• Bulletin of the Korean Chemical Society
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• 제17권6호
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• pp.520-524
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• 1996

Solvolyses of phenyl chloroformate in water, D2O, CH3OD, 50% D2O-CH3OD, and in aqueous binary mixtures of acetone, ethanol and methanol are investigated at 25.0 ℃. Product selectivities are reported at 25 ℃ for a wide range of ethanol-water and methanol-water solvent compositions. The Grunwald-Winstein plots of first-order rate constants for phenyl chloroformate with YCl (based on 2-adamantyl chloride) show marked dispersions into three separate lines for the three aqueous mixtures with a small m value (m< 0.2) and a rate maximum for aqueous alcohol solvents. Third-order rate constants, kww, kaw, kwa and kaa were calculated from the observed kww and kaa values together with kaw and kwa calculated from the intercept and slope of the plot of 1/S vs. [alcohol]/[water]. The calculated rate constants, kcalc and mol % of ester agree satisfactorily with those of the observed rate constants, kobs and mol % of ester, supporting the stoichiometric solvation effect analysis. The kinetic solvent isotope effects determined in water and methanol are consistent with the proposed mechanism of the general base catalyzed and/or carbonyl addition for phenyl chloroformate solvolyses based on mass law and stoichiometric solvation effect studies.

• 대한화학회지
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• 제25권2호
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• pp.67-74
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• 1981

벤조산, 파라메톡시벤조산 및 파라니트로벤조산의 산해리상수를 $25^{\circ}C$에서 메탄올의 무게퍼센트가 0, 10, 20, 30, 40, 50, 65 및 80%인 에탄올-물 혼합용매중에서 직접 전도도를 측정하는 방법과 약산의 시료를 과염소산용액으로 적정하면서 전도도를 측정하는 방법으로 구하고, 이 두가지 방법으로 구한 결과를 검토하고 다른 방법과 비교하였다.

• Bulletin of the Korean Chemical Society
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• 제19권9호
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• pp.968-973
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• 1998

Solvolyses of para-substituted phenyl chloroformates in water, $D_2O,\;CH_3OD$, 50% $D_2O-CH_3OD$, and in aqueous binary mixtures of acetone, ethanol, methanol are investigated at 25.0 ℃. Product selectivities are reported for a wide range of ethanol-water and methanol-water solvent compositions. These data are interpreted using the Grunwald-Winstein relationship, Hammett equation, and quantum mechanical model. Grunwald-Winstein plots of the first-order rate constants for phenyl chloroformates with $Y_{Cl}$ (based on 1-adamantyl chloride) show marked dispersions into three separate curves for the three aqueous mixtures with a small m value and a rate maximum for aqueous alcohol solvents. To account for these results, third-order rate constants, $k_{ww},\;k_{aw},\;k_{wa}$, and $k_{aa}$ were calculated from the observed $k_{ww}\;and\;k_{aa}$ values together with $k_{aw}\;and\;k_{wa}$ calculated from the computer fit. The kinetic solvent isotope effects determined in water and methanol are consistent with the proposed mechanism of the general base catalyzed carbonyl addition-elimination for para-substituted phenyl chloroformates solvolyses based on mass law and stoichiometric salvation effect studies. This study has shown that the quantum mechanical model predicts transition state variation correctly for $S_N2\;like\;S_AN$ reaction mechanism of para-substituted phenyl chloroformates.

• Bulletin of the Korean Chemical Society
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• 제23권10호
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• pp.1445-1450
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• 2002

Solvolytic rate constants at 25 $^{\circ}C$ are reported for solvolysis of chlorodithioformate (1) in binary mixtures of water with acetone, ethanol, methanol, methanol-d, 50%methanol-d/50%D2O, and 2,2,2-trifluroethanol (TFE), and also in TFE-ethanol mixtures. The Grunwald-Winstein plot shows that the three aqueous mixtures exhibit dispersions into separate line. The correlation is improved only slightly by additional parameters NT for solvent nucleophilicity and/or I for aromatic ring parameter. Rate ratios in solvents of the same $Y_cl$ value, having different nucleophilicity provide measures of the minimum extent of nucleophilic solvent assistance, and the value of 3.35 for $[$k_{40EW}$/$k_97TFE$]_Y$ (EW = ethanol-water), is consistent with an essentially SN1 reaction mechanism. This study has shown that the magnitude of l, m and h values associated with a change of solvent composition is able to predict the SN1 reaction mechanism. log(k/$k_o$) = mY + lN + hI

• 통합자연과학논문집
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• 제14권3호
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• pp.99-106
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• 2021

A mixture of alcohol and water is commonly used as antifreeze, liquor, and the fundamental solvents for the manufacture of cosmetics, pharmaceuticals, and inks in our daily life. Since various properties of alcohol water mixtures such as density, boiling or melting point, viscosity, and dielectric constant are determined by their mixing ratio, it is very important to know the mixing ratio to predict their properties. One of simple method to find the mixing ratio is measuring the density of the mixtures. However, it is not easy to predict the mixing ratio from the density of the mixtures because the relationship between mixing ratio and density has not been established well. The relationship is dependent on the relative sizes of solute and solvent molecules, and their interactions. Recently, an empirical model to predict the density of glycerol water mixture from their mixing ratio has been introduced. The suggested model is simple but quite accurate for glycerol water mixture. In this article, we investigated the applicability of this model to different alcohol water mixtures. Densities for six different alcohol water mixtures containing various alcohols (e.g., ethylene glycol, 1,3-propane diol, propylene glycol, methanol, ethanol, and 1-propanol) were simulated and compared to experimentally measured ones to investigate the applicability of the model proposed for glycerol water mixtures to other alcohol water mixtures. The model predicted the actual density of all alcohol water mixtures tested in this article with high accuracy at various ratios. This model can probably be used to predict the mixing ratio of other alcohol water mixtures from their densities beyond 6 alcohols tested in this article from their densities.

• 청정기술
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• 제24권3호
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• pp.239-248
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• 2018

본 연구에서는 (주)파인텍에서 개발한 제올라이트 4A 분리막을 이용하여 물, 에탄올, 이소프로필알코올 단일 성분 및 혼합물의 투과증발 실험을 수행하였다. 본 분리막은 수열합성법을 이용하여 제막하였고, Si/Al 비율이 1인 LTA 구조에 $Na^+$를 이온교환하여 약 $4{\AA}$의 기공크기를 갖고 있으며, 강한 친수성을 나타내고 있다. 물리적 특성을 확인하기 위해 SEM, porosimetry, BET, 압축강도계를 이용하였다. 다양한 온도 및 농도 조건 실험을 통해 제올라이트 4A 분리막이 물/에탄올(분리계수 3,000 이상) 및 물/이소프로필알코올(분리계수 1,500 이상) 혼합물로 부터 물을 선택적으로 분리할 수 있음을 확인하였다. 활동도계수, Generalized Maxwell Stefan 모형 및 Dusty Gas 모형을 이용하여 단일성분 및 혼합물의 투과증발 거동을 모사하였으며, Genetic Algorithm를 이용한 상수추정을 통하여 분리층의 흡착 및 확산상수를 구하였다.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 1992년도 제1차 학술발표초록집
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• pp.27-27
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• 1992

• 대한화학회지
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• 제10권1호
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• pp.11-14
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• 1966

Ethanol-water mixture 內에서 일어나는 p-nitrobenzyl chloride의 solvolysis反應에 대한 熱力學的 parameter를 구하고 이 data를 ${\delta}_M{\Delta}H^{\neq} = a'Y + b{\delta}_M{\Delta}S^{\leq}$에 適用함으로써 反應常數 a'가 50% 이하의 alcohol solvent에서나 50% 이상의 solvent에서 같다는 것을 알 수 있었다. 즉 water-rich solvent에서나 alcohol-rich solvent에서나 solvolysis反應의 mechanism은 변함이 없다는 것을 알았다.

• 산업기술연구
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• 제20권A호
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• pp.179-184
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• 2000

The surface of porous alumina membrane was modified with silane coupling agent in order to enhance hydrophobicity. The contact angle of water to the surface-modified alumina membrane was greater than $90^{\circ}$. The surface-modified membrane was tested in vapor permeation for the concentration of aqueous ethanol. With the increase of ethanol concentration in the feed, permeation flux increased due to the greater affinity of ethanol with surface-modified alumina membrane than that of water. The experimental results showed that the permeation rate of surface-modified alumina membrane was 15~1000 times greater than that of polymer membranes.

• 대한화학회지
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• 제24권1호
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• pp.1-7
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• 1980

메탄올, 에탄올 및 에탄올-물 혼합용매중에서 메틸클로로휘메이트, 메틸티올클로로휘메이트, 메틸티오노클로로휘메이트 및 메틸디티오클로로휘메이트의 가용매분해반응에 대한 속도상수를 전기전도도법으로 구하고 활성화 파라미터를 계산하였다. 결과로 메틸클로로휘메이트는 항상 $S_N2$ 메카니즘으로 반응하며, 가수분해 순위는 $CH_3S(CS)Cl>CH_3S(CO)Cl>CH_3O(CS)Cl>CH_3O(CO)Cl$ 로 $S_N1$ 반응성이 감소하고, 메탄올에서는 $CH_3S(CS)Cl$은 $S_N1$으로, 기타는 $S_N2$로 반응하고, 에탄올에서는 모두 $S_N2$로 반응하나 아직도 메틸클로로디티오휘메이트는 $S_N1$ 반응성이 어느정도 작용함을 알았다. 또한 에탄올-물 혼합용매에서 물함량이 큰 부분에서는 티오치환체의 $S_N1$ 반응성이 증가하며 메틸클로로디티오휘메이트는 $S_N1$으로 반응함을 알았다. 에탄올-물 혼합용매중에서 $S_N1$ 반응성의 순위는 가수분해속도의 순위와 같았다.