• Journal of the Korean Chemical Society
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• v.35 no.4
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• pp.362-367
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• 1991

Rates of nucleophilic substitution reaction ([Pd (ONN) Cl] + Y$^-\;{\rightleftharpoons}$ [Pd (ONN)Y] + Cl$^-$ ; Y = SCN$^-$, CN$^-$, N$_3^-$, imidazole, pyridine) have been measured in methanol by spectrophotometric method at various temperatures. A set of nucleophilic reactivity constants, n$_{Pd}^{\circ}$ has been calculated. These values show an order of nucleophilicity CN$^-$ > SCN$^-$ > N$_3^-$ > Imidazole > Pyridine. The enthalpy of activation are small positive values and the entropy of activation are large negative values. From these results, it can be inferred that the nucleophilic substitution reaction proceeds through an associative (A) mechanism.

• Journal of the Korean Chemical Society
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• v.33 no.2
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• pp.225-231
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• 1989

The heterogeneous rate constants for the electrochemical reduction by $trans-[Co(en)_2X_2](ClO_4)_n$(where X is cyanide, nitrite, ammonia, and isothiocyanate) at mercury and glassy carbon electrode were investigated by cyclic voltammetry, DC polarography, and by using rotating disk electrode. The good linear relationship was obtained between the activation energy of reduction and absorption wave number of complexes on glassy carbon electrode. At mercury electrode, $NO_2^-$ ligated complex showed the large deviation from the linear relationship. The difference in the value of rate constants for $NO_2^-$ ligated complex between mercury and glassy carbon electrode was about three order of magnitude which was much larger than the other complexes. It was suggested that $NO_^-$ ligated complex was reduced by inner-sphere mechanism on mercury electrode from the larger value of activation energy and entropy on mercury than carbon electrode.

• Journal of the Korean Chemical Society
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• v.24 no.2
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• pp.150-154
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• 1980

Kinetic studies of the reaction of benzyl benzenesulfonate with pyridine in acetone were carried out by the electric conductivity method under 1 to 2000 bars and at 20 to $40^{\circ}C$. The rate increases with increasing pressure and temperature. The activation enthalpy $({\Delta}H^{\neq}),\;entropy\;({\Delta}S^{\neq})$ and activation volume $({\Delta}V^{\neq})$ of the reaction are obtained by the above experiment. The isokinetic relationship between $({\Delta}H^{\neq})\;and\;({\Delta}S^{\neq})$ for pressure change in the reaction was shown, and its isokinetic temperature was $342^{\circ}K$. From all of the above results it was found that this reaction precedes on the $S_N2$ reaction mechanism in which the rate of the reaction was determined by $C{\cdots}N$ bond formation at transition state.

• Journal of the Korean Chemical Society
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• v.28 no.2
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• pp.95-101
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• 1984

Aquation reaction kinetics of $[Cr(en)_2Cl_2]^+$complex was carried by the electric conductivity method. Its temperature range was $15^{\circ}C$ to $30^{\circ}C$ and pressure was varied up to 2,000 bars. The reaction rate was increased with increasing temperature, but was reversed to increasing pressure. The activation volume(${\Delta}V^{\neq}$) was increased with increasing temperature and decreased with increasing pressure. At $25^{\circ}C$ and 1 bar it was fairly small positive value, $1.82cm^2/mole$. Activation entropy change(${\Delta}S^{\neq}$) $was calculated as small negative value,-9.019 eu, at $25^{\circ}C$ and 1bar. Referring to the thermodynamic parameters, it was estimated that aquation reaction was proceeded by the interchange-dissociation(Id) mechanism.

• Applied Biological Chemistry
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• v.33 no.4
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• pp.325-329
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• 1990

This study was undertaken to determine thermodynamic characteristics of B. subtilis p-4 and B. licheniformis p-5 proteases isolated from fermented anchovy paste. $K_m$ values of two proteases for casein as a substrate were 0.38mM in p-4 protease and 0.18mM in p-5 protease, respectively. Denaturation constants($K_D$) of p-4 and p-5 proteases were $12.2{\times}10^{-5}/sec\;and\;19.0{\times}10^{-5}/sec\;at\;40^{\circ}C,\;and\;35.7{\times}10^{-5}/sec\;and\;46.3{\times}10^{-5}/sec\;at\;50^{\circ}C$, respectively. Activation energies($E_a$) of p-4 and p-S pmteases were 19.6 Kcal/mole and 15.2kcal/mole, respectively. Free energy of activation(${\Delta}G^*$), activation enthalpy(${\Delta}H^*$) and activation entropy(${\Delta}S^*$) at $40^{\circ}C$ were 23.21Kcal/mole, 18.98Kcal/mole and -13.50 eu, respectively for p-4 protease and 22.93Kcal/mo1e, 14.58Kcal/mole and -26.68 eu, respectively for p-5 protease. The major amino acids in p-4 protease(151 residues of amino acid) were Gly, Glu, Pro, Asp, Ser, Ala, Lys and Leu, while those in p-5 protease(247 residues of amino acid) were Gly, Glu, Asp, Ala and Leu. It may be concluded that heat denaturation of two proteases showed liner regression curve and p-5 protease was more sensitive to heat than p-4 protease.

• Journal of the Korean Chemical Society
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• v.34 no.2
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• pp.117-122
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• 1990

The rate constants for the aquation of $trans-[CoETECl_2]^+ \;and \;cis-{\beta}-[CoTETCl_2]^+$ and the isomerization of $trans-[CoETEClOH_2]^{2+}$ were measured by spectrophotometric method under various temperature and pressure conditions. For the aquations of $trans-[CoETECl_2]^+ \;and\; cis-{\beta}-[CoTETCl_2]^+$, the activation entropies are 4.0 eu and 5.3 eu respectively and the activation volumes are $-5.8 cm^3mol-1\; and\; -6.6 cm^3mol^{-1}$ at 40$^{\circ}C$, respectively. From these data the dissociative mechanism involving trigonal bipyramid-type intermediate is proposed for the acquation reaction. For the isomerization of $trans-[CoETEClOH_2]^{2+}\; to\; cis-{\beta}-[CoETEClOH_2]^{2+}$ the activation entropy is 9.5 eu and the activation volume is $8.4 cm^3mol^{-1}(30^{\circ}C$. The mechanism of isomerization may be considered as the dissociative mechanism with $H_2O$-dissociation.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.154-155
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• 2006

This study investigated a mechanism for controlling the shape of Cu nanocrystals fabricated using the polyol process, which considers the thermodynamic transition from a facetted surface to a rough surface and the growth mechanisms of nanocrystals with facetted or rough surfaces. The facetted surfaces were stable at relatively low temperatures due to the low entropy of perfectly facetted surfaces. Nanocrystals fabricated using a coordinative surfactant stabilized the facetted surface at a higher temperature than those fabricated using a non-coordinative surfactant. The growth rate of the surface under a given driving force was dependent on the surface structure, i.e., facetted or rough, and the growth of a facetted surface was a thermally activated process. Surface twins decreased the activation energy for growth of the facetted surface and resulted in rod- or wire-shaped nanocrystals

• Bulletin of the Korean Chemical Society
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• v.11 no.4
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• pp.309-313
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• 1990

The rates of solvolysis of trans-$[Co(N-eten)_2Cl_2)$+ (N-eten; N-ethylethylenediamine) have been investigated using spectrophotometric method in binary aqueous mixtures containing methyl alcohol, isopropyl alcohol, t-butyl alcohol, ethylene glycol and glycerol. The values of ${\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$ obtained from temperature effect on the rate constants were $80{\sim}84 kJmol^{-1}$ and $- 28{\sim} - 45 JK^{-1}mol^{-1}.$ Extrema found in the variation of the enthalpy and entropy of activation with solvent composition correlated very well with extrema in the variation of the physical properties of mixture which relate to sharp change in the solvent structure. The reaction mechanism was discussed in terms of correlation diagrams involving the exess molar Gibbs function of mixing for the binary mixtures. The behavior of this cobalt(Ⅲ) complex was compared with that of t-butyl chloride. The application of free energy cycle to the process initial state to transition state in water and in the mixture showed that the solvation of transition state had dominant effect on the rates in the mixtures. It was found that $S_N1$ character was increased with increasing the content of co-solvent in the mixture.

• Elastomers and Composites
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• v.22 no.1
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• pp.20-28
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• 1987

The characteristic of the dielectric relaxation in silicone rubbers were studied in the frequency range of $1{\times}10^2{\sim}3{\times}10^6Hz$ at the temperature range of $30^{\circ}{\sim}170^{\circ}C$. As the results of the study, it has been confirmed that the silicone rubber containing the cross-linking agants of 2,5-bis(tert-butylperoxy)-2, 5-dimethyl hexane exhibit the dissipation spectra of two kind(${\alpha},\;{\beta}$ dissipation) due to the siloxane and methyl groups. Particularly, the maximum value of dielectric loss spectra of silicone rubber combinning the cross-linking agents of 0.7phr to 1.0phr are on the increasing in high frequency region, but the specimen of above 1.0phr become smaller again. The energy and the entropy of activation on the molicular motion obtained 18.32 kcal/mole and $1.48ca1/mole{\cdot}deg$ in measuring condition respectively.

• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3657-3664
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• 2012

Reactions of 1-adamantylmethyl chloroformate ($1-AdCH_2OCOCl$, 1) and 1-adamantylmethyl fluoroformate ($1-AdCH_2OCOF$, 2) in hydroxylic solvents have been studied. Application of the extended Grunwald-Winstein (G-W) equation to solvolyses of 1 in a variety of pure and binary solvents indicates an addition-elimination pathway in the majority of the solvents except an ionization pathway in the solvents of relatively low nucleophilcity and high ionizing power. The solvolyses of 2 show an addition-elimination pathway in all of the mixed solvents. The leaving group effects ($k_F/k_{Cl}$), the kinetic solvent isotope effects (KSIEs, $k_{MeOH}/k_{MeOD}$), and the enthalpy and entropy of activation for the solvolyses of 1 and 2 were also calculated. The selectivity values (S) for each solvent composition are reported and discussed. These observations are compared with those previously reported for other alkyl haloformate esters.