scholarly journals Utilization of Dissociation Constant (pKa) Value Perspective of -CH Acid in Electrochemical Synthesis of 4H-Chromene and its Derivatives

2020 ◽  
Vol 32 (7) ◽  
pp. 1697-1702
Author(s):  
Apoorv Saraswat ◽  
Rana Krishna Pal Singh
Keyword(s):  
Dissociation Constant ◽  
Electrochemical Synthesis ◽  
Acidic Property ◽  
Covalently Bonded ◽  
Pka Value ◽  
Platinum Cathode ◽  
Controlled Potential ◽  
Work Up ◽  
Reaction Media

Activation of acidic-H in C-H chemistry through imposition of proper electrode potential is a matter of concern among synthetic research community. In this study, our main aim is to get deeper insight into the dissociation constant (pKa) value perspective of -CH acid and its utilization in electro-catalytic transformation. Herein, a platinum cathode was being used to attract a covalently bonded electrons that exist between C and active-H of CH-acid (dimedone) toward itself i.e. cathodic part to form acidic-H and thus, form in-situ tautomeric enol form that acts as electro-generated base. Utilization of this notability has been accomplished by electrochemical synthesis of 4H-chromene and its derivatives by performing cathodic reduction. Due to acidic property of dimedone, cathodic platinum electrode draw the potential switched to lower side that is being recorded through the potential-cum-galvanostat which facilitates the faster transfer of electrons from -CH acid to form enolate ion of dimedone that act as electro-generated base for the reaction media which simultaneously undergoes cascade reaction (Michael addition/cyclization) on activated alkene (α-cyanocinnamonitrile derivatives). This approach offers several advantages such as good yield, mild reaction condition, easy accessible, simple work-up procedure and controlled potential selectivity at cathode. Use of no base is pivotal section of this methodology. Electro-generated base is used instead of chemical toxic bases, so the present protocol is green as electrons that acts as intrinsically sole reagent for the reaction media which is renewable, hence sustainable for the safe future.

scholarly journals In-situ Electrochemical Synthesis of Core-shell Structural NbC@Nb5Si3/Nb Composites in Molten Salt

2021 ◽  
Vol 714 (3) ◽  
pp. 032008
Author(s):  
Hongmei Li ◽  
Zhisheng Nong ◽  
Qian Xu ◽  
Qiushi Song ◽  
Ying Chen ◽  
...  
Keyword(s):  
Molten Salt ◽  
Electrochemical Synthesis ◽  
Core Shell

scholarly journals Dealloying progress during nanoporous structure evolution analyzed by in situ resistometry

2017 ◽  
Vol 19 (44) ◽  
pp. 29880-29885 ◽  
Author(s):  
Eva-Maria Steyskal ◽  
Michael Seidl ◽  
Matthias Graf ◽  
Roland Würschum
Keyword(s):  
Electrochemical Synthesis ◽  
Synthesis Method ◽  
Nanoporous Structure ◽  
Structure Evolution ◽  
Nanoporous Structures

The progress of dealloying, an electrochemical synthesis method capable of producing nanoporous structures with bulk outer dimensions, is studied by in situ resistometry.

scholarly journals Computer programs for calculating pKa: A comparative study for 3-[3-(2-nitrophenyl)prop-2-enoyl]-2h-1-benzopyran-2-one

2010 ◽  
Vol 75 (2) ◽  
pp. 243-248 ◽  
Author(s):  
Selma Spirtovic-Halilovic ◽  
Davorka Zavrsnik
Keyword(s):  
Antimicrobial Activity ◽  
Computer Program ◽  
Dissociation Constant ◽  
Chemical Compounds ◽  
Computer Programs ◽  
Good Activity ◽  
Target Compound ◽  
Theoretical Approaches ◽  
Pka Value ◽  
Good Agreement

Coumarin-based compounds containing a chalcone moiety exhibit antimicrobial activity. These substances are potential drugs and it is important to determine their pKa values. However, they are almost insoluble in water. The dissociation constant was experimentally determined by potentiometric titration for 3-[3-(2-nitrophenyl)prop-2-enoyl]-2H-1-benzopyran-2-one because this compound shows good activity and solubility. A number of different computer programs for the calculation of the dissociation constant of chemical compounds have been developed. The pKa value of the target compound was calculated using three different computer programs, i.e., the ACD/pKa, CSpKaPredictor and ADME/ToxWEB programs, which are based on different theoretical approaches. The analysis demonstrated good agreement between the experimentally observed pKa value of 3-[3-(2-nitrophenyl)prop-2-enoyl]-2H-1-benzopyran- 2-one and the value calculated using the computer program CSpKa.

scholarly journals Direct Electrochemical Synthesis of Bismuth(III) Phenoxides and their Coordination Compounds

2012 ◽  
Vol 9 (1) ◽  
pp. 381-388 ◽  
Author(s):  
Harpreet Kaur ◽  
Baljit Singh
Keyword(s):  
Elemental Analysis ◽  
Electrochemical Synthesis ◽  
Coordination Compounds ◽  
Supporting Electrolyte ◽  
Spectral Studies ◽  
Electrochemical Reactions ◽  
Hydroxybenzoic Acid ◽  
Platinum Cathode ◽  
Infrared Spectral ◽  
Tetrabutylammonium Chloride

Bismuth(III) phenoxides have been synthesized by electrochemical reactions of 1-naphthol, 2-naphthol, 4-aminophenol, 2-nitrophenol, 4-nitrophenol, 2-hydroxybenzoic acid,p-cresol, phenol, resorcinol, 2-tert-butylphenol and 2-tert-butyl-4-methoxyphenol at sacrificial bismuth anode and inert platinum cathode using tetrabutylammonium chloride as supporting electrolyte. The coordination compounds of these phenols with 1, 10-phenanthroline and 2, 2ʼ-bipyridyl have also been synthesized electrochemically. The solid products separated in the anode compartment have been isolated and characterized by elemental analysis and infrared spectral studies. Current efficiencies of these reactions are quite high.

Synthesis of 1,8-dioxo-octahydro-xanthene and tetrahydrobenzo[b]pyran derivatives promoted by two bis-imidazolium-based ionic liquids

2021 ◽  
Vol 08 ◽  
Author(s):  
Maryam Shirzad ◽  
Mitra Nasiri ◽  
Nader Daneshvar ◽  
Farhad Shirini ◽  
Hassan Tajik
Keyword(s):  
Ionic Liquid ◽  
Ionic Liquids ◽  
Knoevenagel Condensation ◽  
Reaction Rates ◽  
Xanthene Derivatives ◽  
Acidic Ionic Liquids ◽  
Dicationic Ionic Liquids ◽  
Acidic Nature ◽  
Work Up ◽  
Reaction Media

Aim and objective: In this work, we have prepared two bis-dicationic ionic liquids with the same cationic core (Bis-imidazole) and different counter-anions using sulfuric acid and perchloric acids. After that, the efficiency and ability of these compounds as catalysts were investigated and compared in the promotion of Knoevenagel condensation and synthesis of benzo[b]pyran derivatives to see the effect of the anionic counter-part in the reaction. Material and method: In a 25 mL round-bottomed flask, a mixture of aldehyde (1.0 mmol), 1,3-cyclodicarbonyl (2.0 mmol) and the desired amount of the mentioned acidic ionic liquids was heated at 90°C in the absence of solvent (Reaction A) or In a 25 mL round-bottomed flask, a mixture of aldehyde (1.0 mmol), 1,3-cyclodicarbonyl (1.0 mmol), malononitrile, (1.1 mmol) and optimized amounts of the ionic liquid in water (3.0 mL) was heated at 80°C (Reaction B) for the appropriated time. After the completion of the reactions which were monitored by TLC (n-hexane: EtOAc; 3:1), 10 mL of water was added and the mixture was stirred for 2 minutes. Then, the products were separated by filtration and were washed several times with water. After drying, the pure products were obtained while there was no need to further. Results: Comparison of the obtained results from both of the ionic liquids revealed that [H2-Bisim][HSO4]2 because of its more acidic structure had a more catalytic activity for the preparation of 1,8-dioxo-octahydro-xanthene derivatives but [H2-Bisim][ClO4]2 was relatively more efficient for the synthesis of tetrahydrobenzo[b]pyran derivatives since the stronger acidic nature of [H2-Bisim][HSO4]2 may prevent the simple activation of malononitrile in the reaction media. Conclusion: In this study, we have introduced efficient methods for the synthesis of 1,8-dioxo-octahydro-xanthene and tetrahydrobenzo[b]pyran derivatives in the presence of catalytic amounts of [H2-Bisim][ClO4]2 and [H2-Bisim][HSO4]2 These methods have several advantages such as ease of preparation and handling of the catalysts, high reaction rates, excellent yields, eco-friendly procedures and simple work-up.

scholarly journals Modification of Poly(4-methyl-2-pentyne) in the Supercritical Fluid Medium for Selective Membrane Separation of CO2 from Various Gas Mixtures

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2468
Author(s):  
Viktoriya Polevaya ◽  
Anton Vorobei ◽  
Andrey Gavrikov ◽  
Samira Matson ◽  
Olga Parenago ◽  
...  
Keyword(s):  
Membrane Separation ◽  
Gas Permeability ◽  
Gas Mixtures ◽  
Fluid Medium ◽  
Selective Membrane ◽  
Separation Of Co2 ◽  
Reaction Media ◽  
First Time ◽  
Principal Possibility

The modification of highly permeable films of brominated 1,2-disubstituted polyacetylene, poly(4-methyl-2-penthyne), via incorporation of in situ formed butylimidazolium bromide is reported for the first time. Principal possibility and efficiency of supercritical CO2 and CHF3 use as reaction media for the corresponding process, namely for quaternization of butylimidazole by brominated polymer are revealed. As a result, we prepared new membrane materials possessing promising properties such as stability toward organic solvents, good mechanical properties and significantly improved CO2-selectivity while maintaining gas permeability at high values. Comparative analysis of the results allowed us to determine content and conditions for the incorporation of butylimidazolium groups optimal for most efficient separation of CO2 from industrial gas mixtures. These results are of interest for the designing of new CO2 selective membranes.

Sign in / Sign up

Export Citation Format

Share Document