1,721,124 research outputs found
Carbonate based ionic liquids and beyond
Full text linkIonic liquids appear almost like a different state of matter. Just like mercury, that I enjoyed playing with as a child after bursting thermometers. A liquid metal, and a liquid salt at room temperature are awe-inspiring, as their physical state is counterintuitive. We struggle to accept that a metal may not be hard, and that a salt may be non-crystalline, let alone liquid.
Thus, for sheer curiosity, we started synthesising ammonium and phosphonium ionic liquids. The first hurdle was to make them efficiently, colourless and pure. And this was achieved by using dimethylcarbonate (non-toxic) instead of alkyl halides as quaternarisation reagent. These syntheses were, efficient (100% atom economic), tuneable, halide-free, and produced only CO2 and methanol as by-products.1
But, ionic liquids are not just pretty. So what can we do with them?
Use them as green solvents? Sometimes yes, but often too costly, and not always an elegant or green application.
Unless we can design multiphase solvent systems with other advantages.2-3
It’s might also interesting to take advantage of the chemical properties of their ions,4 or to use them as catalysts,5-6 including for the upgrade of biogenic chemicals.7
The next question might be on how these materials work, e.g. as catalysts,8 and how can these properties be monitored.9 Or whether they can be used to make new devices, e.g. based on their luminescence.10
And why not try to make old compounds, e.g. choline, by these methods?
We will discuss this “genealogy” of applications and of examples, applied to a family of carbonate based ionic liquids.
1. Fabris, M.; Lucchini, V.; Noè, M.; Perosa, A.; Selva, M., Chem. Eur. J. 2009, 15 (45), 12273-12282.
2. Tundo, P.; Perosa, A., Chem. Soc. Rev. 2007, 36 (3), 532-550.
3. Gottardo`, M.`; Selva`, M.`; Perosa`, A. work in progress
4. Noè, M.; Perosa, A.; Selva, M.; Zambelli, L., Green Chem. 2010, 12 (9), 1654-1660.
5. Fabris, M.; Noe, M.; Perosa, A.; Selva, M.; Ballini, R., J. Org. Chem. 2012, 77 (4), 1805-1811.
6. Selva, M.; Noe, M.; Perosa, A.; Gottardo, M., Org. Biomol. Chem. 2012, 10 (32), 6569-6578.
7. Stanley`, J.`; Caretto`, A.`; Perosa`, A. work in progress
8. Lucchini, V.; Noè, M.; Selva, M.; Fabris, M.; Perosa, A., Chem. Commun. 2012, 48 (42), 5178-5180.
9. Lucchini, V.; Fabris, M.; Noe, M.; Perosa, A.; Selva, M., Int. J. Chem. Kinet. 2011, 43 (3), 154-160.
10. Fiorani`, G.; Selva, M.; Perosa`, A.`; Malba, C.; work in progress
Systems Thinking: Adopting an Emergy Perspective as a Tool for Teaching Green Chemistry
No full textGreen chemistry is the name of a need, that of encompassing chemistry research and the environmental, safety, health, and societal issues that have been creating unprecedent concerns at a global level. Green chemistry is a modern concept, as the label that represents the entry of chemical sciences in the realm of integrated sustainability studies. To do green chemistry research, we need approaches that take into account the use and availability of resources, as well as the direct or indirect impacts of the applications of new chemistry. Systems thinking is a powerful mindset for addressing the complexity of the interconnections between the traditional and the new aspects of chemistry research. Systems thinking can provide suitable and appropriate conceptual tools for the research, requiring that chemistry teaching provides the necessary familiarity with systemic concepts and practices. In this paper, an emergy (spelled with “m”) perspective is presented as suitable to address the green chemistry didactics toward a systemic conceptual framework, which is now more and more mandatory
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Diethylene Glycol/NaBr Catalyzed CO2 Insertion into Terminal Epoxides: From Batch to Continuous Flow
Full text linkCO2 insertion reactions on terminal epoxides (styrene oxide, 1,2-epoxyhexane and butyl glycidyl ether) were performed in a binary homogeneous mixture comprising NaBr as the nucleophilic catalyst and diethylene glycol (DEG) as both solvent and catalyst activator (cation coordinating agent). The reaction protocol was initially studied under batch conditions either in autoclaves and glass reactors: quantitative formation of the cyclic organic carbonate products (COCs) were achieved at T=100 °C and p0(CO2)=1–40 bar. The process was then transferred to continuous-flow (CF) mode. The effects of the reaction parameters (T, p(CO2), catalyst loading, and flow rates) were studied using microfluidic reactors of capacities variable from 7.85 ⋅ 10−2 to 0.157 cm3. Albeit the CF reaction took place at T=220 °C and 120 bar, CF improved the productivity and allowed catalyst recycle through a semi-continuous extraction procedure. For the model case of 1,2-epoxyhexane, the (non-optimized) rate of formation of the corresponding carbonate, 4-butyl-1,3-dioxolan-2-one, was increased up to 27.6 mmol h−1 equiv.−1, a value 2.5 higher than in the batch mode. Moreover, the NaBr/DEG mixture was reusable without loss of performance for at least 4 subsequent CF-tests
Fish-Waste-Derived Gelatin and Carbon Dots for Biobased UV-Blocking Films
Full text linkThe fish industry produces every year huge amounts of waste that represent an underutilized source of chemical richness. In this contribution, type I collagen was extracted from the scales of Mugil cephalus and carbon dots (CDs) were synthesized from the scales of Dicentrarchus labrax. These materials were combined to make hybrid films with UV-blocking ability, by casting a mixture of gelatin, glycerol (15%), and CDs (0, 1, 3, and 5%). The films were fully characterized from the mechanical, morphological, and optical point of view. Here, 40 μm thick films were obtained, characterized by a high water solubility (70%); moreover, the presence of CDs improved the film mechanical properties, in particular increasing the tensile strength (TS) up to 17 MPa and elongation at break (EAB) up to 40%. The CDs also modulated water vapor permeability and the thermal stability of the films. From the optical point of view, with just 5% loading of CDs the films blocked almost 70% of the UV radiation with negligible change in transparency (88.6% for the nonloaded vs 84.4% for 5% CDs) and opacity (1.32 for nonloaded vs 1.61 for 5% CDs). These types of hybrid biobased films hold promise for the production of sustainable UV-shields both for human health and for prolonging the shelf life of food
RETINOL-BINDING PROTEIN E PREALBUMINA: NUOVI INDICI DI FUNZIONALITA' EPATOCITARIA IN CHIRURGIA DIGESTIVA
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Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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