiadiazolium-2-phenylamine chlorides.12 Respiratory chain inhibition, transmembrane ...

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“…Posteriormente, la muestra fue colocada en un horno de microondas durante 60 s, utilizando una potencia de 465 vatios. 28 El horno de microondas utilizado en la síntesis fue un equipo Samsung, modelo MW 1050 de 2,45 GHz.…”

Section: Methodsunclassified

Preparación de nanopartículas de plata en ausencia de polimeros estabilizantes

Sifontes¹,

Melo²,

Maza³

et al. 2010

Quím. Nova

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Recebido em 5/8/09; aceito em 24/2/10; publicado na web em 10/6/10 PREPARATION OF SILVER NANOPARTICLES IN THE ABSENCE OF POLYMER STABILIZERS. Silver nanoparticles (AgNPs) were prepared by means of the polyol method in the absence of stabilizing polymers. To accomplish this objective, AgNO 3 was added to ethylene glycol in the presence of NaOH (1 mol.L -1 ), the suspension formed was irradiated with a microwave source for 60 seconds at a power of 465 watts. It was found that under these conditions AgNPs of sizes between 4-18 nm are formed. Also the results indicate that part of the ethylene glycol is oxidized to carbonyl compounds that reduce the Ag + . These organic compounds are adsorbed on the surfaces of AgNPs, forming a protective film that prevents their aggregation.Keywords: nanoparticles; polyol method; silver. INTRODUCCIÓNRecientemente la preparación de nanopartículas metálicas ha despertado gran interés en la comunidad científica, debido a las propiedades catalíticas, ópticas, electrónicas, magnéticas y bactericidas que presentan estos sistemas, lo que significa que son de gran utilidad tecnológica, siendo de especial atención los materiales que contienen nanopartículas de metales nobles, tales como: oro, 1,2 plata, 3,4 platino 5-7 y paladio. 8Las nanopartículas metálicas se pueden definir como agregados aislados de tamaños entre 1 y 50 nm, los cuales son un conjunto de átomos rodeados de una cápsula protectora o estabilizadora, que evita la aglomeración. 9,10Existen varios métodos para la preparación de nanopartículas; en el caso de los nanoclusters o "nanoagregados" de los metales de transición se pueden citar: 11 reducción química de una sal metá-lica; 12,13 descomposición térmica, fotoquímica o sonoquímica; 14,15 reducción del ligando 11 y desplazamiento del ligando en compuestos organometálicos; deposición del metal en fase de vapor 11 y síntesis electroquímica. 16 Uno de los métodos más comunes para la preparación de las nanopartículas, es la reducción química de sales de metales de transición en presencia de agentes estabilizadores.17,18 El mecanismo de formación de nanopartículas se basa primordialmente, en la reducción de la sal metálica al átomo cerovalente y seguidamente, estos átomos actúan como centros de nucleación dando lugar a la formación de clusters cuyo crecimiento continuará a medida que se sigan agregando los átomos, formándose así, partículas de mayor tamaño y formas poliédricas más complejas.18 No obstante, es necesario estabilizar las partículas mediante la envoltura de moléculas o "agentes" estabilizadores (polí-meros generalmente) que se adsorben en su superficie, inhibiendo de esta manera el proceso de aglomeración o sinterización. 19-22La principal ventaja del método de reducción química es su reproducibilidad y la posibilidad de obtener coloides monodispersos con una distribución estrecha en el tamaño de las partícula, 12 razón por la cual, son frecuentemente preparadas nanopartículas metálicas siguiendo esta metodología, empleando como agentes reductores especies químicas t...

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Adaptação de forno de microondas doméstico para realização de reações de transesterificação sob refluxo e catálise por argilas

Cited by 11 publications

References 18 publications

Biodiesel and FAME synthesis assisted by microwaves: Homogeneous batch and flow processes

Biodiesel and FAME synthesis assisted by microwaves: Homogeneous batch and flow processes

Improved synthesis of 1,3,4-thiadiazolium-2-phenylamines using microwave and ultrasound irradiation and investigation of their cytotoxic activity

Preparación de nanopartículas de plata en ausencia de polimeros estabilizantes

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