• Bulletin of the Korean Chemical Society
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• 제21권5호
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• pp.503-509
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• 2000

The solvent effects on the relative free energies of solvation and the difference in partition coefficients (log P) for $Rb^+$ to $K^+$ mutation in several solvents have been investigated using Monte Carlo simulation (MCS) of statistical perturbation theory(SPT). In comparing the relative free energies for interconversion of one ion pair, $Rb^+$ to $K^+$, in $H_2O$(TIP4P) in this study with the relative free energies of the computer simulations and the experimental, we found that the figure in this study with the relative free energies of the computert simulations and the experimental, we found that the figure in this study is $-5.00\pm0.11$ kcal/mol and those of the computer simulations are $-5.40\pm1.9$, -5.5, and -5.4 kcal/mol. The experimental is -5.1 kcal/mol. There is good agreement among various studies, taking into account both methods used to obtain the hydration free energies and standard deviations. There is also good agreement between the calculated structural properties of this study and the simulations, ab initio and the experimental results. We have explained the deviation of the relationship between the free energy difference and the Onsager dielectric function of solvents by the electron pair donor properties of the solvents. For the $Rb^+$ and $K^+$ ion pair, the Onsager dielectric function of solvents (or solvent permittivity), donor number of solvent and the differences in solvation dominate the differences in the relative free energies of solvation and partition coefficients.

• 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.

• Bulletin of the Korean Chemical Society
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• 제23권7호
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• pp.929-930
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• 2002

• Bulletin of the Korean Chemical Society
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• 제19권7호
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• pp.799-802
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• 1998

• Bulletin of the Korean Chemical Society
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• 제11권6호
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• pp.568-570
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• 1990

• Archives of Pharmacal Research
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• 제27권4호
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• pp.371-375
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• 2004

The silicon linker is the foremost traceless linker used in solid-phase reactions. Hydrogen fluo-ride (HF) or trifluoroacetic aicd (TFA) can remove the silicon linker with the silicon atom being replaced by a hydrogen atom. In this experiment, the linkers 1c and 2d, which are the most useful in solid-phase reactions, were synthesized, Linker 1c is composed of seven linearly linked carbons and linker 2d includes an oxygen atom in the linear carbon chain to increase the solvation capacity. The carboxylic acid component of linker 1c and 2d forms an amide or ester bond with resin. The synthesized linkers 1c and 2d could be utilized in constructing a chemical compound library that includes indole, benzodiazepine and phenothiazine (aromatic ring compounds).

• Bulletin of the Korean Chemical Society
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• 제26권11호
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• pp.1761-1766
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• 2005

Solvolysis rates of isopropenyl chloroformate (3) in water, $D_2O$, $CH_3OD$ and in aqueous methanol, ethanol, 2,2,2-trifluoroethanol (TFE), acetone, 1,4-dioxane as well as TFE-ethanol at 10 ${^{\circ}C}$ are reported. Additional kinetic data for pure water, pure ethanol and 80%(w/w) 2,2,2-trifuoroethanol (T)-water (W) at various temperatures are also reported. These rates show the phenomena of maximum rates in specific solvents (30% (v/v) methanol-water and 20% (v/v) ethanol-water) and, variations in relative rates are small in aqueous alcohols. The kinetic data are analyzed in terms of GW correlations, steric effect, kinetic solvent isotope effects (KSIE), and a third order model based on general base catalysis (GBC). Solvolyses based on predominately stoichiometric solvation effect relative to medium solvation are proceeding in 3 and the results are remarkably similar to those for p-nitrobenzoyl chloride (4) in mechanism and reactivity.

• Bulletin of the Korean Chemical Society
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• 제24권8호
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• pp.1081-1090
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• 2003

Two different electronically resonant two-dimensional spectroscopies are described. The first, two-color photon echo peak shift spectroscopy, is sensitive to correlations in transition frequency between the initial and probed (final) states. It provides new insight into the mechanism of ultrafast solvation and should prove useful for characterizing dynamics in inhomogeneous systems in general. The second technique, fifth order threepulse scattering, contains two coherence periods whose durations are controlled. The entire two-dimensional surface was recorded for a dye molecule in dilute solution and a photosynthetic light-harvesting complex. The data provide insight into the short-time dynamics of solvation and exciton relaxation, respectively.

• Bulletin of the Korean Chemical Society
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• 제24권8호
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• pp.1069-1074
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• 2003

A theoretical description and experimental demonstration of homodyne-detected two-color transient grating (2-C TG) signal are presented. By treating the coupled bath degrees of freedom as a collection of harmonic oscillators and using a short-time expansion method, approximated nonlinear response functions were obtained. An analytic expression for the two-color transient grating signal was obtained by carrying out relevant Gaussian integrals. The initial rising and decaying parts of the 2-C TG signal is shown to be critically dependent on the ultrafast inertial component of the solvation correlation function. The experimental results confirm the predictions of the theoretical model.

• BMB Reports
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• 제36권3호
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• pp.243-250
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• 2003

In this paper we investigate (using AM1 semi-empirical as well as HF methods at the STO-3G, 3-21G, 6-31G, 6-$31G^*$ and 6-31+$G^{**}$ level) the conformations, geometrical parameters, Mulliken charges, and solvation effects of the triphosphate form of AZT (AZTTP), as well as the thymidine nucleotide (dTTP) structure. Our calculated geometrical parameters and Mulliken charges, with and without solvation effects, are correlated with recent experimental results.