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Microwave-Assisted Ionic Liquid-Catalyzed Selective Monoesterification of Alkylphosphonic Acids-An Experimental and a Theoretical Study.

ABSTRACT: It is well-known that the P-acids including phosphonic acids resist undergoing direct esterification. However, it was found that a series of alkylphoshonic acids could be involved in monoesterification with C₂-C₄ alcohols under microwave (MW) irradiation in the presence of [bmim][BF₄] as an additive. The selectivity amounted to 80-98%, while the isolated yields fell in the range of 61-79%. The method developed is a green method for P-acid esterification. DFT calculations at the M062X/6-311+G (d,p) level of theory (performed considering the solvent effect of the corresponding alcohol) explored the three-step mechanism, and justified a higher enthalpy of activation (160.6-194.1 kJ·mol^-1) that may be overcome only by MW irradiation. The major role of the [bmim][BF₄] additive is to increase the absorption of MW energy. The specific chemical role of the [BF₄] anion of the ionic liquid in an alternative mechanism was also raised by the computations.

SUBMITTER: Harsagi N

PROVIDER: S-EPMC8434145 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Ultrasonication-Assisted and Benzimidazolium-Based Bronsted Acid Ionic Liquid-Catalyzed Transesterification of Castor Oil.

Project description:In this investigation, we report the synthesis of biodiesel using benzimidazolium-based brønsted acid ionic liquid (BBAIL) catalyst under the influence of ultrasonication. The prepared BBAIL catalyst was characterized by Fourier transform infrared and NMR spectroscopy techniques, and its acidity was determined by the Hammett method with 4-nitroaniline as the indicator. Ultrasonicator horn (22 kHz, 500 W) was used in this work with an on-off cycle of 50-20 s at 70% amplitude. The highest biodiesel yield of 96% was achieved by ultrasonication when 1:10 molar ratio of castor oil to methyl alcohol was used at 50 °C temperature with 9 mol % of the catalyst in just 90 min, which is about 10 times lesser than the process without ultrasonication. At similar conditions, 96% biodiesel yield was obtained in 14 h without ultrasonication. In summary, ultrasonication proved to be an efficient way to improve biodiesel synthesis in less time and BBAIL showed excellent activity toward the conversion of glycerides to synthesize biodiesel. Other important highlights are easy separation of the catalyst and recyclability up to three cycles with small decrease in its activity.

| S-EPMC6643412 | biostudies-literature

Theoretical and Experimental Study of Light-assisted Polymerization by Multimechanism Action.

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| S-EPMC5153847 | biostudies-other

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| S-EPMC8510021 | biostudies-literature

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| S-EPMC6215560 | biostudies-literature

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| S-EPMC3875327 | biostudies-literature

Hydroxyl Functionalized Pyridinium Ionic Liquids: Experimental and Theoretical Study on Physicochemical and Electrochemical Properties.

Project description:Structurally modified hydroxyl functionalized pyridinium ionic liquids (ILs), liquid at room temperature, were synthesized and characterized. Alkylated N-(2-hydroxyethyl)-pyridinium ILs were prepared from alkylpyridines via corresponding bromide salts by N-alkylation (65-93%) and final anion exchange (75-96%). Pyridinium-alkylation strongly influenced the IL physicochemical and electrochemical properties. Experimental values for the ILs physicochemical properties (density, viscosity, conductivity, and thermal decomposition temperature), were in good agreement with corresponding predicted values obtained by theoretical calculations. The pyridinium ILs have electrochemical window of 3.0-5.4 V and were thermally stable up to 405°C. The IL viscosity and density were measured over a wide temperature range (25-80°C). Pyridine alkyl-substitution strongly affected the partial positive charge on the nitrogen atom of the pyridinium cations, as shown by charge distribution calculations. On-going studies on Mg complexes of the new ILs demonstrate promising properties for high current density electrodeposition of magnesium.

| S-EPMC6759651 | biostudies-literature

Combined Experimental and Theoretical Study of the Competitive Absorption of CO<sub>2</sub> and NO<sub>2</sub> by a Superbase Ionic Liquid.

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| S-EPMC8296676 | biostudies-literature

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| S-EPMC4641455 | biostudies-literature

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Project description:The decomposition of S-nitrosothiols (RSNO) in solution under oxidative conditions is significantly faster than can be accounted for by homolysis of the S-N bond. Here we propose a cationic chain mechanism in which nitrosation of nitrosothiol produces a nitrosated cation that, in turn, reacts with a second nitrosothiol to produce nitrosated disulfide and the NO dimer. The nitrosated disulfide acts as a source of nitrosonium for nitrosothiol nitrosation, completing the catalytic cycle. The mechanism accounts for several unexplained facets of nitrosothiol chemistry in solution, including the observation that the decomposition of an RSNO is accelerated by O(2), mixtures of O(2) and NO, and other oxidants, that decomposition is inhibited by thiols and other antioxidants, that decomposition is dependent on sulfur substitution, and that decomposition often shows nonintegral kinetic orders.

| S-EPMC2519156 | biostudies-literature

A combined experimental and theoretical study of ion solvation in liquid N-methylacetamide.

Project description:Most current biomolecular simulations are based on potential energy functions that treat the electrostatic energy as a sum of pairwise Coulombic interactions between effective fixed atomic charges. This approximation, in which many-body induced polarization effects are included in an average way, is expected to be satisfactory for a wide range of systems, but less accurate for processes involving the transfer and partition of ions among heterogeneous environments. The limitations of these potential energy functions are perhaps most obvious in studies of ion permeation through membrane channels. In many cases, the pore is so narrow that the permeating ion must shed most of its surrounding water molecules and the large energetic loss due to dehydration must be compensated by coordination with protein atoms. Interactions of cations with protein backbone carbonyl oxygens, in particular, play a critical role in several important biological channels. As a first step toward meeting the challenge of developing an accurate explicit accounting for induced polarization effects, the present work combines experiments and computation to characterize the interactions of alkali and halide ions with N-methylacetamide chosen to represent the peptide bond. From solubility measurements, we extract the solvation free energies of KCl and NaCl in liquid N-methylacetamide. Polarizable models based on the Drude oscillator are then developed and compared with available experimental and ab initio data. The good agreement for a range of structural and thermodynamic properties in the gas and condensed phases suggests that the polarizable models provide an accurate representation of ion-amide interactions in biological systems.

| S-EPMC3109503 | biostudies-literature

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