• Journal of the Korean Chemical Society
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• v.32 no.6
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• pp.528-535
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• 1988

The rates of oxygen ring formation of $[Mo_2O_3(Ox)_2(OxH)_2(NCS)_2]$ have been investigated spectrophotometric method in binary aqueous mixtures. Temperature was $20^{\circ}C$ to $40^{\circ}C$ and pressure was varied up to 1500 bar. The observed rate constants are increased by hydrogen ion and decreased by thiocyanate. The more increasing of co-solvents dielectric constant, the more stable intermediate is formed. The observed rate constant is given by, $k_{obs}^{-1} = k^{-1} (1 + K^{-1}[H_2O]^{-1}) All activation parameters are positive values. The oxygen ring formation of [Mo_2O_3(Ox)_2(OxH)_2(NCS)_2]$ is believed to be a interchange-dissociative mechanism..

• Journal of the Korean Chemical Society
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• v.33 no.3
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• pp.309-314
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• 1989

A kinetic study was carried out for the redox reaction of cis-$[Co(en)_2(N_3)_2]^+$ with Fe(II) in acidic solution by spectrophotometric methods. This redox reaction system have been found to show a third order for overall reaction as the respective first order with respect to reactant cis-$[Co(en)_2(N_3)_2]^+$, Fe(II), and $H^+$ catalyst. The activation parameters, ${\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$, were obtained as 14.2Kcal/mol and -16.7 e.u., respectively. On the basis of the kinetic data, we suggest that the redox reaction system proceeds via inner sphere mechanism. The rate equation derived from the proposed mechanism is in agreement with the observed rate equation.

• Journal of the Korean Chemical Society
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• v.54 no.4
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• pp.374-379
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• 2010

The interaction of dichlorophenol isomers with the micellar system of TTAB (tetradecyltrimethylammonium bromide) was studied by the UV/Vis spectrophotometric method. The solubilization constants ($K_s$) of dichlorophenol isomers into the micellar system have been measured with the change of temperature and the various thermodynamic parameters have been calculated and analyzed from these changes. The results show that the values of ${\Delta}G^{\circ}_s$ and ${\Delta}H^{\circ}_s$ are all negative within the measured temperature range. The effects of additives (n-butanol and NaCl) on the solubilization of dichlorophenol isomers have been also measured. There was a great change on the values of $K_s$ and CMC simultaneously with these additives. From these changes we can postulate the solubilization sites of each isomers in the micellar system of TTAB.

• Journal of the Korean Chemical Society
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• v.30 no.1
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• pp.3-8
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• 1986

The investigation of the effect of solvent structure on the first-order solvolysis of cis-$[Co(en)_2ClNO_2]^+$ion has been extended to water + co-solvent mixtures where the co-solvents are glycerol, ethylene glycol, isopropyl alcohol and t-butyl alcohol. Rates of solvolysis have been evaluated by spectrophotometric method at temperature 25∼30$^{\circ}$C. The polarity of solvent has influence on the variation of rate constant. The non-linear plot of the rate constant in log scale versus $\frac{D-1}{2D+1}$ implies that change in solvent structure with composition plays an important role in determining the variation of rate constant. The linearity of the plot of the rate constant in log scale versus the Grundwald-Winstein Y factor confirms that the solvolysis is an Id-type process with considerable extension of the metal chloride bond in the transition state. In the Kivinen equation the slope of the plot of log k versus $log(H_2O)$ suggests that the solvolysis is also an Id-type process. The application of free energy cycle shows that the effect of solvent structure is greater in the transition state than in the initial state.

• Journal of the Korean Chemical Society
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• v.30 no.1
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• pp.90-100
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• 1986

Along with synthesizing a model oligodeoxyribonuclotide GpApApTpTpCp which had the EcoRI recognition site according to "Phosphotriester Method", reported methods for protecting functions, condensation, deprotection, purifying products, quantification and identification were evaluated and modified. It was realized that oligomers were efficiently synthesized by elongating by dimer unit per step of the condensation and the condensation yields were decreased with increased numbers of the residues. The problems of quantification/identification involved in the oligonucleotide synthesis using small amount of the reactants were solved by employing UV/IR spectrophotometry and hplc/tlc. It was also proved that a nucleotide having the exposed 5'-OH function was well synthesized by condensing a 5'-OH nucleotide and a phosphodiester nucleotide whose molar ratio was intendedly made to be 1 : 1.2 and then detritylating followed by washing with an aqueous solution of sodium bicarbonate. Spectrophotometric and chromatographic data of the nucleotides and their derivatives concerned in this synthetic work were prepared.

• Journal of the Korean Chemical Society
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• v.25 no.1
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• pp.1-6
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• 1981

Ultraviolet spectrophotometric investigations were carried out on the systems of o-, m-and p-xylene with iodine in carbon tetrachloride. The results reveal the formation of one to one molecular complexes of the type, $C_6H_4(CH_3)_2{\cdot}I_2. $The equilibrium constants of complexes were obtained in consideration of that absorption maxima has the blue shift with the increasing temperatures according to the formation of the charge transfer complexes. The thermodynamic parameters, $ {\Delta}$H, $ {\Delta}$G and $ {\Delta}$S for the formation of the charge transfer complexes were calculated from these values. These results combined with previous study of this series indicated that the relative stabilities of the polymethylbenzene complexes with iodine increase in the order, Benzene < Toluene < o-Xylene < p-Xylene These results are supposed to be the influence resulted from increase of electron density by the positive inductive effect and the steric hindrance effect.

• Journal of the Korean Chemical Society
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• v.38 no.8
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• pp.590-597
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• 1994

The chemical behavior of the trivalent lanthanide$(Pr^{3+}, Eu^{3+}, Gd^{3+} 그리고 Yb^{3+})$complexes with organo-ligand (2,2,6,6-tetramethyl-3,5-heptanedione) has been investigated by the use of UV/Vis-spectrophotometric, magnetics, and electrochemical method. The two or three energy absorption bands are observed by the spectra of these complexes. The magnetitude of crystal field splitting energy, the spin pairing energy and bond stength was obtained from the spectra of the complexes. These are found to be localization, low-spin (or high-spin state, and strong bonding strength. The magnetic dipole moment are found to be diamagnetic complexes (or paramagnetic). The electrochemical behavior of complexes was observed by the use of cyclic voltammetry in aprotic media. These reduction peaks were irreversible two and three step reduction processes by electron transfer.

• Journal of the Korean Chemical Society
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• v.36 no.1
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• pp.44-50
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• 1992

The ability to account for magnetic and spectra properties of complexes was investigated for the splitting of the degenerate d-orbitals and with nonaqueous solution by UV/vis-spectrophotometric method. The correlation of the magnetitude of 10Dq obtained from the spectra, the pairing energy, and the spin state of the complexes. The electrochemical behavior of complexes were investigated by the use of cyclic voltammetry in aprotic media. These reduction peak of $[(C_6H_5)3_P]_2Pd(II)(CH_3COO)_2$ and $[(C_6H_5)_3Pd]_2Pd(II)Cl_2$ were irreversible one-electron processes at peak $E_{pc1} = -1.32 V,\;E_{pc2} = -1.56 V$ and $E_{pc1} = -1.74 V,\;E_{pc2} = -1.88 V$ of these complexes vs. Ag/AgCl, but nickel complexes were not to be reducible.

• Food Science of Animal Resources
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• v.36 no.2
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• pp.194-197
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• 2016

The alkaline phosphatase (ALP) assay is a rapid and convenient method for verifying milk pasteurization. Since colorimetric ALP assays rely on subjective visual assessments, their results are especially unreliable near the detection limits. In this study, we attempted to establish quantitative criteria for residual ALP in milk by using a more objective method based on spectrophotometric measurements. Raw milk was heat-treated for 0, 10, 20, 30, and 40 min and then subjected to ALP assays. The quantitative criteria for residual ALP in the milk was determined as 2 μg phenol/mL of milk, which is just above the ALP value of milk samples heat-treated for 30 min. These newly proposed methodology and criteria could facilitate the microbiological quality control of milk.

• Korean Journal of Medicinal Crop Science
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• v.3 no.1
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• pp.21-24
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• 1995

Vitamin contents in three different types of the fruits and seeds of Rosa davurica Pall. were determined to examine their applicability for a new health food products as well as medical supplies. HPLC analysis of the fruits showed that circular(L) type fruits contained the highest ascorbic acid (AA) concentration (911mg/1000g). Elliptical and circular(S) type fruits contained a little less amounts of AA, their concentrations being 358mg/l00g and 344mg/100g, respectively. Spectrophotometric analysis of total ${\beta}-carotene$ contents in the fruits showed a similar amount of ${\beta}-carotene$ in elliptical (286mg/100g) and circular(L) (208mg/100g) type fruits, but a far less amount was shown in the circular(S) type fruits (24 mg/100g).