• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2311-2315
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• 2011

Alumina supported polyphosphoric acid (PPA/$Al_2O_3$) was successfully prepared by impregnation of alumina support by polyphosphoric acid and characterized using FT-IR spectroscopy, the $N_2$ adsorption/desorption analysis (BET), thermal analysis (TG/DTG), and X-ray diffraction (XRD) techniques. The catalytic behavior of this new solid acid supported heterogeneous catalyst was checked in the synthesis of 14-aryl-14H-dibenzo[a, j]xanthenes by cyclocondensation reaction of ${\beta}$-naphthol and aryl aldehydes under solvent-free conditions. The results showed that the novel catalyst has high activity and the desired products were obtained in very short reaction times with high yields. Moreover, the catalyst can be easily recovered by filtration and reused at least three times with only slight reduction in its catalytic activity.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2385-2390
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• 2011

Preparation of ammonium dihydrogenphosphate supported on alumina ($NH_4H_2PO_4/Al_2O_3$) and its primary application as a solid acid supported heterogeneous catalyst to the synthesis of 1,2,4,5-tetrasubstituted imidazoles by a one-pot, four-component condensation of benzil, aromatic aldehydes, primary amines, and ammonium acetate under thermal solvent-free conditions were described. The results showed that the novel catalyst has high activity and the desired products were obtained in high yields. Furthermore, the products could be separated simply from the catalyst, and the catalyst could be recycled and reused with only slight reduction in its catalytic activity. Characterization of the catalyst was performed by FT-IR spectroscopy, the $N_2$ adsorption/desorption analysis (BET), thermal analysis (TG/DTG), and X-ray diffraction (XRD) techniques.

• Bulletin of the Korean Chemical Society
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• v.34 no.5
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• pp.1521-1524
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• 2013

N-Propylsulfamic acid supported onto magnetic $Fe_3O_4$ nanoparticles (MNPs-PSA) was used as an efficient and magnetically recoverable catalyst for synthesis of 2H-Indazolo[2,1-b]phthalazine-1,6,11(13H)-trione derivatives from the three-component, one-pot condensation reaction of phthalhydrazide, aromatic aldehydes and cyclic 1,3-diones, in good to excellent yields at $100^{\circ}C$ under solvent-free conditions. The catalyst was easily separated with the assistance of an external magnetic field from the reaction mixture and reused for several consecutive runs without significant loss of its catalytic efficiency. In order to compare, the synthesis of 2H-Indazolo[ 2,1-b]phthalazine-1,6,11(13H)-trione derivatives in the presence of catalytic amount of sulfamic acid (SA) under same reaction condition was also reported.

• Clean Technology
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• v.20 no.2
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• pp.123-129
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• 2014

A green procedure is described for the preparation of a series of ionic liquids where two 3-methylimidazolium cations were bridged with ethylene glycol chain as linkers. Diethylene glycol-bis(3-methylimidazolium) ditosylate, triethylene glycolbis(3-methylimidazolium) ditosylate, and tetraethylene glycol-bis(3-methylimidazolium) ditosylate were heated with 3-methylimidazole under solvent-free condition to give the corresponding bis(3-methylimidazolium) ditosylate ionic liquids efficiently in a short time.

• Journal of the Korean Chemical Society
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• v.14 no.1
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• pp.51-59
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• 1970

The apparent molal volumes(${\phi}_v$) of the homologous salts $RNH_3Cl$, where R varies from methyl-($CH_{3^-}$) to n-butyl-(n-$C_4H_{9^-}$) in a series of methanol-water mixtures have been determined at 30$^{\circ}C$ by means of a float method to fifth decimal places down to 0.01 m. The values of ${\phi}_r$ extrapolated to infinite dilution give partial molal volumes $\bar{V}^{\circ}$which varies considerably in accordance with the solvent composition. that is, mole fraction of methanol. The experimental results are discussed in terms of the varying size and charge effect, hydrophobic nature of the solute species, and also the additivity relationship between successive homologous and the structure of the binary solvent. The results indicate that at 0.1 mole fraction methanol the enhanced structuredness of water cause a minimum in the partial molal volumes of cations $\bar{V}^{\circ}_+$, while at 0.4 mole fraction the solvent structure is such that the free volume is a minimum but the effect of electrostriction is a maximum.

• Resources Recycling
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• v.26 no.3
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• pp.26-31
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• 2017

LIX 63 showed a selectivity for the extraction of Pd(II) over other PGMs, such as Pt(IV), Ir(IV) and Rh(III) from 6 M HCl solution. Moreover, HCl solution has significant effect on the oxidation-reduction reaction between Ir(IV) and LIX 63. Therefore, the applicability of employing LIX 63 for the separation of the 4 PGMs was investigated from 3 M HCl solution. From 3 M HCl solution, only Pd(II) was selectively extracted by LIX 63 and its extraction percentage was higher than from 6 M HCl solution. Extraction of the Pd(II) free raffinate with TBP led to the selective extraction of Pt(IV). After oxidation of Ir(III) with $NaClO_3$ to Ir(IV), extraction of the Pt(IV) free raffinate with Aliquat 336 selectively extracted Ir(IV). For each extraction step, optimum stripping conditions were obtained. By this process, it was possible to separate the 4 PGMs by solvent extraction from 3 M HCl solution.

• Journal of Life Science
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• v.18 no.2
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• pp.220-227
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• 2008

To clarify the antioxidation effect of the various solvent fractionation of Tetragonia tetragoniodes which has been known to superior plants for the traditional prevention and treatment of stomach-related diseases, total polyphenol and flavonoid contents, vitamin E content, the elimination activity of a DPPH free radical and superoxide anion, inhibition activity of the superoxide generation, reducing power and metal chelating effects were estimated. The contents of the polyphenol compounds were highest in the DCM and EA fractionation, and the content of flavonoid was high in the order of HX and EA fractionation. The vitamin E content showed high in the order of the HX and DCM fractionation among solvent fractions. $IC_{50}$ for the elimination effect of a DPPH radical were estimated as 554.25 and $394.96{\mu}g/ml$ in the DCM and EA fractions, respectively. These values were higher than that of BHT $784.7{\mu}g/ml$ widely used in antioxidation effect. The inhibition activity of the superoxide generation using the T. tetragoniodes solvent fractions represented the effects similar to that of ${\alpha}$-tocopherol known to prevent the lipoprotein oxidation, but lower consequences than that of the phenol-resins, BHT and BHA, respectively. In the antioxidation activity derived by the reducing capability, the EA fractionation in a 1.5 mg/ml concentration showed higher than that of ${\alpha}$-tocopherol.

• Bulletin of the Korean Chemical Society
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• v.29 no.2
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• pp.363-371
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• 2008

As a computational method for the discovery of the effective agonists for PPARd, we address the usefulness of molecular dynamics free energy (MDFE) simulation with explicit solvent in terms of the accuracy and the computing cost. For this purpose, we establish an efficient computational protocol of thermodynamic integration (TI) that is superior to free energy perturbation (FEP) method in parallel computing environment. Using this protocol, the relative binding affinities of GW501516 and its derivatives for PPARd are calculated. The accuracy of our protocol was evaluated in two steps. First, we devise a thermodynamic cycle to calculate the absolute and relative hydration free energies of test molecules. This allows a self-consistent check for the accuracy of the calculation protocol. Second, the calculated relative binding affinities of the selected ligands are compared with experimental IC50 values. The average deviation of the calculated binding free energies from the experimental results amounts at the most to 1 kcal/mol. The computational efficiency of current protocol is also assessed by comparing its execution times with those of the sequential version of the TI protocol. The results show that the calculation can be accelerated by 4 times when compared to the sequential run. Based on the calculations with the parallel computational protocol, a new potential agonist of GW501516 derivative is proposed.

• Journal of the Korean Chemical Society
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• v.23 no.4
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• pp.187-197
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• 1979

The molar optical rotation of poly(cis-5-methylproline) was measured in solvent mixtures of chloroform and chloroethanol. After proper allowance for time-dependent mutarota-tions, equilibrium states between form A and form B were observed to occur with a solvent composition of 0.5~10 % chloroethanol in chloroform by volume. From the equilibrium constants, which were calculated by optical rotations at equilibrium measured at three different temperatures (5, 25, and 45 $^{circ}$C), the thermodynamic parameters-free enthalpy, enthalpy and entropy changes for the mutarotation-were evaluated. It was found that starting with equimolar concentrations of form A and form B, the forward mutarotation occurred in the solvent compositions of chloroethanol greater than 3 % by volume, whereas the reverse mutarotation resulted in solvent compositions of chloroethanol less than 3 % by volume. The changes in enthalpy and entropy for the forward mutarotation were found to be positive, while those were for the reverse mutarotation were negative. The driving forces for the forward mutarotation were found to be the increase in entropy, whereas that for the reverse mutarotation was the negative enthalpy change. The thermodynamic data were explained by the interaction between polymer and solvent, i.e., preferential hydrogen bonding of chloroethanol with the carbonyl group in form B over form A, and by difference in conformational energies between form A and form B.

• The Journal of Korean Medicine
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• v.32 no.1
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• pp.141-150
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• 2011

Objectives: The aim of this study was to elucidate the antioxidant effect of solvent fractions of Angelica gigas root. Methods: The ethanol extract of Angelica gigas root was suspended in water and then partitioned with dichloromethane (MC Fr.), ethyl acetate (EA Fr.) and butanol (BuOH Fr.), sequentially. The antioxidant activities of solvent fractions of Angelica gigas root were evaluated for radical scavenging activity against stable free radicals (2,2-diphenyl-1-picrylhydrazyl) DPPH, hydrogen peroxide and superoxide anion radicals. In addition the antioxidant activities of solvent fractions of Angelica gigas root against peroxyl radicals, hydroxyl radicals and peroxynitrites were determined by the total oxy-radical scavenging capacity (TOSC) assay. Results: Among the solvent fractions of MC Fr., EA Fr., and BuOH Fr., BuOH Fr. was found to have stronger antioxidant activity with $IC_{50}$ values of 59.72, 14.36, 30.96 and $44.75\;{\mu}g/m{\ell}$ on the DPPH radical, nitrite, superoxide anion and hydrogen peroxide, respectively, than BHA used as a positive control. Moreover, specific TOSC values(564.8, 276.4 and 405.5 TOSC/mM) of BuOH fr. against peroxyl radicals, hydroxyl radical and peroxynitrite were 4 times higher than GSH (136.5, 67.4 102.6 TOSC/mM) used as a positive control. Conclusions: These results suggest that the BuOH fr. of Angelica gigas root has a high antioxidant activity and can be useful to develop functional food against oxidative stress conditions.