http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Significant Improvement of Catalytic Efficiencies in Ionic Liquids
송충의,최두성,Mi Young Yoon 대한화학회 2005 Bulletin of the Korean Chemical Society Vol.26 No.9
The use of ionic liquids as reaction media can confer many advantages upon catalytic reactions over reactions in organic solvents. In ionic liquids, catalysts having polar or ionic character can easily be immobilized without additional structural modification and thus the ionic solutions containing the catalyst can easily be separated from the reagents and reaction products, and then, be reused. More interestingly, switching from an organic solvent to an ionic liquid often results in a significant improvement in catalytic performance (e.g., rate acceleration, (enantio)selectivity improvement and an increase in catalyst stability). In this review, some recent interesting results which can nicely demonstrate these positive “ionic liquid effect” on catalysis are discussed.
Cinchona-based Sulfonamide Organocatalysts: Concept, Scope, and Practical Applications
배한용,송충의 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.6
Cinchona-based bifunctional catalysts have been extensively employed in the field of organocatalysis due to the incorporation of both hydrogen-bonding acceptors (quinuclidine) and hydrogen-bonding donors (e.g., alcohol, amide, (thio)urea and squaramide) in the molecule, which can simultaneously activate nucleophiles and electrophiles, respectively. Among them, cinchona-derived (thio)urea and squaramide catalysts have shown remarkable application potential by using their bifurcated hydrogen bonding donors in activating electrophilic carbonyls and imines. However, due to their bifunctional nature, they tend to aggregate via interand intramolecular acid-base interactions under certain conditions, which can lead to a decrease in the enantioselectivity of the reaction. To overcome this self-aggregation problem of bifunctional organocatalysts, we have successfully developed a series of sulfonamide-based organocatalysts, which do not aggregate under conventional reaction conditions. Herein, we summarize the recent applications of our cinchona-derived sulfonamide organocatalysts in highly enantioselective methanolytic desymmetrization and decarboxylative aldol reactions. Immobilization of sulfonamide-based catalysts onto solid supports allowed for unprecedented practical applications in the synthesis of valuable bioactive synthons with excellent enantioselectivities.
Organic radical battery with PTMA cathode: Effect of PTMA content on electrochemical properties
김재광,송충의,Gouri Cheruvally,서양곤,최두성,Seo-Hwan Lee,안주현 한국공업화학회 2008 Journal of Industrial and Engineering Chemistry Vol.14 No.3
The nitroxide radical polymer, poly(2,2,6,6-tetramethylpiperidinyloxy-4-ylmethacrylate) (PTMA) is gaining increasing attention as a promising cathode-active material for high-rate capable, organic radical batteries (ORBs). This study evaluates the effect of varying PTMA content (20, 40 and 60wt.%) on the cathode morphology and electrochemical properties of the ORB operating at room temperature with lithium metal anode and 1M LiPF6 in ethylene carbonate (EC)/dimethyl carbonate (DMC) electrolyte. The cathodes with 20 and 40% of PTMA exhibited uniform particle morphology with a thin layer of polymer coating and these resulted in achieving 100% utilization of the active material (111mAh/g specific capacity for the cell) at moderate C-rates. The cathode with 60% of PTMA exhibited larger ohmic resistance and lower chargedischarge properties due to the thicker layer of insulating polymer. The maximum discharge capacities at very high C-rates of 30 and 50C were realized from the 20% PTMA cathode that has the highest carbon content and hence the lowest ohmic resistance. The Li/PTMA cells exhibited good performance on long-term cycling at 1C, irrespective of the PTMA content in the cathode.
Very Efficient Nucleophilic Aromatic Fluorination Reaction in Molten Salts: A Mechanistic Study
장성우,박성우,이병세,지대윤,송충의,이성열 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.3
We report a quantum chemical study of an extremely efficient nucleophilic aromatic fluorination in molten salts. We describe that the mechanism involves solvent anion interacting with the ion pair nucleophile M+F− (M = Na, K, Rb, Cs) to accelerate the reaction. We show that our proposed mechanism may well explain the excellent efficiency of molten salts for SNAr reactions, the relative efficacy of the metal cations, and also the observed large difference in rate constants in two molten salts (n-C4H9)4N+ CX3SO3 −, (X=H, F) with slightly different sidechain (-CH3 vs. -CF3).