• Journal of the Korean Applied Science and Technology
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• v.21 no.1
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• pp.24-30
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• 2004

New electroluminescent materials based on anthracene chromophore with naphthylethenyl substituent, 9,10-bis($\alpha$-naphthylethenyl)anthracene (a-BNA), as well as four kinds of its derivatives were synthesized, and luminescent properties of these materials were investigated. Electrolumineecent(EL) emission band was discussed based on their substituent structure differences. It was found that the emission band strongly depends on the molecular structure of introduced substituent. It can be tuned from 557 nm to 591 nm by changing the substituent structures. On the other hand, the anthracene chromophore with bulky substituent possessed high melting point and they gave stable films through vacuum-sublimation. The double layer EL device of ITO/TPD/emission layer/Mg:Ag was employed, and exhibited efficient orange light originating from emitting materials. EL emission with a maximum luminance was observed in the b-BNA emitting material, : maximum luminance was about 8,060 cd $m^{-2}$ at an applied voltage of 10 V and current density of 680 $mA/cm^2$. In conclusion, the electroluminescent properties also showed good difference with their substituent structure.

• Journal of the Korean Chemical Society
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• v.36 no.1
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• pp.38-43
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• 1992

The Hammett's substituent constants were interpreted for substituted stilbenes by HMO method. The appropriate quantum chemical indices are chosen as independent contribution of the inductive and the resonance effects for substituent constants. It has been found that theoretical values, ${\sigma}_p{^{th}}$, defined as sum of the net charge, self atom polarizability and difference in HOMO energy between substituted- and unsubstituted-stilbenes, correlated with experimental Hammett's substituent constants. The dipole moments were found to be correlated with differences in ${\sigma}_p{^{th}}$ between two substituents for disubstituted stilbenes. It has been also found that transition optical spectra, ${\lambda}_{max}$ of the substituted stilbenes depend on difference between the HOMO and the LUMO energy as expected.

• Journal of the Korean Applied Science and Technology
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• v.23 no.3
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• pp.177-184
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• 2006

Because of the difference in the relative reactivity between two hydroxyl groups of the hydroquinone due to the steric hindrance of the substituent, many combinations of the substituent direction in the polyesters derived from asymmetrical diphenol such as monosubstituted hydroquinone was expected. It was studied how the mode of the direction affected the properties of the resulting polyesters in terms of the transition temperatures of the thermotropic polyesters prepared from terephthalic acid, 2,4-dichloroterephthalic acid and phenylhydroquinone by the reaction using diphenyl chlorophosphate in pyridine. The direction was tried to control the relative reactivity by changing the reaction temperature and the addition time of hydroquinone, and by modifying it through an association of hydroquinone with LiCl.

• Journal of the Korean Society of Industry Convergence
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• v.5 no.2
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• pp.147-152
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• 2002

Because of the difference of the relative reactivity between two hydroxyl groups of the hydroquinone due to the steric hindrance of the substituent, many combinations of the substituent direction in the polyesters derived from asymmetrical diphenols such as monosubstituted hydroquinones was expected. It was studied how the mode of the direction affected the properties of the resulting polyesters in terms of the transition temperatures of the thermotropic polyesters prepared from terephthalic acid, 2,4-dichloroterephthalic acid, and phenylhydroquinone by the reaction using p-Toluenesulfonylchloride in pyridine. The direction was tried to control the relative reactivity by changing the reaction temperature and addition time of the hydroquinone, and by modifying it through an association of the hydroquinones with DMF.

• Journal of the Korean Chemical Society
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• v.20 no.5
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• pp.391-397
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• 1976

Substituent effects of leaving group in benzylarenesulfonates solvolysis have been carried out in 10∼50% water-acetone mixtures by electric conductivity method. Results of solvent effects, substituent effects and variable rate difference of water contents, show that $S_N1$ character almost predominates through the substituents, though p-MeO favors more or less $S_N2$ character in low water contents.

• Bulletin of the Korean Chemical Society
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• v.10 no.2
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• pp.151-154
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• 1989

4-Methoxy-4-methylcyclohexa-2,5-dienone 1 in aqueous sulfuric acid underwent the normal dienone-phenol rearrangement with methyl group migration. The fact that methyl is migrating group and methoxy is remaining group can be rationalized by the stabilization of positive charge at C-4 during the transition state. Methoxy methyl dienone 1 $((H_0)_{1/2} = - 4.6)$ is less basic than 4,4-dimethylcyclohexa-2,5-dienone whose half protonation acidity is reported as - 3.15 or - 3.66. This basicity difference comes from the unstabilization of the protonated methoxy methyl dienone 1 due to the electron withdrawing inductive effect of a methoxy group.

• Journal of the Korean Chemical Society
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• v.30 no.2
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• pp.172-180
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• 1986

The Hammett's substituent constants were analyzed for the substituted-benzoic acid, -benzene and -naphthalene by LCAO MO method. Hammett's ${\sigma}$-values have been theoretically proved to treat as the sum of independent contribution of inductive effect and resonance effect. That is, Is (static inductive effect) and Id (dynamic inductive effect) corresponding to inductive effect are chosen as net charge and approximate self atom polarizability indices respectively, and ${\Delta}E^{HOMO}$ which is the difference in HOMO energy level between substituted molecule and unsubstituted molecule as resonance effect. In conclusion, it has been found that the observed ${\sigma}$-values depend on the sum of Id, Is and ${\Delta}E^{HOMO}$.

• Bulletin of the Korean Chemical Society
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• v.29 no.4
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• pp.772-776
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• 2008

Second-order rate constants ($k_N$) have been measured spectrophotometrically for reactions of 3,4-dintrophenyl 2-furoate (2) with a series of secondary alicyclic amines in 80 mol % $H_2O$/20 mol % dimethyl sulfoxide (DMSO) at 25.0 ${^{\circ}C}$. The Bronsted-type plot exhibits a downward curvature for the aminolysis of 2, which is similar to that reported for the corresponding reactions of 2,4-dintrophenyl 2-furoate (1). Substrate 2 is less reactive than 1 toward all the amines studied but the reactivity difference becomes smaller as the amine basicity increases. Dissection of the second-order rate constants into the microscopic rate constants has revealed that the reaction of 2 results in a smaller $k_2/k_{-1}$ ratio but slightly larger $k_1$ value than that of 1. Steric hindrance has been suggested to be responsible for the smaller $k_1$ value found for the reactions of 1, since the ortho-substituent of 1 would inhibit the attack of amines (i.e., the $k_1$ process).

• Bulletin of the Korean Chemical Society
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• v.34 no.10
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• pp.2877-2882
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• 2013

Second-order rate constants ($k_{Ox^-}$) have been measured spectrophotometrically for nucleophilic substitution reactions of 4-nitrophenyl X-substituted-cinnamates (7a-7e) and Y-substituted-phenyl cinnamates (8a-8e) with butane-2,3-dione monoximate ($Ox^-$) in 80 mol % $H_2O$/20 mol % DMSO at $25.0{\pm}0.1^{\circ}C$. The Hammett plot for the reactions of 7a-7e consists of two intersecting straight lines while the Yukawa-Tsuno plot exhibits an excellent linearity with ${\rho}_X$=0.85 and r=0.58, indicating that the nonlinear Hammett plot is not due to a change in the rate-determining step but is caused by resonance stabilization of the ground state (GS) of the substrate possessing an electron-donating group (EDG). The Br${\o}$nsted-type plot for the reactions of Y-substituted-phenyl cinnamates (8a-8e) is linear with ${\beta}_{lg}$ = -0.64, which is typical of reactions reported previously to proceed through a concerted mechanism. The ${\alpha}$-nucleophile ($Ox^-$) is more reactive than the reference normal-nucleophile ($4-ClPhO^-$). The magnitude of the ${\alpha}$-effect (i.e., the $k_{Ox^-}/k_{4-ClPhO^-}$ ratio) is independent of the electronic nature of the substituent X in the nonleaving group but increases linearly as the substituent Y in the leaving group becomes a weaker electron-withdrawing group (EWG). It has been concluded that the difference in solvation energy between $Ox^-$ and $4-ClPhO^-$ (i.e., GS effect) is not solely responsible for the ${\alpha}$-effect but stabilization of transition state (TS) through a cyclic TS structure contributes also to the Y-dependent ${\alpha}$-effect trend (i.e., TS effect).

• Journal of the Korean Applied Science and Technology
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• v.37 no.2
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• pp.250-259
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• 2020

The solubilization constant (K_s) was determined by the UV-Vis method to investigate the interaction between organic matter (solubilized substance) and surfactant in solubilization. Solubilization constants and thermodynamic functions, according to the hydrophobic interaction between organic mater (4-alkylanilines with different alkyl substituent length) and cationic surfactants (DTAB, TTAB, and CTAB, having different hydrophobic lengths), were measured and calculated at various temperatures and compared with each other. As a result, the hydrophobic interactions between organic matters and cationic micelles increased with increasing the chain length of solute's substituent as well as surfactant's hydrophobe. However, the hydrophobic effect by the alkyl substituent of organic matter was greater than the hydrophobic effect by the surfactant. In addition, the results of the calculated thermodynamic functions showed that 4-alkylaniline was solubilized at the deep place in the micelle and its solubilization was greatly dependent on both the hydrophobic effects of organic matter and surfactant. At the calculated iso-structural temperature, the difference between the maximum and minimum values was less than 1K within the experimental conditions.