• Journal of the Korean Chemical Society
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• v.42 no.3
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• pp.315-322
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• 1998

A series of new dimesogenic compounds were prepared and their thermotropic and liquid crystalline properties were studied by differential scanning calorimetry and on a hot-stage of a polarizing microscope. These compounds, 1,10-bis[2,5-bis(4-substitutedphenoxycarbonyl)phenoxy]decanes, consist of two bis(ρ-substitutedphenoxy)terephthalate units interconnected through a oxydecamethyleneoxy spacer on the central terephthaloyl units resulting in the structure of "H-shaped" dimeric twin compounds. The terminal substitutent groups were changed; X=-F, -H, -I, -Cl, -Br, $-NO_2,\;-CF_3,\;-OC_4H_9,\;-CN\;and\;-C_6H_5.$ The compounds with X=$-OC_4H_9,\;-CN\;and\;-C_6H_5$ were monotropically nematic. In contrast, the compounds with $X=-F, -H, -I, -Cl, -Br, $-NO_2\;and\;-CF_3$ were non-liquid crystals. The nematic group efficiency of these compounds was in the order of -C_6H_5>-CN>-OC_4H_9.$

• Journal of the Korean Chemical Society
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• v.34 no.6
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• pp.548-554
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• 1990

Temperature effects on the fluorescence emission spectra of 0.01 M Eu(III) ion with ClO$_4$, Cl$^-$, NO$_3$ were studied. Relative intensity change of hypersensitive band ($^5D0\; {\to}\;^7F_2$) and nonhypersensitive band ($^5D0 \;{\to}\;^7F_1$) was quite remarkable with temperature and ligand. The relative intensity change was interpreted as the change of formation constant and used to calculation the enthalpy change of $Eu(H_2O)_X^{3+}$+ to EuL(H$_2O)_{X-1}^{2+}$ complex. $\Delta{H}$ of $Eu(H_2O)_X^{3+}$ to EuCl(H$_2O)_{X-1}^{2+}$ was roughly 15 kJ/mol and temperature independent, but $\Delta{H}$ of EuNO$_3(H_2O)_{X-1}^{2+}$ was changed with temperature; -11 kJ/mol at 25$^{\circ}C$ and 47 kJ/mol at 250$^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.7 no.5
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• pp.391-395
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• 1986

MNDO calculations were carried out to determine reactant complexes and transition states of the $S_N2$ reactions of $CH_3X\;+\;Y^-\;{\to}\;CH_3Y\;+\;X^-$ where X = F, Cl, CN and Y = CN, OH, F, Cl. The leaving group ability was found to vary inversely with the activation barrier, which in turn was mainly ascribable to the deformation energies accompanied with bond stretching of C-X bond and inversion of $CH_3$ group. The nucleophilicity was shown to be in the order $Cl^->F^->OH^->CN^-$ but the effect on the activation barrier was relatively small compared with that of the leaving group. The bond breaking and bond formation indices and energy decomposition analysis showed that the TS for the reaction of $CH_3$Cl occurs in the early stage of the reaction coordinate relative to that of $CH_3$F. It has been shown that the potential energy surface (PES) diagrams approach can only accommodate thermodynamic effects but fails to correlate intrinsic kinetic effects on the TS structure.

• Polymer(Korea)
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• v.24 no.3
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• pp.382-388
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• 2000

Polymer electrolyte films consisting of poly(vinylidenefluoride-hexafluoropropylene) (PVdF-HFP), LiClO$_3$ and a mixture of ethylene carbonate (EC) and ${\gamma}$-butyrolactone (GBL) were examined in order to obtain the best compromise between high ionic conductivity, homogeniety, dimensional and electrochemical stability. Measurements of ionic conductivity, differential scanning calorimetry and linear sweep voltammetry have been carried out for various compositions. The highest conductivity of 3.8$\times$10$^{-3}$ S$cm^{-1}$ / at 3$0^{\circ}C$ were obtained for a film of 30(PVdF-HFP)+7.8LiClO$_4$+62.2EC/GBL. From the DSC study, it has been found that the PVdF-HFP gels are stable up to 10$0^{\circ}C$, and the salt lowers the melting temperature of crystalline part of PVdF by interacting sensitively with polymer segments. When Lithium metal is in contact with the gel films, it tends to undergo corrosion and the reaction products accumulate resulting in the formation of a passive film on Li electrode. As the aging time progresses, the interfacial resistance increases continuously. Anodic stability is measured to extend up to about 4.5 V vs. Li.

• Analytical Science and Technology
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• v.30 no.5
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• pp.240-251
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• 2017

1,1,1,2-Tetrafluoroethane (HFC-134a), which is used as refrigerant in air conditioners, has been recently regulated as a greenhouse gas and is recommended for reuse by refining. It is very important to quantitatively analyze trace impurities present in the refrigerant to evaluate the criteria for reuse. In this study, trace impurities including C, H, Cl, and F, which are difficult to quantify because there are no reference materials, were quantitatively analyzed by a gas chromatograph-atomic emission detector (GC/AED); for this analysis, this was preceded by a qualitative analysis with a GC-mass selective detector (GC/MSD). In addition, the AED response was investigated using a hydrocarbon mixed reference material, which was proportional to the number of atoms in the component. Fifteen refrigerant components were detected as trace impurities in HFC-134a by qualitative analysis of trace impurities including C, H, Cl, and F in the samples. Based on the results of the qualitative analysis, quantitative analysis of trace impurities using AED showed that the highest mole fractions were for the $CHClF_2$ component ($45438.38{\mu}mol/mol$) in one sample and for the $C_2H_2ClF_3$ component ($1311.47{\mu}mol/mol$) in another sample. From this study, it has been shown that it is possible for this analytical method to be applied to the qualitative and quantitative analysis of trace compounds in refrigerants, which are difficult to quantify because of the absence of reference materials.

• Journal of the Korean Ceramic Society
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• v.13 no.2
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• pp.3-7
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• 1976

Influences of chlorides(CaCl2, MgCl2, NaCl) on the colouring effect of Fe component in white portland cement was investigated. Chlorides enhance the whiteness of the white portland cement owing to volatilization of Fe2O3 and translation of ferrite composition toward C2F. This translation is caused by consumption of alumina at the formation of C12A7, the formation of which is promoted in the presence of chloride. With decrease of p in ferrite composition C6F1-pAp, transfer of Fe3+ from 4 to 6 coordinated cite is occurred, and as a result, whiteness is raised. Hydration process of the cement containing a small amount of chloride differs little from the one without chloride.

• Journal of the Korean Chemical Society
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• v.18 no.6
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• pp.400-407
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• 1974

Steady-state anodic and cathodic polarization curves were developed for the Al electrode in 60 mole %$AlCl_3$-40 mole % NaCl at $180^{\circ}C$$453^{\circ}K$). Ohmic resistance contributed substantially to the anodic polarization at current densities greater than 50 mA/$CM^2$ even with capillary tip placed close to the electrode. This could not be rationalized from the resistivity of the melt, which would lead to a much smaller polarization. It was therefore concluded that a layer of high resistance $AlCl_3$ (or $AlCl_3$-rich melt) formed close to the anode surface. From the IR-corrected anodic Tafel and Allen-Hickling plots an apparent anodic charge-transfer coefficient of ${\alpha}_a$ = (2.3 RT/F)(d log i/d${\eta}$) = $1.5{\pm}0.25$ was obtained. At cathodic current densities greater than approximately 30 mA/$cm^2$, slow ion diffusion and dendrite growth both interfered with the measurement of kinetic parameters.

• Journal of the Korean Chemical Society
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• v.11 no.3
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• pp.94-99
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• 1967

The interactions of iodobenzene with iodine, iodine monobromide, iodine monochloride and chlorine in carbon tetrachloride solution have been investigated by means of ultraviolet spectrophotometric measurements. The results reveal the formation of one to one molecular complexes, $C_6H_5I{\cdot}I_2$, $C_6H_5I{\cdot}IBr$, $C_6H_5I{\cdot}ICl$, and $C_6H_5I{\cdot}Cl_2$, in solution. The equilibrium constants obtained at room temperature (about $21^{\circ}C$) for the formation of these four complexes are 0.23, 0.73, 1.2 and 0.070 l $mole^{-1}$, respectively. Comparison of these results with those reported in the literature on other complexes of similar type indicates that the relative stabilities of these complexes decrease in the following orders: ICl>IBr>$I_2$>$Br_2$>$Cl_2$ $C_6H_5I$>$C_6H_6$>$C_6H_5Br$>$C_6H_5Cl$>$C_6H_5F$.

• Journal of the Korean Chemical Society
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• v.44 no.2
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• pp.127-137
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• 2000

Eleven new compounds that are composed of bis(p-substituted phenyl) terephthalate unitand the decyloxy pendant as lateral were synthesized and their thermal and liquid crystalline properties were studied by the differential scanning calorimetry (DSC) and on a hot-stage of a polarizing microscope. The ter-minal substituent groups of the compound were varied; X= -H(II-H), -F(lI-F), -CII(II-CI), -Br(ll-Br), -I(II-I), -$NO_2(lI-NO_2$), $-CF_3(II-CF_3$), -$OC_2H_5(II-OC_2H_5$), -$OC_4H_9(II-OC_4H_9$), -$C_6H_5(Il-C_6H_5$). The compounds of $II-OC_2H_5,\;II-OC_4H_9$ and $II-C_6H_5$ were monotropically nematic. In contrast, the compounds of Il-H, II-F, II-Cl, II-Br, II-I, $lI-NO_2$, $II-CF_3$, and II-CN did not show liquid crystalline properties.

• Korean Journal of Soil Science and Fertilizer
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• v.14 no.3
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• pp.117-129
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• 1981

An experiment with the tobacco plant was conducted in the pots. A sandy humic soil was used with 2 levels of pH, 3.5 and 5.8 with 2 kinds of anions, Cl as $NH_4Cl$ and $SO_4$ as $(NH_4)_2SO_4$, and with 4 levels of pF, 1.5, 2.0, 2.5, and 3.5. The pH-treatment created different N-forms; $NH_4$ at low pH(3.5) and $NO_3$ at high pH (5.8). The results are summarized as follows: 1. At low pH (3.5) with high concentration of $NH_4$ given as $NH_4Cl$, the high content of $NH_4$ and Cl in tobacco resulted in plants suffering from $NH_4$ and Cl toxicity as well as Mn toxicity. As a result of these toxicity, an extremly abnormal growth of tobacco was clearly appeared. In the tobacco grown at low pH with $NH_4$ given as $(NH_4)_2SO_4$, a large amount of the $NH_4$ uptake developed Mg and Ca deficiencies. $NH_4-N$, which had been applied to the soil of high pH (5.8), was almost completely transformed into $NO_3-N$ by nitrification and, on this low acidic soil, the plants were all healthy regardless of Cl or $SO_4$ added together with $NH_4-N$. However, dry matter production was higher and maturity faster when $SO_4$ was used as anion than when Cl was used. 2. High moisture content in soil, to some extent, is necessary for a good development and growth of the tobacco plant. Phosphate uptake seemed to be limited at higher moisture stress. The dry matter yield of tops and roots of tobacco were in the order of pF 1.8 > 2.1 > 2.6 > 3.6, respectively. 3. Data of chemical analysis and dry matter yields of tops and roots showed that the tobacco plant followed the normal (C-A) concept. In the normal growth of plants, the carboxylate content of tops was quite comparable to the estimated (C-A) values. If $NH_4$ content of plants remains in quite high quantities, it must be analysed and taken into consideration for the (C-A) calculation. Al is not transported toward tops in toxic amounts due to its high immobility, it mostly stay in or on the roots, probably due to precipitation as a aolt. When Al is present in high quantities, it has to be considered into the (C-A) calculation.