• Bulletin of the Korean Chemical Society
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• v.24 no.6
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• pp.792-796
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• 2003

Polychlorinated dibenzo-p-dioxins (PCDDs) are extremely toxic and persistent environmental pollutants. Their chemical reactivities and other physicochemical/biological properties show a strong dependence on the chlorination pattern. With increasing the number of chlorines, dioxin congeners become more electronegative and gain higher electron affinities. The vertical electron affinities (VEA) are related with the LUMO energies of neutral molecules. LUMO energies of all PCDD congeners were calculated at the B3LYP/6-31G** level and those of some selected congeners at the level of B3LYP/6-311G**//B3LYP/6-31G** and B3LYP/cc-pvtz/ /B3LYP/6-31G**. The total energies of neutral and anionic species for dibenzo-p-dioxins (DD), 1469-TCDD, 2378-TCDD, and OCDD were calculated at the level of B3LYP/6-31G**, B3LYP/aug-cc-pvdz, and B3LYP/ aug-cc-pvtz//B3LYP/6-31G**. By using the four congeners with D2h symmetry as reference molecules, we could estimate VEA (B3LYP/aug-cc-pvdz) of 75 PCDD congeners based on the linear correlations between LUMO energy and VEA (B3LYP/6-31G**) and between VEA (B3LYP/6-31G**) and VEA (B3LYP/aug-ccpvtz// B3LYP/6-31G**). Results show that all PCDDs with the number of Cl ≥ 3 have positive electron affinities. The PCDD electron affinity values provided in this work can be a useful data set in understanding the congener-specific reactivities of dioxins in various environmental media.

• Journal of the Korean Chemical Society
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• v.32 no.3
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• pp.260-266
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• 1988

The rate constants for the nucleophilic addition reactions of thioglycolic acid and cysteine to ${\beta},\;{\beta}$-dichlorostyrene derivatives(p-H, p-Cl, $p-CH_3,\;and\;p-OCH_3$) were photochemically determined at various pH and a rate equation which can be applied over a wide pH range was obtained. On the bases of rate equation, general base catalysis and substituent effect, the plausible addition reaction mechanism was proposed: Above pH 9.0, the reaction was initiated by the addition of sulfide anion, and in the range of pH 7.0 to 9.0, the neutral molecules and it's anions attacked to the double bond, competitively. However, below pH 7.0, only the neutral molecules of thioglycolic acid or cysteine added to the carbon-carbon double bond.

• Biotechnology and Bioprocess Engineering:BBE
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• v.5 no.2
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• pp.136-140
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• 2000

A sensitive and quantiative method for the structural analysis of oligosaccharide was established for the glycoform analysis of glconproproteins. Inthis study, n-linked oligosaccharides of human IgG and bovine transferin were analyzed for the evaluation of the methydrate moiety ofthe method. Chrbohydrate moiety of glycoprotein was relased by hydrazinolysis and purified by paper chromatography. The oligosaccharides were labeled with a fluorescent bye, 2-aminobenzamide, for the enhancement of detection sensitivity. sialylated (acidic) oligosaccharides were separated from neutral oligosaccharide by employing a strong anion-exchange column(MonoQ) followed by the treatment with sialidase. Enzymatically desiayated fractions and neutral fractions of oligosaccharides were applied to normal-phase HPLC to resolve the peaks according to glucose unit (GU). The structure of separated molecules was further determined by sequential digestion with exoglycosidases. As a result, disialylated biantennary complextype oligosaccharide was found to be a major sugar chain in bovine transferrin (63%). In human IgG, core fucosylated asialobiantennary complex oligosaccharides were dominant. These results coincided well with reported results.

• Analytical Science and Technology
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• v.12 no.6
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• pp.478-483
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• 1999

Coagulation efficiencies of some organic compounds by aluminum based coagulants including alum, PAC, PACS were studied. The coagulation efficiency was highest at the neutral pH. It was decreased with an order of PACS, PAC, and alum at the neutral pH. The organic compounds of high molecular weights showed good coagulation efficiencies with all coagulants, while the small molecules were not coagulated. Organic compounds having more than two adjacent functional groups of OH and COOH showed coagulation efficiencies of 10~80%.

• Textile Coloration and Finishing
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• v.13 no.2
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• pp.114-119
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• 2001

Four kinds of neutral sodium salts with different anions, NaF, NaCl, NaBr, and NaI, were added to the dye bath to accurately understand the effect of anions on the reactive dyeing of silk with C. I. Reactive Black 5. The sodium cation towered the negative surface potential of the silk and increased the dye-uptake on fille fabric as reported previously. However, because of the discrepancy in the anions'inhibition power from cation's lowering: the surface negative potential the amount of the dye on the silk fiber was different from each other in the order of $F^->Cl^-> Br^-I^-$. The activation energy(E$_{a}$) lot the dyeing was in the order of $F^->Cl^-> Br^-I^-$ but the dye-uptake on the fabric and the activation free energy$(\Delta{G}^*)$, the real energy barrier fort the reaction, were in the order of $F^->Cl^-> Br^-I^-$ because the strength of the interaction of the anions with sodium cations was the salute as the order of the latter. In other words F$^{[-1000]}$ exerted the weakest electrostatic force on $Na^+$ and competed with the dyestuff anions least of all. The decrease in $\Delta{S}^*$ may be due to the looesly bonded activated complex of dyestuff anions, sodium cations and fiber molecules at transition state. It was clarified from the Brёnsted equation that sodium salts with different anions also had fille ionic strength effect and the specific salt effect on the reactive dyeing.g.

• Textile Coloration and Finishing
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• v.12 no.6
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• pp.372-379
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• 2000

Four kinds of neutral salts with different cations, LiCl, NaCl, KCl, and CsCl, were added to the dye bath to accurately understand the effect of cations on the reactive dyeing of silk with C. I. Reactive Black 5. The cations of salts added lowered the negative surface potential of the silk, improving equilibrium adsorption and the accessibility of the dyestuff to the fiber greatly and speeding up the dyeing rate in the order of $Li^+>Na^+>K^+>Cs^+$. The activation energy$(E_a)$ for the dyeing was in the order of$Li^+>Na^+>K^+>Cs^+$ but the activation free energy$(\Delta{G}^*)$, or the real energy barrier for the reaction, was in the order of $Li^+>Na^+>K^+>Cs^+$ because the degree of the contribution of E$^{a}$ to the activation entropy$(\Delta{S}^*)$ was $Li^+>Na^+>K^+>Cs^+$. It was found from this result that LiCl had the strongest lowering effect on the negative surface potential of silk. The decrease in $\Delta{S}^*$ should be attributed to the loosely bonded activated complex of dyestufffs, cations and fiber molecules at transition state. It was clarified from the Bronsted equation that salts had the ionic strength effect and the specific salt effect on the reactive dyeing.

• Bulletin of the Korean Chemical Society
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• v.16 no.5
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• pp.410-416
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• 1995

The proton transfer energies of gas phase glycine and alanine and those of hydrated glycine and alanine were calculated both with Hartree-Fock and $M{\Phi}ller-Plesset$ ab initio molecular orbital (MO) calculations with 6-31G** basis set. The transition states of the proton transfer of gas phase glycine was also investigated. For zwitterions, both for glycine and alanine, the water bound to -NH3+ site stabilize the complex more compared with the water bound to -CO2-. The proton transfer energy, ΔEpt, of glycine, alanine, mono-hydrated glycine, mono-hydrated alanine, di-hydrated glycine and di-hydrated alanine were obtained as 30.78 (MP2: 22.57), 31.43, 23.99 (MP2: 17.00), 24.98, 22.87, and 25.63 kcal/mol, respectively. The activation energy for proton transfer from neutral (Nt) glycine to zwitterion (Zw) glycine, Ea, was obtained as 16.13 kcal/mol and that for reverse process, Ear, was obtained as 0.85 kcal/mol. Since the transition state of the proton transfer of gas phase glycine locate near the glycine zwitterion on the potential energy surface and the shape of the potential well of the zwitterion is shallow, the zwitterion easily changed to neutral glycine through the proton transfer.

• Membrane and Water Treatment
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• v.4 no.2
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• pp.127-142
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• 2013

In order to investigate the significance of "salting-out" and "pore swelling" effects on the nanofiltration of neutral solutes, rejection properties of two NF ceramic and polymeric membranes were studied with single polyethyleneglycol (PEG) solution and mixed PEG/inorganic electrolyte solutions. For both membranes, the rejection rate of PEG was found to decrease significantly in the presence of ions. In the case of the ceramic membrane (rigid pores), this phenomenon was imputed to the sole partial dehydration of PEG molecules induced by the surrounding ions. This assumption was confirmed by the lowering of the PEG rejection rates which followed the Hofmeister series. Experimental data were used to compute the resulting decrease in the Stokes radius of PEG molecules in the presence of the various salts. Concerning the polymeric membrane, the decrease in the rejection rate was found to be systematically higher than for the ceramic membrane. The additional decrease was then ascribed to the swelling of the pores. The experimental data of rejection rates were then used to compute the variation in the mean pore radius in the presence of the various salts. The pore swelling phenomenon due to accumulation of counterions inside pores was supported by electrokinetic charge density measurements.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.338-338
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• 2011

The behavior of hydroxide ions on water-ice films was studied by using $Cs^+$ reactive ion scattering (RIS), low energy sputtering (LES) and temperature-programmed desorption (TPD). A $Cs^+$ beam of a low kinetic energy (<100 eV) from $Cs^+$ ion gun was scattered at the film surface, and then $Cs^+$ projectiles pick up the neutral molecules on the surface as $Cs^+$-molecule clusters form (RIS process). In LES process, the preexisting ions on the surface are desorbed by the $Cs^+$ beam impact. The water-ice films made of a thick (>50 BL) $H_2$O layer and a thin $D_2O$ overlayer were controlled in temperatures 90~140K. We prepared hydroxide ions by using Na atoms which proceeded hydrolysis reaction either on the ice film surface or at the interface of the $H_2O$ and $D_2O$ layers.[1] The migration of hydroxide ions from the $H_2O/D_2O$ interface to the top of the film was examined as afunction of time. From this experiment, we show that hydroxide ions tend to reside at the water-ice surface. We also investigated the H/D exchange reactions of $H_2O$ and $D_2O$ molecules mediated by hydroxide ions to reveal the mechanism of migration of hydroxide to the ice surface.

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3420-3424
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• 2013

The reaction of $LnCl_3{\cdot}7H_2O$ [Ln = La (1), Ce (2)] with salicylic acid (HL) and 1,10-phenanthroline (Phen) at $20^{\circ}C$ in $H_2O$/ethanol gave after work-up and recrystallization two novel lanthanide complexes with general formula $[Ln(Phen)_2(L)_3(HL)]{\cdot}H_2O$. Compounds 1 and 2 were characterized by IR and UV-Vis spectroscopy, TGA, CHN as well as by X-ray analysis. According to these results, compounds 1 and 2 are isostructural and contain $Ln^{3+}$ ions with coordination number nine. Complexes 1 and 2 consist of two Phen, one neutral HL and three L anions (two L anions act as monodentate ligands and the third one is chelating to $Ln^{3+}$). Thermal decomposition led to primary loss of the Phen molecules. Then HL molecules and finally L moieties left the material to give $Ln_2O_3$.