A Study of the Ionic Liquid Mediated Microwave Heating of Organic Solvents
TL;DR: It is shown that hexane and toluene together with solvents such as THF and dioxane can be heated way above their boiling point in sealed vessels using a small quantity of an ionic liquid, thereby allowing them to be used as media for microwave-assisted chemistry.
Abstract: The use of ionic liquids as aids for microwave heating of nonpolar solvents has been investigated. We show that hexane and toluene together with solvents such as THF and dioxane can be heated way above their boiling point in sealed vessels using a small quantity of an ionic liquid, thereby allowing them to be used as media for microwave-assisted chemistry. Using the appropriate ionic liquid, the heating can be performed with no contamination of the solvent. To show the applicability of the system, two test reactions have been successfully performed.
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TL;DR: This Review highlights recent applications of controlled microwave heating in modern organic synthesis, and discusses some of the underlying phenomena and issues involved.
Abstract: Although fire is now rarely used in synthetic chemistry, it was not until Robert Bunsen invented the burner in 1855 that the energy from this heat source could be applied to a reaction vessel in a focused manner. The Bunsen burner was later superseded by the isomantle, oil bath, or hot plate as a source for applying heat to a chemical reaction. In the past few years, heating and driving chemical reactions by microwave energy has been an increasingly popular theme in the scientific community. This nonclassical heating technique is slowly moving from a laboratory curiosity to an established technique that is heavily used in both academia and industry. The efficiency of "microwave flash heating" in dramatically reducing reaction times (from days and hours to minutes and seconds) is just one of the many advantages. This Review highlights recent applications of controlled microwave heating in modern organic synthesis, and discusses some of the underlying phenomena and issues involved.
3,044 citations
TL;DR: An overview of the thermal effects and the current state of non-thermal microwave effects is presented in this critical review along with a view on how these phenomena can be effectively used in organic synthesis.
Abstract: Microwave irradiation has been successfully applied in organic chemistry. Spectacular accelerations, higher yields under milder reaction conditions and higher product purities have all been reported. Indeed, a number of authors have described success in reactions that do not occur by conventional heating and even modifications of selectivity (chemo-, regio- and stereoselectivity). The effect of microwave irradiation in organic synthesis is a combination of thermal effects, arising from the heating rate, superheating or “hot spots” and the selective absorption of radiation by polar substances. Such phenomena are not usually accessible by classical heating and the existence of non-thermal effects of highly polarizing radiation—the “specific microwave effect”—is still a controversial topic. An overview of the thermal effects and the current state of non-thermal microwave effects is presented in this critical review along with a view on how these phenomena can be effectively used in organic synthesis.
1,603 citations
TL;DR: A linear free energy approach is used to characterize 17 RTILs on the basis of their distinct multiple solvation interactions with probe solute molecules and provides data that can be used to help identify the interactions and properties that are important for specific chemical applications.
Abstract: Room-temperature ionic liquids (RTILs) are useful in many chemical applications. Recent publications have attempted to determine the polarity of RTILs using empirical solvent polarity scales. The results have indicated that most RTILs have similar polarities. Nevertheless, RTILs are capable of behaving quite differently when used as solvents in organic synthesis, matrixes in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, liquid−liquid extraction, and as stationary phases in gas chromatography. The work presented in this study uses a linear free energy approach to characterize 17 RTILs on the basis of their distinct multiple solvation interactions with probe solute molecules. This model provides data that can be used to help identify the interactions and properties that are important for specific chemical applications.
1,028 citations
TL;DR: In this article, the authors focus on the use of nano-catalysis for green chemistry development including the strategy of using microwave heating with nanocatalysis in benign aqueous reaction media which offers an extraordinary synergistic effect with greater potential than these three components in isolation.
1,005 citations
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TL;DR: The partitioning of simple substituted-benzene derivatives between water and the room temperature ionic liquid, butylmethylimidazolium hexafluorophosphate, is based on the solutes' charged state or relative hydrophobicity as discussed by the authors.
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TL;DR: In this paper, four different types of organic reactions have been studied and seven different organic compounds have been prepared, under pressure in a microwave oven, and considerable rate increases have been observed.
1,509 citations
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