• 전기의세계
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• v.9
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• pp.28-35
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• 1962

많은 수의 동기기를 포함한 전력계통의 과도안정도를 계산함에 있어서 각각의 동기기를 독립적으로 취급하는 것은 실제상 불가능하며, 따라서 몇 대의 동기기를 1대의 동기기로 치환하여 계통을 간략하게 하는 것이 보통이다. 그러나 이렇게 함으로써 피시험동기기의 안정도에 주는 영향은 상금도 문제로 되어있다. 본 실험의 목적은 그 영향을 여러가지 운전조건에 대하여 검토하여 정당한 등치법을 찾는 데 있다.

• Journal of the Korean Chemical Society
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• v.31 no.5
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• pp.464-470
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• 1987

7-Substituted 2-aminophenazine-5,10-dioxides were synthesized by the reaction of 4-aminophenol with 6-substituted benzofuroxan derivatives which had been obtained from aniline derivatives bearing methoxy, methyl, acetyl, and nitro group at the para position. 2-Aminophenazine-5,10-dioxide was also prepared by the reaction of 4-aminophenol with benzofuroxan. The antimicrobial activities of these phenazine dioxide derivatives were investigated in terms of minimum inhibitory concentration by the common twofold dilution technique. It was observed that the antimicrobial activity of the phenazine dioxides bearing electron releasing substituents was stronger than that of those bearing electron withdrawing substituents. From this result, it was concluded that the antimicrobial activity of phenazine dioxide derivative has a direct relationship with the electronic effect of the substituents.

• Applied Biological Chemistry
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• v.41 no.1
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• pp.99-103
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• 1998

Triazolopyrimidine sulfonanilide (TP) derivative is one of excellent herbicide compounds. We have synthesized three classes of a new sulfonamide derivative (TPP) as Acetolactate synthase (ALS) inhibitors, in which the benzene ring in TP skeleton was converted to substituted pyrimidyl ring and examined their inhibitory activities on barley for ALS. $I_{50}$ values of the inhibitors ranged from 0.005 to 2 mM. Comparing the $I_{50}$ value of each class of TPP derivatives, the substituents in pyrimidine and triazolopyrimidine ring were found to affect the degree of ALS inhibition. TPP with substituted methyl group in pyrimidine ring showed higher inhibitory activity than that with methoxy group, while the substitution of the cyclopentano group in triazolopyrimidine ring gave very large inhibitory activity than that of methyl group. The present study established that variation of the electron density by substitution at heterocyclic ring is a very important factor for ALS inhibition, but showed no dependence on steric effect by substituents.

• Journal of the Korean Chemical Society
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• v.28 no.5
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• pp.279-283
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• 1984

${\beta}$-Substituent effect on the reactivity of retro-ene decarboxylation of but-3-enoic acid was investigated theoretically. It was found that charge effect is important not only through ${\pi}$-electron transfer as has been claimed to rationalize experimental results but also through polarization as found for the $CH_3$ substituent. The reactivity was not determined by the charge effect alone but the HOMO-LUMO energy gap was also found to affect the reactivity. In general it was confirmed that the greater the ${\pi}$-electron donating power of the substituent, the greater is the reactivity.

• Journal of the Korean Chemical Society
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• v.42 no.4
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• pp.391-397
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• 1998

The geometry of furan, relevant to the binding of bis-furan lexitropsin that contains this ring to the base pair of minor groove of DNA, is optimized by semiempirical (MNDO) and ab initio (Hartree-Fock) methods. The proton affinity and electronic structure are evaluated at the 6-31G and $6-31G^{\ast}$ level of theory for the optimized geometry. The proton affinities are also studied for various substituted furans with the electrondonating and -withdrawing groups to estimate the substituent effect on the proton affinity of furans. It has been found that the electron-donating substituents increase the proton affinity of furan, whereas the electron-withdrawing substituents decrease it. This result can be explained with atomic charge and electron density at oxygen of substituted furans.

• Journal of the Korean Chemical Society
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• v.32 no.2
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• pp.135-143
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• 1988

The correlations between chromatographic parameters of monosubstituted benzenes and several physical parameters in reversed phase liquid chromatography were studied. The relationships between retention data and polarity index were investigated by plotting $log(log k'_S/k'_B)$ vs. $P'_S/P'_B$ which were relative retention and relative polarity index of monosubstituted benzenes with respect to benzene, respectively. The linear relationship between relative retention and polarity index was observed for the monosubstituted benzenes having polar group, while in case of those having nonpolar group, the good linearity was observed by combination with relative molecular weight i.e. $(P'_S/P'_B)/(MW_S/MW_B)$. Multivariant regression analysis, $a(P'_S/P'_B)+b(MW_S/MW_B)$+c did not give significantly better correlations compared to single variant analysis, $a[(P'_S/P'_B)/(MW_S/MW_B)]$+c, but multiple stepwise regression analysis was recommended when several physical parameters simultaneously were chosen. The best correlation between retention data for monosubstituted benzenes taken from the literature and substituent constant(${\pi}$), derived from hydrophobic parameter and the first order molecular connectivity index$(^1{\chi}^{\nu})$, was established for methanol/water mobile phase system. The larger the surface coverage of the stationary phase, the higher was the correlation coefficient between these two parameters and retention data.

• Applied Biological Chemistry
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• v.42 no.1
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• pp.68-72
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• 1999

The cytotoxicity of 1,3-diphenylpropenone derivatives known to inhibit the farnesyl protein transferase (FPTase) was examined against various established tumor cell line, A549 (lung cancer), SKMEL-2 (uterine cancer), HCT-15 (skin cancer), SKOV-3 (brain cancer) and XF-498 (colon cancer) of the 1,3-diphenylpropenone derivatives showing farnesyl protein transferase (FPTase) inhibition activity. And the structure-activity relationship (SAR) between structure of 1,3-diphenylpropenone derivatives as substrate and cytotoxicity was investigated by Free-Wilson analysis as well as Hansch method with tumor cell lines. From the result of Free-Wilson analyses, X-substituents on the benzoyl group have a more important role than Y-substituents on the styryl group. The 2,4-dichloro substituent, 15 and 2,4-dimethyl substituent, 16 showed the highest cytotoxicity (average pI_(50)=5.0). Particulary, the cytotoxicity of X-substituents increased with electronic effect $({\sigma})$ due to weak electron withdrawing group with optimum value $({\sigma}_{opt}=0.22{\sim}0.29})$ whereas that of Y-substituent resulted from various factors such as logP, $B_1$ and R constant.

• Journal of the Korean Chemical Society
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• v.27 no.2
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• pp.133-141
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• 1983

The kinetics of the acid-catalyzed hydrolysis of a series of 1-aryl-2-pyrrylideneaniline (3) have been studied in 20% MeOH solution using UV spectrophotometer. Substituents in 3 showed a relatively small effect, with hydrolysis facilitated by electron withdrawing group. By obtaing linear plots of $log k_{obs}$ against Hammett ${\sigma}$ constants, it was able to show that substituents had a considerable contribution to the aromaticity of pyrrole compounds. The small positive ${\rho}$ values were consistent with the rate-determining addition of water to the protonated schiff base in the buffer solution of pH 4 to 8, whereas the addition of water to the free imine seemed to be the rate-determining in the solution of acidities greater than pH 8.

• Journal of the Korean Chemical Society
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• v.35 no.3
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• pp.196-203
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• 1991

The $pK_a$ values of benzoic acid and meta, para-halogen substituted benzoic acids in MeOH-$H_2O$ mixtures (0∼80% of MeOH) have been determined at 25$^{\circ}$C using a conductometric method on the basis of the Fuoss-Kraus equation, and further verified using modified conductometric method of Gelb. The dependence of $pK_a$ on halogen substituents has been discussed in terms of substituent-constant (${\sigma}$), which is devided into electron-withdrawing inductive contribution (${\sigma}_1$) and electron-donating ${\pi}$-resonance one (${\sigma}_R$). The linear-dependence of ${\sigma}_1$'s on $D^{-1}$ with positive slope and that of ${\sigma}_R$'s on $D^{-1}$ with negative slope have been interpreted on the basis of field effect and through-space interaction of ${\pi}$-lone pair of halogen substituent and ionization center via ${\pi}$-system of benzene ring.

• Korean Journal of Agricultural Science
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• v.28 no.1
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• pp.33-40
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• 2001

The authors attempted to derive a comprehensive quantitative structure-toxicity relationships (QSTRs) between various physicochemical parameters of phenyl substituents in fungicidal phenylthionocarbamate derivatives and toxicity evaluated using TOPKAT calculation. On the basis of this approach we made preditions for toxicity values for not yet tested substances with respect to these systems. The results suggested that the optimal values, $(B_2)_{opt.}=1.54_{\AA}$(Ames mutagenicity), $(R)_{opt.}=0.16$ (car-cinogenicity of male rat), $(\pi)_{opt.)=0.16$ (carcinogenicity of male mouse), $({\varepsilon}LOMO)_{opt}=-0.52e.v.$ ($LD_{50}$ of rat oral), $(B_3){opt.}=1.54_{\AA}$(chronic LOAEU), $(logP)_{opt.}=4.25$ ($LC_{50}$ of Fathead minnow) and $({\sigma})_{opt}=-0.68$ ($EC_{50}$ of Daphnia magna) of phenyl substituents were strongly correlated with the acute and chronic toxicities.