• 분석과학
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• 제8권4호
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• pp.481-486
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• 1995

Quenching experiments by photoinduced electron transfer between a charged donor and a neutral acceptor were carried out in acetonitrile, dichloromethane and mixed solvents of acetonitrile and dichloromethane. Tris(2, 2'-bipyridine) ruthenium(II) ($[Ru(bpy)_3]^{2+}$) which has 2+ charge and dicyanobis (2, 2'-bipyridine) ruthenium(II) ($Ru(bpy)_2(CN)_2$) which has no charge were used as electron donors, and a series of tris(${\beta}$-diketonato) ruthenium (III) was used as acceptor. In dichloromethane, $[Ru(bpy)_3]^{2+}$ and its counter ions ($ClO{_4}^-$) form ion pair. In the estimate of ${\Delta}G$ of electron transfer, the electrostatic potential between counter ions and product ion pair produced by electron transfer must be taken into account. A similar effect of counter ions was found in mixed solvents of 10, 30, 50, 70 and 90% acetonitrile ratio in volume. The effect of counter ion on ${\Delta}G$ became smaller with the increase in acetonitrile ratio. The result in mixed solvents suggests that $[Ru(bpy)_3]^{2+}$ and its counter ions form ion pair even in 90% acetonitrile solution.

• 한국전기전자재료학회논문지
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• 제28권1호
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• pp.12-16
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• 2015

$(Na,K)NbO_3$-based piezoelectric ceramics were synthesized by a solid phase sintering method with various milling solvents. The solvents were varied with acetone, ethanol, and pure water to investigate the effect on the microstructure and electrical properties. NKN ceramics showed the maximum values of the relative density (94%), the mechanical quality factor (Qm: 78) and the electro-mechanical coupling factor ($k_p$: 0.25) at the ethanol solvent. It might mean that a solid phase sintering of the NKN piezoelectrics with a suitable solvent could improve the relative density and the piezoelectric properties.

• 대한화학회지
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• 제10권3호
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• pp.119-128
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• 1966

The glass electrode was empirically calibrated in methanol-and 2-propanol-water mixed solvents, by means of which the pH-meter reading could be converted to stoichiometric hydrogen ion concentration. The thermodynamic dissociation constants of hydrogen cupferrate in methanol-and 2-propanol-water solution were potentiometrically determined with the changes in composition of organic solvents at 0.01 and 0.05 of the ionic strength and 25$^{\circ}C$. The empirical formula of the constants with mole fraction (n) of the organic solvent are as follow: methanol-water solution $pK_a$= 2.24n + 4.29 at ${\mu}$ = 0.01 n = 0.0476∼0.642 $pK_a$ = 2.35n + 4.38 at ${\mu}$ = 0.05 n= 0.0446~0.642 2-propanol-water solution $pK_a$= 5.50n + 4.48 at ${\mu}$ = 0.05 n = 0.0253~0.259 The relationships between $pK_a$ of acetic acid, propionic acid and HCup and dielectric constant of some mixed solvents were discussed. It would be considered that the factors effecting $pK_a$ value of weak acid in mixed-solvent are not only dielectric constants but acid-base character and solvation effect of the solvent, etc.

• 한국균학회지
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• 제11권3호
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• pp.115-119
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• 1983

Aspergillus phoenicis에 의한 progesterone의 전환반응에 대하여 고찰하였다. 본 실험조건에서의 물질대사 결과 $11{\alpha}-hydroxyprogesterone$이 주생성물로 생성 되었다. $11{\alpha}-hydroxyprogesterone$의 농도는 반응시간에 따라 서서히 증가하였으나 40시간 이후부터는 점근값에 도달하였다. 반응액에의 glucose 첨가는 progesterone의 전환반응 속도를 증가시켜 점근값의 농도에 도달하는 시간이 괄목할 만큼 앞당겨졌다. Progesterone의 초기 농도를 증가시키는 것은 전환율이나 반응완결에 소요되는 시간에 큰 변화를 주지 않았으나 전환반응은 progesterone 농도에 대하여 1차반응 형태로 요약될 수는 없었다. 유기용매에 의한 효소 활성의 저하정도는 유기용매의 종류 및 그 농도에 의존하였으며, 낮은 유기용매의 농도에서는 acetone이 가장 높은 전환율을 나타내었다.

• 한국식품영양과학회지
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• 제20권6호
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• pp.590-595
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• 1991

In order to investigate polar lipid ingredients and fat쇼 acid compositions in corn embryo, lipids were extracted with n-hexane (HX), pet. ether (PE), chloroform-methanol (2:1, v/v) (CM), dichoromethane-methanol (2:1, v/v DM) and hexane-diethyl ether (5:1, v/v HD). Of the glycolipid in polar lipids were separated by thin layer chormatogarphy (TLC), monoglycosyl diacyglycerol was most efficient with CM, HD, and monoglycosy sterol and monoglycosyl ceramide were similar to five solvents, but HX, PE and DM, HD were somewhat superior, respectively. Of the phospholipid, phosphatidyl inositol was most efficient with CM, DM, and phosphatidyl choline was similar to five solvents as well. Phosphatidyl serine was superior PE, HD, CM to HX, and phosphatidyl ethanolamine was inferior CM to HX. The major fatty acid in the glycolipid was linoleic acid, and it was most efficient with CM the same as plamitic acid, but oleic acid was superior in using HX, PE. The major fatty acids in the phospholipid were palmitic, heptadecanoic aicds, and they were superior in using HX and PE, respectively. Also oleic acid was most efficient with HX and CM, but HD was somewhat inferior.

• Bulletin of the Korean Chemical Society
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• 제26권1호
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• pp.139-145
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• 2005

Artificial neural networks (ANNs), for a first time, were successfully developed for the modeling and prediction of solvent effects on rate constant of [2+2] cycloaddition reaction of diethyl azodicarboxylate with ethyl vinyl ether in various solvents with diverse chemical structures using quantitative structure-activity relationship. The most positive charge of hydrogen atom (q$^+$), dipole moment ($\mu$), the Hildebrand solubility parameter (${\delta}_H^2$) and total charges in molecule (q$_t$) are inputs and output of ANN is log k$_2$ . For evaluation of the predictive power of the generated ANN, the optimized network with 68 various solvents as training set was used to predict log k$_2$ of the reaction in 16 solvents in the prediction set. The results obtained using ANN was compared with the experimental values as well as with those obtained using multi-parameter linear regression (MLR) model and showed superiority of the ANN model over the regression model. Mean square error (MSE) of 0.0806 for the prediction set by MLR model should be compared with the value of 0.0275 for ANN model. These improvements are due to the fact that the reaction rate constant shows non-linear correlations with the descriptors.

• 대한화학회지
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• 제40권6호
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• pp.415-419
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• 1996

수소결합, 유전효과 그리고 입체효과는 케톤의 카르보닐 신축진동을 결정하는 요인이 된다. 케톤의 카르보닐 신축진동은 다양한 용매에서 케톤의 농도변화에 영향을 받는다. 비극성용매에서 카르보닐 신축진동은 케톤의 부피%가 증가함에 따라 낮은 파수로 이동하고 극성용매에서는 높은 파수로 이동한다. 용매 아세토니트릴에서 카르보닐 신축진동은 dimethyl ketone을 제외하고 케톤의 부피%가 증가함에 따라 높은 파수로 이동한다. 용매의 극성이 증가할수록 카르보닐 신축진동은 낮은 파수로 이동하고 혼합용매 $CHCI_3CCI_4$에서 부피%가 증가할수록 낮은 파수로 이동한다.

• Bulletin of the Korean Chemical Society
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• 제34권1호
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• pp.211-220
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• 2013

The characteristic fluorescence properties of quercetin (QCT) and apigenin (API) were studied in various $CH_3OH-H_2O$ and $CH_3CN-H_2O$ mixed solvents. The structure of QCT is completely planar. API is not planar at the ground state but becomes nearly planar at the excited state. If the molecules are excited to the $S_1$ state in organic solvents, QCT exhibits no fluorescence due to excited state intramolecular proton transfer (ESIPT) between the -OH and the carbonyl oxygen, but API shows significant fluorescence because ESIPT occurs slowly. If the molecules are excited to the $S_2$ state, both QCT and API exhibit strong $S_2{\rightarrow}S_o$ emission without any dual fluorescence. As the $H_2O$ composition of both solvents increases, the fluorescence intensity decreases rapidly due to the intermolecular hydrogen bonding interaction. The theoretical calculation further supports these results. The change in fluorescence properties as a function of the solvatochromic parameters was also studied.

• Food Science and Biotechnology
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• 제15권3호
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• pp.482-484
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• 2006

The antioxidant activity of Bacillus polyfermenticus SCD was studied by partially purified culture extracts using various methods: ammonium sulfate precipitation, adsorption to Diaion HP-20 columns using polar solvents, and extraction using non-polar solvents. The 1,1-diphenyl-2-picyrylhydrazyl (DPPH) radical scavenging activity of these partially purified fractions was then investigated. The precipitate isolated using 75%-saturated ammonium sulfate was shown to contain about 77.2% DPPH radical scavenging activity. Using the Diaion HP-20 resin adsorption method, the fraction obtained using 60% ethanol and 60% methanol possessed 76.7 and 89.5% DPPH radical scavenging activity, respectively. Fractions obtained by extracting with the non-polar solvents 80 mg/mL chloroform, 80 mg/mL n-hexane, 80 mg/mL ethyl acetate, and 80 mg/mL butanol contained 68.4, 75.0, 70.7, and 87.5% DPPH radical scavenging activity, respectively. Further study is needed to characterize the antioxidant substance(s) released by B. polyfermenticus SCD cultures.

• Bulletin of the Korean Chemical Society
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• 제12권4호
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• pp.429-433
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• 1991

The photoinduced electron transfer reactions of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) in various polar solvents were studied by measuring time-resolved fluorescence. The temperature dependence on the fluorescence decay rate in acetonitrile, methanol, ethanol and buthanol was carried out to obtain the activation energy and Arrehnius factor for the photoinduced electron transfer reaction. It was found that as the dielectric constant of the solvent increases, the activation energy and the reaction rate increase. This implys that the Arrehnius factor is important in controlling the photoinduced electron transfer reaction rate. In water, TMPD exists in three forms (cationic, protonated and neutral forms) due to the high dielectric constant and strong proton donating power of water. The photoinduced electron transfer reaction was found to be very fast (< 50 ps) and also the long liverd component in the fluorescence decay profile attributable to the photoexcited protonated form of TMPD was observed. Probably, the reaction pathway and the reaction coordinate seem to be different depending on the solvents studied here.