• Journal of the Korean Chemical Society
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• v.51 no.1
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• pp.21-30
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• 2007

A multiwavelength spectrophotometric titration method was applied to study protolytic constants of four water-soluble vitamins, folic acid(vitamin B9 or B0), thiamine(vitamin B1), riboflavin(vitamin B2) and pyridoxal (vitamin B6) in binary ethanol-water mixtures at 25oC and an ionic strength of 0.1M NaNO3. The protolytic equilibrium constants, spectral profiles, concentration diagrams and also the number of components has been calculated from the curve fitting of the pH-absorbance data with appropriate mass balance equations by an established factor analysis model. DATAN program was used for determination of acidity constant and SPECFIT program was used for calculation of standard deviations and partial correlation coefficients. A glass electrode calibration procedure based on the four parameter equation pH=α+SpcH+JH+[H+]+ JOH-Kw/[H+] based on the Gran,s plots was used to obtain pH-readings in the concentration scale (pcH). The effect of the solvent on the protolytic constants was discussed.

• Journal of the Korean Chemical Society
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• v.27 no.6
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• pp.411-418
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• 1983

The effects of existing anions in hydrofluoric acid solutions, $F^-$ and $HF_2$on the extraction of methylene blue-$BF_4^-$ ion-pair into 1,2-dichloroethane have been investigated by spectrophotometry. The absorbance of the extracted ion-pair is found to be independent of $F^-$ion up to $10^{-2}$ molar concentration, which implies that $F^-$ion dose not directly interfere with the extraction. However, $HF_2^-$ ion competes with $BF_4^-$ion for methylene blue and the extraction constant for methylene blue-H$F_2$ion-pair is calculated to be 8.5 at $25^{\circ}C$.

• Journal of the Korean Chemical Society
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• v.22 no.3
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• pp.150-157
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• 1978

The rate constants for the hydrolysis of the derivatives of N-(p-nitrophenyl)-benzohydrazonyl azide (p-$CH_3,\;p-CH_3O,\;p-NO_2$, p-Cl, p-Br) have been determined by UV spectrophotometry in 50% dioxane-water at $25^{\cicr}C$ and a rate equation which can be applied over wide pH range was obtained. Below pH 5, the rate of hydrolysis of hydrazonyl azides is accelerated by electron-donating group ($\rho$ = -0.47), whereas at the pH values greater than 7, the $\rho$-value is 0.68. The effect of salt, solvent, substituent and azide ion on the rate of hydrolysis are rationalized in terms of $S_N1$ and $S_N2$ mechanism; below pH 5, the hydrolysis proceed through $S_N1$, however, above pH 7, the hydrolysis is started by the attack of hydroxide ion and in the range of pH 5∼7, these two reactions occur competitively.

• Journal of the Korean Chemical Society
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• v.22 no.1
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• pp.30-36
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• 1978

The kinetics of hydrolysis of ${\alpha}$-nitrobenzaldehydephenylhydrazone derivatives (p-$NO_2$, m-$NO_2$, p-Cl, p-$CH_3$) have been investigated by UV spectrometry in 25% dioxane-water at $25^{\circ}C$ and a rate equation which can be applied over wide pH range was obtained. From the rate equation and the effect of solvent, substituent and pKa on the rate equation, the following reaction mechanisms were proposed. Below pH 3.0 the hydrolysis of ${\alpha}$-nitrobenzaldehydephenylhydrazone proceeds by $S_N1$ mechanism, while above pH 4.0 the hydrolysis proceeds through 1,3-dipole ion mechanism. In the range of pH from 3.0 to 4.0 these two reactions occur competitively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.6039-6046
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• 2013

Cr(VI)-heterocyclic complex[Cr(VI)-2-methylpyrazine] was synthesized by the reaction between of heterocyclic compound(2-methylpyrazine) and chromium trioxide, and characterized by IR and ICP analysis. The oxidation of benzyl alcohol using Cr(VI)-2-methylpyrazine in various solvents showed that the reactivity increased with the increase of the dielectric constant(${\varepsilon}$), in the order : cyclohexene${\rho}$) was Cr(VI)-2-methylpyrazine= -0.65(308K). The observed experimental data have been ratiolized. The hydride ion transfer causes the prior formation of a chromate ester in the rate-determining step.

• Journal of the Korean Applied Science and Technology
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• v.31 no.4
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• pp.602-611
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• 2014

The critical micelle concentration (CMC) of the zwitterionic surfactant of dodecyldimethyl(3-sulfopropyl)ammonium hydroxide(LSB, $CH_3(CH_2)_{11}N^+(CH_3)_2(CH_2)_3SO{_3}^-$) and LSB/Tween-20, LSB/Tween-40, LSB/Tween-80 and LSB/DTAB, LSB/TTAB, LSB/CTAB mixed surfactant systems were determined by using the UV/Vis absorbance method from 284 K to 312 K. And the effects of temperature on the micellization have been measured for the thermodynamic study. The results show that the measured values of gibbs free energy are all negative in the whole measured. The values of enthalpy are positive Tween-20, And negative other surfactants. but the values of entropy are positive in the whole measured temperature region. The results show that all of the thermodynamic parameters are dependent on temperature and alkyl-group's length.

• Journal of the Korean Chemical Society
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• v.35 no.5
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• pp.569-574
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• 1991

Six free base porphyrins were synthesized by reacting pyrrole with benzaldehyde or its derivatives and then reacted with metal chlorides to prepare corresponding metal complexes. In addition, polymer-bonded porphyrins were synthesized by treating chloromethylated styrene-divinyl benzene (1%) copolymer beads with meso-tetra (p-aminophenyl)porphyrin (TNPP) solution and then treated with cupric chloride to obtain Cu(Res-NH-TPP-$NH_2$). The porphyrin compounds were characterized by visible, inffrared and electron spin resonance spectral analyses. The metal contents of metalloporphyrins were determined by atomic adsorption spectrophotometry. The synthesized porphyrin compounds were subsequently examined for their catalytic strength and found the activity to increase in the following order: free base porphyrins; metalloporphyrins; polymer-bonded metalloporphyrin. Among metalloporphyrins, Cu-TNPP showed the greatest catalytic power.

• Journal of the Korean Chemical Society
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• v.33 no.6
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• pp.607-613
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• 1989

The chemical equilibria of Ni(II)-tetraamine (tetraamine = 2,12-dimethyl-3,7,11,17-tetraazabicyclo-11,3,1-heptadeca-1(17),2,11,13,15-pentaene) complex ion in water, acetonitrile, acetone and nitromethane were investigated using spectrophotometric method, respectively. The equilibria between low-spin ($D_{4h}$) and high-spin ($O_h$) structures of Ni-tetraamine complex ion were presented in water, acetonitrile and acetone, but not in nitromethane. The eqilibrium constants, the reaction enthalpies and the reaction entropies were determined from analysis of the temperature dependence of the electronic spectra. The formation of the triplet species ($O_h$) was found to be exothermic. The solvent and electrolyte effects on the equilibrium constants could be explained by the dielectric constants of solvents and the reaction entropies.

• Journal of Life Science
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• v.12 no.2
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• pp.144-150
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• 2002

This experiment was designed to investigate the antioxidant effects of Chrysanthemum coronarium L. (CC) fractions on the liposomal phospholipid membranes. The sample CC was extracted and fractionated into five different types, methanol (CCMM), hexane (CCMH), ethylacetate (CCMEA), butanol (CCMB), and aqueous (CCMA) fractions. The antioxidant activities of CC fractions in oxidized dilinoleoylphosphatidylcholine (DLPC) liposomes were examined by spectrophotometry measuring conjugated dienes. The oxidation indices of five CC fractions exhibited weaker antioxidant activities than that of BHT in oxidized DLPC liposomes, however, showing much similar antioxidant activities of $\alpha$-tocopherol in the oxidized DLPC liposomes, which is known as a potent antioxidant. Among CC fractions, CCMM and CCMA in oxidized DLPC liposomes showed rather effective than $\alpha$-tocopherol after 2 h. These results strongly indicate that bioactive substances in CC fractions have a kind of function as potent antioxidants against biomembrane oxidation.

• Applied Chemistry for Engineering
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• v.21 no.3
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• pp.337-342
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• 2010

The interaction of monochlorophenol isomers with the micellar system of TTAB (tetradecyltrimethylammonium bromide) was studied by the UV/Vis spectrophotometric method. The solubilization constants ($K_s$) of monochlorophenol isomers into this micellar system have been measured with the change of temperature. Various thermodynamic parameters (${\Delta}G^{\circ}_s$, ${\Delta}H^{\circ}_s$, and ${\Delta}S^{\circ}_s$) have been calculated and analyzed from the dependence of $K_s$ values on the temperature. The results show that the values of ${\Delta}G^{\circ}_s$ and ${\Delta}H^{\circ}_s$ are all negative but the values of ${\Delta}S^{\circ}_s$ are all positive for the solubilizations of all isomers within the measured temperature range. The effects of additives (n-butanol and NaCl) on the solubilization of monochlorophenol isomers by the same surfactant system 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 isomer in the micellar system of TTAB.