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Acidic Ionic Liquids
No full textIonic liquid with acidic properties is an important branch in the wide ionic liquid field and the aim of this article is to cover all aspects of these acidic ionic liquids, especially focusing on the developments in the last four years. The structural diversity and synthesis of acidic ionic liquids are discussed in the introduction sections of this review. In addition, an unambiguous classification system for various types of acidic ionic liquids is presented in the introduction. The physical properties including acidity, thermo-physical properties, ionic conductivity, spectroscopy, and computational studies on acidic ionic liquids are covered in the next sections. The final section provides a comprehensive review on applications of acidic ionic liquids in a wide array of fields including catalysis, CO2 fixation, ionogel, electrolyte, fuel-cell, membrane, biomass processing, biodiesel synthesis, desulfurization of gasoline/diesel, metal processing, and metal electrodeposition
Vanillin based polymers: III. Electrochemical dimerization of vanillin revisited and synthesis of hydrovanilloin–formaldehyde polymer
No full textElectrochemical dimerization of vanillin in basic medium produced mixtures of meso/DL-hydrovanilloins, in contrary to earlier claims of the formation of meso-hydrovanilloin as the sole product. In the reinvestigation we have found that meso-percentage depends on the current density and the highest meso-percentage of 94% is achieved under 64 mA/cm2 current density, using Pb electrodes and 1.25 M aqueous NaOH as the electrolyte. Condensation of the renewable resources based monomer hydrovanilloin with formaldehyde in aqueous NaOH gives hydrovanilloin–formaldehyde polymer in 91% yield. The linear polymer is shown to contain hydrovanilloin units with methylene bridges connecting C-6 positions of the aromatic rings
A Remarkable Oxidative Cascade That Replaces the Riboflavin C8 Methyl with an Amino Group during Roseoflavin Biosynthesis
No full textRoseoflavin is a naturally occurring riboflavin analogue with antibiotic properties. It is biosynthesized from riboflavin in a reaction involving replacement of the C8 methyl with a dimethylamino group. Herein we report the identification of a flavin-dependent enzyme that converts flavin mononucleotide (FMN) and glutamate to 8-amino-FMN via the intermediacy of 8-formyl-FMN. A mechanistic proposal for this remarkable transformation is proposed
From Wires to Cables: Attempted Synthesis of 1,3,5-Trifluorenylcyclohexane as a Platform for Molecular Cables
No full textMultiple molecular wires braided together in a single assembly, termed as molecular cable, are promising next-generation materials for effective long-range charge transport. As an example of the platform for constructing molecular cables, 1,3,5-trifluorenylcyclohexane (TFC) and its difluorenyl analogues (DFCs) were systematically investigated both experimentally (X-ray crystallography) and theoretically (DFT calculations). Although the syntheses of DFCs were successfully achieved, the synthesis of TFC, which involved a similar intramolecular Friedel-Crafts cyclization as the last step, was unsuccessful. An exhaustive study of the conformational landscape of cyclohexane ring of TFC and DFCs revealed that TFC is a moderately strained molecule (∼17 kcal/mol), and computational studies of the reaction profile show that this steric strain, present in the transition state, is responsible for the unusually high (∼5 years) reaction half-life. A successful synthesis of TFC will require that the steric strain is introduced in multiple steps, and such alternative strategies are being currently explored. (Chemical Equation Presented)
Domestic environmental policy and international cooperation for global commons
No full textThe paper analyzes the strategic behavior of several countries engaged in capital accumulation, pollution mitigation, and environmental adaptation in the context of an environmental common good. Both cooperative and non-cooperative strategies are discussed. The non-cooperative strategy is a dynamic game in which each country makes its own environmental decision following the open-loop Nash equilibrium. The cooperative social planner problem assumes an international environmental agreement in force. The non-cooperative and cooperative solutions are compared in the symmetric case of two countries and extended to several identical countries. It is shown that the non-cooperative strategy in multi-country world leads to over-production, over-consumption, over-pollution, and over-adaptation
The TRI-AG Academics Research Extension College Of Agriculture Sciences - Vol.1 Vol.5 - 2015
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Non-canonical active site architecture of the radical SAM thiamin pyrimidine synthase
No full textRadical S-adenosylmethionine (SAM) enzymes use a [4Fe-4S] cluster to generate a 5′-deoxyadenosyl radical. Canonical radical SAM enzymes are characterized by a β-barrel-like fold and SAM anchors to the differentiated iron of the cluster, which is located near the amino terminus and within the β-barrel, through its amino and carboxylate groups. Here we show that ThiC, the thiamin pyrimidine synthase in plants and bacteria, contains a tethered cluster-binding domain at its carboxy terminus that moves in and out of the active site during catalysis. In contrast to canonical radical SAM enzymes, we predict that SAM anchors to an additional active site metal through its amino and carboxylate groups. Superimposition of the catalytic domains of ThiC and glutamate mutase shows that these two enzymes share similar active site architectures, thus providing strong evidence for an evolutionary link between the radical SAM and adenosylcobalamin-dependent enzyme superfamilies
NaOH catalyzed condensation reactions between levulinic acid and biomass derived furan-aldehydes in water
No full textNaOH catalyzed condensation reaction between 5-hydroxymethylfurfural and levulinic acid in water gives a 2.5: 1 mixture of aldol products: (E)-6-[5-(hydroxymethyl)furan-2-yl]-hex-4-oxo-5-enoic acid and (E)-3-[5-(hydroxymethyl)furan-2-yl]methylene-4-oxo-pentanoic acid in 82% combined yield. A similar reaction between furfural and levulinic acid gives the linear polymer, poly[1-carboxymethyl-4-(furan-2-yl)-2-oxo-butane-1,4-diyl] in 91% yield