Use Of Conventional Organic Solvents Research Articles

Deep Eutectic Solvent‐Mediated Oxidative Homocoupling of Terminal Alkynes to 1,3‐Diynes under Mild Green Conditions

AbstractWe prepared a commercially viable Deep Eutectic Solvent (DES) based on Choline Chloride‐Urea‐copper acetate for the first time. It mediates the homocoupling of terminal alkynes, using air as an oxidant. Water is the only by‐product of the entire process. The method avoids ligands, bases, oxidants, and costly palladium catalysts, which qualifies the process greener than ever. The DES can be reused at least three times without affecting the reaction yield significantly. The key features of the protocol that qualify the process as green include the ambient reaction temperatures, lesser use of conventional organic solvents in the reaction, higher yields, and easy product isolation qualify the protocol as a green process.

Modelling and optimization of polyphenol and antioxidant extraction from Rumex hastatus by green glycerol-water solvent according to response surface methodology

Rumex hastatus (RH) is an edible wild herb abundantly distributed in many parts of the world. With the increasing realization of the environmental threats corresponding to the use of conventional organic solvents, the realization to explore efficient green solvents for the extraction of valuable natural products from plants is increasing. The present project, therefore, aimed to discover an optimized efficient and green process for obtaining antioxidant phytochemicals from R. hastatus using aqueous glycerol as a green and low-cost extraction medium. For modelling and optimization according to RSM (response surface methodology), the independent factors were glycerol concentration, temperature and time, and the responses included TPC (total phenolic content), TFC (total flavonoid content), and anti-radical activity (ARA) and iron chelating activity (ICA). The predicted optimum conditions were 52.155% glycerol concentration, 41.303 min extraction time and 50 °C extraction temperature with the predicted values for TPC, TFC, ARA and ICA as 21.65 mg GA/g DW, 95.78 mg RE/g DW, 84.93% and 46.47%, respectively. For responses, well-fitted quadratic models were suggested. Thus, aqueous glycerol is an efficient, green, and cost-effective solvent and its around 50% solution can effectively be used as an extracting medium for antioxidants from R. hastatus. The discovered model should be viable for large scale extraction of bioactive compounds from this plant.

Synthesis of bismuth ferrite by sol-gel auto combustion method: Impact of citric acid concentration on its physicochemical properties

In this study, pure phase BiFeO3 was prepared via a facile sol-gel auto-ignition route using water as a solvent. The influence of citric acid to metal nitrates molar ratio on physicochemical properties of BiFeO3 was also investigated through FTIR, XRD, PL, UV, SEM, and BET analysis. The XRD of the prepared samples revealed the rhombohedral perovskite structures belong to space group R3c. In addition, the BFO2:1 sample showed the smallest crystallite size (42 nm) with the highest purity and recombination rate; while the BFO1:2 sample showed the lowest purity and electron charge recombination rate. The surface areas of the BFO1:1, BFO1:2, and BFO2:1 samples were 1.63, 2.13, and 1.84 m2/g, respectively. Moreover, the bandgaps were found to be 2.17, 2.11, and 2.21 eV for the prepared BFO1:1, BFO1:2, and BFO2:1, respectively. In addition, the appearance of a near-IR band around 814 cm−1 confirms the presence of Bi2Fe4O9 byproduct in the BFO1:2 sample. Finally, SEM revealed that BFO2:1 sample was well-distributed and exhibited uniform morphology, referring to citric acid's ability to stabilize and disperse bismuth ferrite NPs. Furthermore, BFO1:2 sample showed enhanced photocatalytic activity in CR dye degradation than BFO1:1 and BFO2:1 samples, attributed by the increase in the surface area and minimized electron-hole recombination. This strategy eliminates the use of conventional organic solvents and provides an effortless and efficient way to prepare pure BiFeO3 and BiFeO3/Bi2Fe4O9 heterojunction nanocomposite that are potentially applicable for photocatalyst and in solar cell production.

Task‐Specific Deep Eutectic Solvent for Selective Oxidation of Aromatic Methyl to Aldehyde

AbstractBiodegradable and economically viable choline chloride‐FeCl2.H2O deep eutectic solvent (DES), was synthesized and successfully utilized as a catalyst and reaction medium for the selective oxidation of aromatic methyl groups to aldehydes. To demonstrate the synthetic potential of this protocol, the reaction was scaled up to the gram scale. The DES could be reused up to four times without considerable effect on the yield of the reaction. The key features of the protocol that qualify the process as green include the ambient reaction temperatures, easy isolation of the products, higher yields, recyclability of the catalyst, and reactions without the use of conventional organic solvents.

Chemical composition, bioactive compounds extraction, and observed biological activities from jussara (Euterpe edulis): The exotic and endangered Brazilian superfruit.

In this article, we reviewed studies on the fruits of the jussara palm (Euterpe edulis Martius), an endangered Brazilian Atlantic Forest palm tree, also coined as "Superfruit." We summarized the chemical components of the pulp and observed biological activities in murine and humans, as well as the best practices involving the extraction of its target compounds, bioavailability, and stability of extracts. Jussara has shown a rich phenolic profile that justifies its antioxidant properties, in addition to a considerable lipidic and energetic value. As the main feature, the fruit possesses large amounts of anthocyanins that can be commercially explored as a food additive or cosmetic colorants. Recent studies emphasized jussara's antioxidant, anti-inflammatory, and cardioprotective capabilities via reshaping of the gut microbiota. Further knowledge is needed to establish bioavailability and optimal serving size, as many of its antioxidant compounds go under chemical bioconversion in the intestinal tract. While extraction of phenolic compounds, anthocyanins, and oils have interesting results, more studies are required in order to reduce the use of conventional organic solvents and improve their stability and shelf life when added to food products, an area in which nanotechnology seems promising.

De-glycosylation and enhanced bioactivity of flavonoids from apple pomace during extraction with deep eutectic solvents

Extraction and de-glycosylation of glycosylated quercetins in apple pomace was achieved using ‘green’ acidic deep eutectic solvents (DES). The antioxidant activity of the DES extracts was enhanced compared to the use of conventional organic solvents.

Mechanistic Insight into Fast and Highly Efficient Organocatalytic Activity of a Tripodal Dimeric Hexaurea Capsular Assembly in Michael Addition Reactions.

A tris(2-aminoethyl)-amine-based dimeric capsular assembly of pentafluorophenyl urea (C1) has been employed as a catalyst in a wide range of Michael addition reactions. This capsular catalyst assembly dramatically accelerates the Michael addition reaction of β-nitrostyrenes (2a–2d) with various Michael donors such as ketoesters (3a, 3e), 1,3-diketones (3b), diesters (3C), and cyanoesters (3d) at room temperature to yield the corresponding nitroalkanes in significantly high yields within a very short reaction time. Significant improvement in solubility and use of conventional organic solvents in reaction along with a drastic decrease in reaction time (high value of the rate constant of the reaction) has been achieved through C1 as compared to the previously reported homologous tripodal monomeric urea catalyst (L1). The addition of enolate to β-nitrostyrenes to generate an anionic intermediate seemed to be highly stabilized by the six urea units of capsular assembly. Control experiments and in situ kinetic studies are performed for this addition reaction and based on the results, a plausible mechanism has been proposed for the formation of Michael adduct inside the capsular cavity.

Electron beam induced removal of PMMA layer used for graphene transfer

We demonstrate the development of an effective technique to remove the poly methyl methacrylate (PMMA) layer used for transferring graphene synthesized by a chemical vapor deposition (CVD). This was achieved utilizing electron-beam bombardment and following developing processes, prior to the use of conventional organic solvents. Field-effect transistors were fabricated on the transferred graphene in order to explore their Dirac points and carrier motilities in the ambient condition - the results were then compared with those from the conventional wet chemical treatment. It was found that the Dirac points were located close to the zero gate bias when compared to those from the acetone and the acetic acid treatments. Most significantly, the field-effect mobility reached as high as 6770 cm2/Vs and 7350 cm2/Vs on average for holes and electrons, respectively, which is more than seven times improvement in comparison to conventional acetone treatments for CVD-grown graphene devices.

Application of Ionic Liquids in Separation and Downstream Processing of Biomolecules

Use of conventional organic solvents in an extraction brings problems such as toxicity, volatility, flammability and denaturization of biomolecules. In contrast, Ionic liquids, which are called as green solvents, are composed completely of ions and devoid of these problems. Traditional organic solvents have been replaced by Ionic liquids in many industrial applications such as organic synthesis, catalysis, extraction (liquid phase micro-extraction, solid phase micro-extraction and liquid-liquid extraction), adsorption, chromatography (mobile phase additives) and supported liquid membranes. Even though, the applications of ionic liquids in bioseparations are in their early stages, the academic interest in ionic liquids is in the rise. The major applications of ionic liquids in separation technology are presented in this present review paper. Furthermore, the future scenario of the ionic liquids in separation techniques is discussed. Keywords: Ionic liquids, downstream processing, separation, liquid-liquid extraction, supported membranes, extraction.

Sustainable improvement of the tetrabromoethylcyclohexane synthesis using Amino ILs as Catalysts in Water. A facile and environmentally-friendly procedure

BACKGROUND Due to environmental concerns, there is a need to eliminate or drastically reduce the use of conventional organic solvents, as these are environmentally harmful. This paper reports on a novel one-pot synthesis of tetrabromoethylcyclohexane (TBECH) in aqueous medium, using amino-functionalized ionic liquids, which catalyze the reaction and make it more environmentally friendly. RESULTS Compared with the traditional synthesis, tetrabromoethylcyclohexane is obtained with equivalent yield (90%), at room temperature, in a short reaction time (∼2 h compared with the previous 17 h) and with a strong reduction of the use of organic solvents; finally two isomers are obtained instead of four. Furthermore, a novel procedure to prepare the ionic liquids has been designed and two new ones have also been synthesised. The calculated environmental factors (EFs), which measure the environmental sustainability, showed a strong reduction of the use of organic solvents for all syntheses of ionic liquids and TBECHs. CONCLUSIONS The excellent properties of amino-functionalized ionic liquids as solvents and catalysts for chemo- and diastereo-selective bromination of C C bonds in water were confirmed with the synthesis of tetrabromoethylcyclohexane. Given the wide use of brominated compounds in the chemical industry, this procedure could be of wide interest. © 2015 Society of Chemical Industry

Aerobic Oxidation of Benzyl Amines to Benzyl Imines Catalyzed by Metal–Organic Framework Solids

AbstractN‐Hydroxyphthalimide (NHPI) incorporated on a FeIII‐based metal–organic framework [NHPI/Fe(BTC), BTC: 1,3,5‐benzenetricarboxylate)] is used as a heterogeneous catalyst for the aerobic oxidation of benzylamine and its derivatives to their corresponding benzyl imines under neat conditions with molecular oxygen as only oxidant at 100 °C. The catalytic activity of NHPI/Fe(BTC) compares favorably with other heterogeneous catalysts (supported gold nanoparticles) in terms of percentage conversion and selectivity. The reaction appears general in scope and various benzyl amines including heterocyclic amines are also oxidized to the corresponding imines under the present catalytic system. Cross condensation of benzylamine with aniline forms N‐phenylimine in moderate yields. These findings lead to a simple synthetic procedure using commercially available raw materials and eliminate the use of conventional organic solvents.

Application of CO2-expanded solvents in heterogeneous catalysis: a case study

CO2-expanded liquid (CXL) solvents are known to provide optimum reaction and environmental benefits for certain homogeneously catalyzed oxidations. In this work, CXL solvent media are applied to heterogeneously catalyzed oxidations. The oxidation of cyclohexene is investigated as a model reaction. Conversion/selectivity measurements were made in a stirred batch reactor on a MCM-41 encapsulated iron porphyrin chloride complex (p=1–127bar, T=25–50°C, t=4–12h), using either dioxygen or iodosylbenzene as oxidant. Neat acetonitrile and CO2-expanded acetonitrile are used as reaction media. The pressures required for reaction studies in CO2-based media were determined by expansion studies as well as cloud point measurements. For the oxidation with dioxygen, conversion and product yields in CO2-expanded acetonitrile (∼30% CO2) almost doubled compared to the neat organic solvent. In contrast, CO2-replacement of the organic solvent had a negligible effect on conversion and selectivity values when using iodosylbenzene as oxidant. Our results indicate that CXLs significantly reduce the use of conventional organic solvents as reaction media and also enhance catalyst stability against leaching. These advantages suggest that CXLs are promising media for developing green heterogeneous catalytic processes.