• Applied Chemistry for Engineering
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• v.4 no.2
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• pp.403-408
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• 1993

Hydroxypropyl chitin(HPCH) was prepared from chitin by reacting it with propylene oxide. The formation of liquid crystalline character of HPCH was investigated using halogenated organic solvents. Solid state $^{13}C$ NMR spectra for chitin and HPCH confirmed the incorporation of hydroxypropyl moiety. The degree of substitution of HPCH was around 0.8 as detected by elemental analysis. WAXD patterns of chitin and HPCH showed that an incorporation of hydroxypropyl unit in chitin contributed to reducing the crystallinity and enhancing the solubility in organic solvents. Polarized light microscopic pictures of concentrated HPCH solution showed that HPCH formed cholesteric liquid crystalline character at about 25w/v% solution in dichloroacetic acid and 1, 2-dichloroethane. Inherent viscosity of HPCH solution in a mixed solvent showed a transient decrease.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.718-722
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• 2011

2,4'-Bipyridinium dichromate [$(C_{10}H_8N_2H)_2Cr_2O_7$] was synthesized by the reaction of 2,4'-bipyridinie with chromium trioxide in $H_2O$. The structure was characterized by IR and ICP analysis. The oxidation of benzyl alcohol using 2,4'-bipyridinium dichromate in various solvents showed that the reactivity increased with the increase in the order of the dielectric constant (${\varepsilon}$), in the order : cyclohexene < chloroform < acetone < N,N'-dimethylformamide. In the presence of hydrochloric acid, 2,4'-bipyridinium dichromate effectively oxidized benzyl alcohol and its derivatives ($p-CH_3$, H, m-Br, $m-NO_2$) in N,N'-dimethylformamide. Electron-donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant (${\rho}$) was -0.65 at 303 K. The observed experimental data was used to rationalize the hydride ion transfer in the rate-determining step.

• Journal of the Korean Electrochemical Society
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• v.1 no.1
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• pp.28-32
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• 1998

The electrochemical behavior of film and charge-discharge capacity of Li-ion cell in 1 M $LiPF_6/EC:DME$ (1 : 1, by volume ratio) electrolyte solution was studied using chronopotentiometry, cyclic voltammetry, chronoamperometry, and impedance spectroscopy. The first irreversible capacity was higher than the second irrversible capacity because of solvent decomposition. Especially, passivation film that is electron insulating and ionic conducting were formed on the MPCF by solvent decomposition during the first charge. The solvated Li is co-intercalated with solvent into MPCF electrode. Part of the MPCF is expoliated during co-intercalation of solvent-Li. The MPCF ends up nonuniformly covered by a relatively thick layer of exfoliated particles embedded in a matrix of product by solvent decomposition.

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.151-154
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• 2011

Catalytic activity such as conversion and selectivity on the phenol hydroxylation over TS-1 prepared by hydrothermal method and microwave heating method, respectively, was compared and discussed for understanding the dependence of solvent such as water, methanol, acetone, respectively, during phenol hydroxylation, with hydrogen peroxide. Basic physical properties such as XRD, EDS, SEM and $N_{2}$ adsorption/desorption were determined and compared. The relationship between catalytic activity and physical properties of TS-1 was explained.

• Journal of the Korean Chemical Society
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• v.27 no.2
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• pp.95-101
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• 1983

The pseudo-first order rate constants have been obtained for the solvolysis of benzoyl cyanide in various aqueous solvent mixtures and ethanol-trifluoroethanol mixtures at 1, 5, 10, 15 and $20^{\circ}C$. Values of n in the Kivinen polt, m values of Grunwald-Winstein polt, $\beta$ values of Leffler relationship and values of m and l in the extended Grunwald-Winstein polt have been calculated and studied the transition state variation caused by solvent changes using the More O'Ferrall polt and quantum mechanical approach. It has been shown that the reaction proceed via the associative $S_N2$ mechanism, using the transition state parameters and quantum mechanical model approach.

• Analytical Science and Technology
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• v.18 no.3
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• pp.194-200
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• 2005

The N hyperfine coupling constants ($a_N$) of di-t-butyl nitroxide (DTBN) radicals in water-solvent system were measured with EPR spectroscopy. Various kinds of the solvents with different polarity such as acetone, dimethylsulfoxide (DMSO), methanol, ethanol and 1-propanol were applied and studied. Equilibrium constants for the solvation equilibrium and the solvent parameters ($E_T$, molar transition energy) of various water-solvent system were obtained from the experimental results and are presented. The $a_N$ values were plotted as a function of mole fraction of the solvent. In case of water-DMSO, water-ethanol and water-1-propanol system, slight negative deviations from the straight line were observed. In water-acetone system, the absorption wavelength (${\lambda}$) due to ${\eta}{\rightarrow}{\pi}^{\ast}$ transition increased linearly with the increase of mole fraction of acetone. The relationship between $a_N$ of DTBN and ${\lambda}$ due to ${\eta}{\rightarrow}{\pi}^{\ast}$ transition in water-acetone and water-DMSO system was examined. It was found that the electronic structure of the nitroxide radicals is stablized from the fact that the N hyperfine coupling constants of DTBN radicals are greatly unaffected in the environment of water-solvent system.

• Proceedings of the Membrane Society of Korea Conference
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• 1996.04a
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• pp.42-43
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• 1996

고분자 분미막을 이용한 분리기술은 기존의 분리기술에 비하여 에너지의 절약과 높은 분리효율 등의 장점이 있어 거의 모든 산업에 이용되고 있다. 분리막의 용도가 다양화됨에 따라서 내열성, 내약품성, 내유기용매성을 갖는 막소재의 개발이 필요하게 되었다. polyimide(PI)게의 고분자는 물리, 화학적 성능이 우수하고 내열성과 내유기용매성 등이 우수한 열가소성수지로서 film, sheet, tubular형으로 만들 수 있어 한외여과막이나 역삼투막, 기체분리막 등에 이용되고 있다. 그러나 투과속도를 높디고, fouling을 줄이기 위해서는 화학적 개질을 통해 친수성을 높이는 방법이 필요하다. 본 실험에서는 내열성과 내유기용매성이 우수한 polyetherimide계 고분자를 chlorosulfonic acid(CSA)를 이용하여 술폰화시킴으로써, 극성기의 도입에 의해 친수성이 향상된 sulfonated polyetherimide(SPEI)를 합성하였다.

• Applied Biological Chemistry
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• v.37 no.5
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• pp.397-401
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• 1994

Bioreduction with active dried baker's yeast proceeded smoothly in n-hexane, pentane or petroleum ether as an organic solvent system. Ethyl(1) and octyl 3-oxohexanoate(2) were reduced to $({\underline{R}})-ethyl(3)$ and $({\underline{S}})-octyl$ 3-hyroxy-hexanoate(4) with high enantiomeric excess, respectively.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.514-517
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• 2011

Herein, we fabricated magnesium oxalate nanostructures by chemical etching of a magnesium foil in alcoholic solvents containing acidic media. Interestingly, we could obtain magnesium oxalate nanowires in ethanolic oxalic acid. Growth mechanism for magnesium oxalate nanowires was investigated in terms of etching time. Annealing conditions were determined from TGA results. Magnesium oxalate nanowires were converted to magnesium oxide nanowires by thermal treatment and the magnesium oxide nanowires were examined by FE-SEM and FT-IR measurement.

• Membrane Journal
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• v.12 no.4
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• pp.240-246
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• 2002

New polysulfone scintillation proximity membranes were prepared by impregnating Cerium Activated Yttrium Silicate (CAYS), an inorganic fluor, in a membrane structure. The membranes were applied to detect the radionuclide contamination directly without the aid of a scintillation cocktail. The preparation of membranes was divided into two processes. A supporting polymer film was made of casting solutions consisting of polysulfone and solvent, their cast film being solidified by vacuum evaporation. CAYS-dispersed polymer solutions were cast over the first, solidified polymer films and coagulated either by evaporating solvent or by exchanging solvent in the solution with nonsolvent in a coagulation bath. The prepared membranes had two distinguished, but tight1y attached, double layers: one is the supporting layer of dense polymer film and the other the detecting layer consisting of CAYS and polymer. The radionuclide counting results revealed that the prepared membranes were efficient to monitor radioactivity contamination with reliable counting ability.