• Journal of the Korean Chemical Society
• /
• v.30 no.3
• /
• pp.265-272
• /
• 1986

Kinetic studies for the methanolysis of tert-butyl halides (t-BuCl, t-BuBr, t-BuI) were carried out in MeOH-1,1,2,2-tetrachloroethane mixtures. The solvatochromic comparison method was used with six indicators to analyze solvent effects on the ionizations of tert-butyl halides. It was shown that the cooperative effect of solvent polarity-polarizability was the most important factor influenced on the methanolysis rates of tert-butyl halides, but the electrophilic assistance for halide leaving group and the nucleophilic assistance for tert-butylium ion were considerably influential, too. And it was found that the electrophilic assistance caused by hydrogen bonding and the nucleophilic assistance for carbon center were stronger for more basic leaving group ($I^-) and more polarizable leaving group(t-BuCl

• Journal of the Korean Chemical Society
• /
• v.46 no.6
• /
• pp.528-534
• /
• 2002

We have studied to find the optimum electrolyte that satisfied high ionic conductivity, large elec-trochemical window, etc in Li-ion battery. And also studied were the effect of a passive film on carbon anode surface,which is formed by solvent decomposition during the initial charge process. Electrochemical properties of the passive film formed on carbon anode surface investigated and explained as the volumetric ratio of the mixed solvents. The results of scanning electron microscopy, chronopotentiometry, cyclic voltammetry, impedance spectroscopy revealed that the electrochemical properties of the passive film were varied with the ionic conductivity of the electrolyte including the mixed solvents.

• Journal of the Korean Chemical Society
• /
• v.27 no.3
• /
• pp.167-177
• /
• 1983

The kinetics of 2-anthracenesulfonyl chloride in methanol-water, ethanol-water, acetone-water and acetonitrile-water has been studied by electroconductometric method. For media in which water has the same mole fraction, the rate was greater in protic solvent than in dipolar aprotic solvent and it was greater consistently in methanol-water than in ethanol-water over the whole range of solvent composition investigated, while the two rates in acetone-water and acetonitrile-water inverted at about 0.9 of mole fraction of water. Both m value, susceptibility of rate to the ionizing power and n value, solvent participation number in the transition state were much smaller in protic solvent. These values and the activation parameters show that solvolysis of 2-anthracenesulfonyl chloride proceeds by $ S_N2$ mechanism.

• Applied Chemistry for Engineering
• /
• v.8 no.6
• /
• pp.967-972
• /
• 1997

Recovery of aromatics in extract phase which was obtained by batch equilibrium extraction between light cycle oil(LCO) and dimethylsulfoxide(DMSO) solution as solvent was investigated by re-extraction. To select the most suitable re-extraction solvent for recovery of aromatics in extract phase, distribution equilibrium was measured between extract phase and solvents. The solvents used were benzene(B), toluene(T), m-Xylene(mX), n-hexane(Hx) and n-hexane(Hx) and n-Octane(Ot). From the distribution coefficients and yields of aromatics, Hx seemed to be the most suitable. Furthermore, effects of operation parameters for re-extraction of aromatics in the extract phase were studied by batch equilibrium re-extracion with Hx as solvent. Yields of aromatics were found to increase with increasing solvent/feed (extract phase) mass ratio(S/F), while distribution coefficients of aromatics were fixed irrespective of S/F used. Operating temperature did not affect distribution coefficients and yields of aromatics. Distibution coefficients and yields of naphthalene group(carbon numer : 10~12) increased with increasing cabon number. Mass transfer rates of aromatics were also measured with a batch stirred vessel.

• Journal of the Korean Chemical Society
• /
• v.32 no.2
• /
• pp.85-93
• /
• 1988

Solvolyses of t-butylhalides (X = Cl, Br, I) in quasi isodielectric solvent system, MeOH-nitromethane, MeOH-nitrobenzene and MeOH-ethyleneglycol have been studied kinetically. Methanolyses for t-butylhalides in MeOH-NM and MeOH-NB show rate maxima at 40~100 % (v/v) MeOH. The rate maxima observed have been interpreted as a result of cooperative enhancement of polarity-polarizability and hydrogen bonddonor ability of solvents. The influences of polarity-polarizability and hydrogen bonddonor ability on reactivities of substrates have been discussed in terms of Y value changes. The solvolysis rates for t-butylhalides in E.G. are more than 20 fold faster than those in MeOH and this was attributed to the solvent structure of E.G.

• Journal of the Korean Chemical Society
• /
• v.27 no.1
• /
• pp.1-8
• /
• 1983

Solvent effects on nucleophilic substitution reaction of naphthalene sulfonyl chlorides with pyridine in protic and aprotic solvent have been studied by means of conductometry. Results showed that the rate constants increased with dielectric constants for protic solvents, while they decreased with dielectric constants for aprotic solvents, except for acetonitrile which has a higher dielectric constant but had also greater rate constant. The rate constants were shown to be more susceptible to polarity-polarizability parameter, , than to hydrogen bond donor acidity parameter, ${\alpha}$, indicating that the pulling effect of hydrogen bonding solvent.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
• /
• 2003.10a
• /
• pp.142.2-142
• /
• 2003

손바닥 선인장(Opuntia ficus indica)은 중심자목 선인장과에 속하는 다년생 초본으로 열매는 서양배 모양이며 많은 종자가 들어있고 다량의 점질물을 함유하고 있다. 손바닥 선인장 열매(prickly pear pulp)는 14.5%의 고형분 함량을 가지고 있으며, 0.21%의 단백질, 0.12%의 지방, 0.44%의 회분, 0.19%의 pectin 이외에 미량의 비타민 A와 C 그리고 여러 종류의 무기질을 포함하고 있다. 주요 당류로서 sucrose(68.7%), fructose(18.0%) 및 glucose(12.8%)를 함유하고 있으며, 점질다당류의 구성분인 mannose 가 0.5% 포함되어 있다. 손바닥 선인장 열매는 높은 혈중 콜레스테롤, 염증 및 비만 등의 치료에 유용한 것으로 알려져 있다. 본 연구에서는 손바닥 선인장 열매 추출물의 기능적 특성을 반응표면분석에 의해 모니터링 하였다. 그 결과 환원당 함량은 최대값이 33.39 mg%로 추출온도 69.87$^{\circ}C$, 추출시간 68.84 min및 시료에 대한 용매비 16.29 ml/g일 때였다. 총 플라보노이드 함량은 추출온도 89.7$0^{\circ}C$, 추출시간 170 min 및 시료에 대한 용매비 17.07 ml/g일 때 2,03 mg%로 최대값을 나타내었다. 펙틴 함량은 추출온도 96.54$^{\circ}C$, 추출시간 135.28 min및 시료에 대한 용매비 20.02 nWg일 때 최대값 82.04 mg%를 나타내었으며, 비타민 C 함량은 추출온도 61.8$0^{\circ}C$, 추출시간 101.98 min 및 시료에 대한 용매비 12.14 ml/g일 때 최대값이 3.76 mg%였다.

• Journal of the Korean Wood Science and Technology
• /
• v.44 no.1
• /
• pp.124-134
• /
• 2016

The main goal of this study was to investigate biomodification mechanism of lignin by white rot fungus, Abortiporus biennis, and to depolymerize ethanol organosolv lignin for industrial application. In nitrogen-limited culture, A. biennis polymerized mainly lignin showing a rapid increase of molecular weight and structural changes depending on incubation days. At the initial incubation days, cleavage of ether bonds increased phenolic OH content, while the results were contrary in of the later part of the culture. Based on these results, ascorbic acid as a reducing agent was used to induce depolymerization of lignin during cultivation with white rot fungus. As a result, the degree of increase of average molecular weight of lignin was significantly declined when compared with those of the ascorbic acid free-experiment, although the molecular weight of fungus treated sample slightly increased than that of control. Furthermore, lignin derived oligomers in culture medium were depolymerized with the addition of ascorbic acid, showing that the average molecular weight was 381 Da, and phenolic OH content was 38.63%. These depolymerized lignin oligomers were considered to be applicable for industrial utilization of lignin. In conclusion, A. biennis led to the polymerization of lignin during biomodification period. The addition of ascorbic acid had a positive effect on the depolymerization and increase of phenolic OH content of lignin oligomers in medium.

• Journal of the Korean Ceramic Society
• /
• v.25 no.5
• /
• pp.50-50
• /
• 1988

The controlled Ti(CO2H5)4 hydrolysis reactions for the synthesis of Spherical Monodispersed Titania powders are described. Increasing the concentration of TEOT and the molar ratio of water to TEOT in alcohol solution decrease the reaction time and the particle size. The reaction time is delalyed by increasing the chain length and the number of carbon branches of alcohol as a solvent. The prepared powders with an average diameter of 0.8μ and the spherical monodispersed transfer to Rutile phase at 550℃.

• Applied Chemistry for Engineering
• /
• v.16 no.4
• /
• pp.507-512
• /
• 2005

When carbon electrode is used as an anode in Li ion battery, passivation film forms on the electrode surface during the initial charge process due to so called Solid-Electrolyte Interphase (SEI). The passivation film formed by solvent decomposition during the initial charge process affects charge/discharge capacity. In this paper, 1 M $LiPF_6,EC:DEC$ (1 : 1, volume ratio) electrolyte with $Li_2CO_3$, at various temperatures, the electrochemical characteristics of passivation film formed on Kawasaki Mesophase Fine Carbon electrode surface were investigated by using chronopotentiometry, cyclic voltammetry, and impedance spectroscopy. Experimental observations indicated that as solvent decomposition occurred, the decomposition voltage was strongly dependent on ionic conductivity, which was low in the process at low temperature. The impedance of passivation film formed during the initial charge process, were dependent on the temperature.