Microwave-Assisted Chemistry – A Stock Taking

In 1986 Gedye and Giguere published the first important articles on the influence of microwaves (2.45 GHz) on syntheses undertaken in household ovens. Over the past 20 years there have been various developments in different directions reflecting a steadily growing interest in this innovative field. This mini-overview focuses on selected details of reaction engineering in microwave chemistry

Microwave-Assisted Extraction – A State-of-the-Art Overview of Varieties

The microwave-assisted extraction technique offers some advantages over conventional extraction methods. Applications include the extraction of high-value compounds from natural sources including nutraceutical and functional food ingredients, pharma actives from biomass, and phytonutrients. Compared to conventional solvent extraction methods, the microwave-assisted extraction (MAE) technique offers advantages such as improved stability of products and marker compounds, increased purity of crude extracts, the possibility to use less toxic solvents, reduced processing costs, reduced energy and solvent consumption, increased recovery and purity of marker compounds, and very rapid extraction rates

Biomass-Derived Platform Chemicals: Thermodynamic Studies on the Extraction of 5‑Hydroxymethylfurfural from Ionic Liquids

Activity coefficients at infinite dilution, γ_<i>i</i>^∞, of 13 solutes such as alkanes, alkenes, alkylbenzenes, alcohols, esters, and ethers in six 1,3-dialkylimidazolium- or tetraalkylphosphonium-based ionic liquids have been determined by gas chromatography using the ionic liquids as the stationary phase. Furthermore, the solubility of 5-hydroxymethylfurfural (HMF) in these solutes and the solubility of the solutes in 1-butyl-3-methylimidazolium methanesulfonate ([C₄mim]­[CH₃SO₃]) was assessed. The combination of these data allowed for the interpretation of prevailing interactions on molecular level and resulted in the hypothesis that an ideal extracting agent must feature hydrogen bond acceptor properties to obtain high extraction efficiencies of hydrogen bond donor molecules such as HMF from this ionic liquid. Extraction data obtained using the thus proposed extracting agents demonstrated that this hypothesis was correct and can in future be transposed to other separation problems. In the case of a multifunctional molecule such as HMF, extraction efficiencies are however in general low and can only be little improved by removing other potential interaction sites from the ionic liquid’s cation: hence, in the <i>N</i>-ethyl-<i>N</i>-methylpyrrolidinium analogue [C₂C₁pyr]­[CH₃SO₃], π–π-interactions between cation and HMF cannot form, which increases the extraction efficiency somewhat