• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1289-1289
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• 2001

Water-methanol and water-acetonitrile mixtures are frequently used as HPLC solvent system and strong hydrogen bonding is well-known. But a detailed aspect of water-methanol and/or water-acetonitrile mixtures have not been shown with direct spectral evidence. Recently, near infrared spectroscopy and chemometric data refinery have been successfully combined in many applications. On the basis of factor analytical methods, the spectral features of water-methanol and water-acetonitrile mixtures were studied to reveal the detail of mixtures. Water-methanol and water-acetonitrile mixtures were prepared with varying concentration of each constituent and near infrared spectral data were acquired in the range of 1100-2500nm with 2-nm interval. The data matrices were analysed with ITTFA(Iterative Target Transform Factor Analysis) algorithm implemented as MATLAB codes. As a result, the concentration profiles of water, methanol and water-methanol complex were resolved and the spectra of water-methanol complexes were calculated, which cannot be acquired with pure complexes. A similar result was obtained with NIR spectral data of water-acetonitrile mixtures. Moreover, pure spectra of hydrogen-bonding complexes of water-methanol and water-acetonitrile can be computed, while any other usual physical methods cannot isolated those complexes for acquiring pure component spectra.

• YAKHAK HOEJI
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• v.48 no.1
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• pp.6-12
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• 2004

Near-infrared spectra of methanol-water mixtures and acetonitrile-water mixtures were acquired to find interactions between solvents widely used for reverse-phase liquid chromatography. Mixtures were prepared to give a series of increasing mole fractions of methanol or acetonitrile in water. Data matrices of acquired spectra were analyzed to determine the proper number of principal components of each mixture system using Malinowski's factor indicator function. Initial guess of score matrix and loading matrix were calculated by nonlinear iterative partial least squares (NIPALS) algorithm for faster computation. Iterative target transform factor analysis (ITTFA) was applied to convert the initial estimation of score matrix to true concentration profile and loading matrix to pure spectra of pure components of the mixtures. In case of methanol-water the number of principal components was found to be 4 and those initial guess of factors were converted to the pure spectra of water methanol and two kinds of complexes. In case of acetonitrile-water the number of pure components of the mixtures was found to be 3 and the pure spectrum of acetonitrile-water complex was found. The nonlinear characteristics of concentration profiles of complexes in the solvent mixtures may give a good criteria in understanding their elution characteristics in reverse-phase liquid chromatogrsphy.

• Bulletin of the Korean Chemical Society
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• v.18 no.9
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• pp.1017-1021
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• 1997

Solvolyses of p-methoxyphenyl 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 p-methoxyphenyl chloroformate with YCl (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. 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 carbonyl addition-elimination.

• Fire Science and Engineering
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• v.29 no.2
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• pp.39-43
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• 2015

The flash point is the major property to characterize fire and explosion hazard of liquid mixtures. The flash point is the lowest temperature at which a liquid gives off enough vapor to form a flammable air-vapor mixture. The flash points of two aqueous mixtures, water-methanol and water-ethanol, were measured using Seta flash closed cup tester. A prediction method based on activity coefficient models, Wilson and UNIQUAC equations, was used to calculate the flash point. The calculated flash points were compared to the results by the calculating method using Raoult's law. The calculated values based on activity coefficients models were found to be better than those based on the Raoult's law.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2377-2381
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• 2007

Solvolyses of 3,4-dimethoxybenzenesulfonyl chloride (DSC) in water, D2O, CH3OD, and in aqueous binary mixtures of acetone, acetonitrile, 1,4-dioxane, ethanol, methanol, and 2,2,2-trifluoroethanol (TFE) have been investigated at 25.0 oC. Kinetic solvent isotope effects (KSIE) in water and in methanol and product selectivities in alcohol-water mixtures are also reported. The Grunwald-Winstein plot of first-order rate constants for the solvolyic reaction of DSC with YCl shows marked dispersions into separated lines for various aqueous mixtures. With use of the extended Grunwald-Winstein equation, the l and m values obtained are 1.12 and 0.58 respectively for the solvolyses of DSC. The relatively large magnitude of l is consistent with substantial nucleophilic solvent assistance. From Grunwald-Winstein plots the rate data are dissected approximately into contributions from two competing reaction channels. This interpretation is supported for alcohol-water mixtures by the trends of product selectivities, which show a maximum for ethanol-water mixtures. From the KSIE of 1.45 in methanol, it is proposed that the reaction channel favored in methanolwater mixtures and in all less polar media is general-base catalysed and/or is possibly (but less likely) an addition-elimination pathway. Also, the KISE value of 1.35 for DSC in water is expected for SN2-SN1 processes, with minimal general base catalysis, and this mechanism is proposed for solvolyses in the most polar media.

• Bulletin of the Korean Chemical Society
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• v.17 no.6
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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.

• Journal of the Korean Chemical Society
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• v.13 no.1
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• pp.9-12
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• 1969

Partial molal volumes of anilinium chloride in several methanol-water mixtures have been determined at $30.0^{\circ}C$. The maximum in limiting slopes and the minimum in partial molal volumes at 0.4 mole fraction have been interpreted as the result of maximum electrostriction of the solvent with the minimum free volume.

• Bulletin of the Korean Chemical Society
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• v.19 no.9
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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.

• Journal of the Korean Chemical Society
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• v.37 no.8
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• pp.695-701
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• 1993

Rate constants of solvolysis of 2-thiophenesulfonyl chloride were determined in aqueous binary mixtures with methanol, ethanol, acetone in water and in methanol. These data are interpreted using the equation of Grunwald-Winstein and Kivinen relationship. Also, kinetic solvent isotope effects in water and in methanol and product selectivities in alcohol-water mixtures were determined. Kinetic solvent isotope effect for hydrolysis of 2-thiopenesulfonyl chloride was 2.24 and 1.47 for methanol and water, respectively. Selectivity values for formation of ester relative to acid in ethanol-water mixtures show maximum S value. From kinetic solvent isotope effect in methanol and water, selectivity data in aqueous alcoholic solvents and solvent effects, it is proposed that the reaction channel favoured in low polarity solvents is general-base catalysis and/or is possibly addition elimination (S$_A$N) reaction pathway and in high polarity solvents iS S$_N$2 reaction mechanism.

• Bulletin of the Korean Chemical Society
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• v.23 no.10
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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