• Bulletin of the Korean Chemical Society
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• v.27 no.1
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• pp.39-43
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• 2006

The relaxed torsional potential of a liquid crystalline polymer containing an ester functional group in a mesogenic unit (hereafter 12-4 oligomer) has been calculated with the ab initio self-consistent-field using 6-31G$^*$ basis set. GIAO^{13}C NMR chemical shifts also have been calculated at the B3LYP/6-31G$^*$ level of theory for each conformational structure obtained from torsional potential calculation. The results show that the phenyl ring-ester linkages are coplanar with the dihedral angle of about 0$^{\circ}$ and the ring-ring linkages in the biphenyl groups are tilted with the dihedral angle of around 43-44$^{\circ}$ in the lowest energy conformer. The biphenyl ring has a comparatively lower energy barrier of internal rotation potential in the ring-ring than that of phenyl ring-ester. The ^{13}C chemical shifts of carbonyl carbons were found to move to upfield due to $\pi$ -conjugation with phenyl ring and slightly affected about 0.5 ppm by dihedral angle of the ring-ring linkage.

• Bulletin of the Korean Chemical Society
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• v.18 no.9
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• pp.961-965
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• 1997

1H NMR spectra of 3,3-dimethylpiperidine (1) at -70 to 30 ℃ exhibit gradual change from slow to rapid exchange between two alternate chair forms. The exchange rate constant was determined as a function of temperature by simulating the line shape of the signal from the two methyl groups using the modified Bloch equations. The resulting free energy of activation is ΔG* = 44.4±1.9 kJ mol-1 at 298 K. The 1H NMR spectrum of a D2O or dimethylsulfoxide-d6 (DMSO-d6) solution containing 1 and [SiW11CoⅡO39]6- exhibits separate signals for the free ligand and the complex, indicating that the ligand exchange is slow on the NMR time scale. In D2O the piperidine ring is frozen as a chair form even at room temperature with the cobalt ion bonded to the axial position of the nitrogen atom. When DMSO-d6 is added to the D2O solution, the NMR spectral change suggests that a rapid exchange occurs between the chair form and another conformer. It is proposed that the conformation of ^b1^b coordinated to [SiW11CoⅡO39]6- in DMSO-d6 is close to a twist form.

• Journal of the Korean Chemical Society
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• v.31 no.4
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• pp.352-358
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• 1987

Rate constants for the hydrolysis of para-substituted phenyl N-(p-chlorobenzoyl)chloroformimidate (I) derivatives in 1 : 4 dioxane-water at $25^{\circ}C$ have been determined. Rate data, substituent effect $(\rho\>{\rho}^+)$, product analysis and MO calculation indicate that the uncatalyzed reaction proceeds through an $S_N1$ mechanism involving the formation of azocarbonium ion (II) below pH 3.0, and the base-catalyzed reaction proceeds through an $S_N2$ mechanism via transition state (III) above pH 4.0. The relative stability of four peri planar conformational isomers were (E-ap) > (Z-ap) > (E-sp) > (Z-ap), respectively, and the most stable stereo structures shows that the Y-substituted phenyl group $(C_6H_4-Y)$ occupy vertical $(90^{\circ})$ position on the plane of the benzimidochloroformyl group in (E-ap) conformer. The nucleophilic substitution of water molecule occurs by sigma attack to the activatived azomethine carbon atom of (I) derivatives.

• Journal of Korean Ophthalmic Optics Society
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• v.7 no.2
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• pp.95-99
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• 2002

To investigate the manual procedure for custom fitting of ocular prosthesis and the cytotoxicity induced by extract solution of prosthetic eye, this study was performed. These procedures included the trial fitting of the wax model, impression molding, the an of iris color duplication, sclera mold made from the prosthetic wax model, scleral tints and vascular pattern, finishing and polishing. Inhibition of cell growth for extract solution was measured by MTT assay. Extract solution did not show the cytotoxicity. This study suggests that the manual procedure for custom fitting of ocular prosthesis is good for education of students.

• Applied Biological Chemistry
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• v.37 no.4
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• pp.287-294
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• 1994

New 3-phenyl-1-(2-furyl)propenones, 1 and 3-phenyl-1-(2-furyl)-3-thiophenyl-propanone, 2 derivatives were synthesized, and their fungicidal activities in vitro against Botrytis cineria (BC), Valsa ceratosperma (VC), Scelerotium cepivorum (SC) and Phytophthora capsici (PC) were investigated using a generalized structure-activity relationship (SAR). The activity of 1 was superior to those of 2, and nonsubstituent, 1a and chloro group substituent, 1d of E (Syn) conformer were the most effective $(EC_{50}=10{\sim}12\;ppm)$ compound to BC. Antifungal activities were able to predict to depend essentially on the ${\beta}$ carbon and their positive charge from the results that the good correlation $(r^2=0.90)$ was observed between hydrolysis rate constant (logk) of 1 and the electronic parameter $({\sigma})$ of X-substituent on the ${\beta}-phenyl$ ring.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2311-2316
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• 2014

Conformations and vibrational frequencies of the racemic (2RS,3RS)-5-amino-3-(4-phenylpiperazin-1-yl)-1,2,3,4-tetrahydronaphthalen-2-ol-(I) [(2RS,3RS)-(I)], a precursor of benzovesamicol analogues, have been carried out using various DFT methods (M06-2X, B3LYP, B3PW91, PBEPBE, LSDA, and B3P86) with basis sets of 6-31G(d), 6-31+G(d,p), 6-311+G(d,p), 6-311++G(d,p), cc-pVTZ, and TZVP. The LSDA/6-31G(d) level of theory shows the best performance in reproducing the X-ray powder structure. However, the PBEPBE/cc-pVTZ level of theory is the best method to predict the vibrational frequencies of (2RS,3RS)-(I). The potential energy surfaces of racemic pairs (2RS,3RS)-(I) and -(II) are obtained at the LSDA/6-31G(d) level of theory in the gas phase and in water. The results indicate that (2RS,3RS)-(I) are more stable by ~0.75 kcal/mol in energy than (2RS,3RS)-(II) in water, whereas conformer AIIg and BIIg are more stable by ~0.04 kcal/mol than AIg in gas phase. In particular, the hydrogen bond distances between the N of piperazine and the OH of tetrahydronaphthalen become longer in gas, compared with those in the water phase. Vibrational frequencies calculated at the PBEPBE/cc-pVTZ level of theory in the gas phase are larger than those in water, whereas their intensities in the gas phase are weaker than those in water.

• Korean Journal of Agricultural Science
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• v.22 no.2
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• pp.127-133
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• 1995

A Series of meta and para-substituted phenyl N-methylcarbamate derivatives were synthesized and influence of substituents(X) on the molecular orbital(MO) quantities of carbonyl group, carbamylation reaction center, and insecticidal activities($pI_50$) were discussed quantitatively. From these findings, the most stable streo conformer(Z) shows that the planer phenyl group occupies vertical(${\theta}=90^{\circ}$) position on the plane of the N-methylcarbamyl group. The carbamylation mechanism was proposed that the carbamylation process of acetylcholinesterase(ACh.E) by m-methyl substituted phenyl N-methylcarbamate derivatives proceeds via hyperconjugation of m-methyl group and carbonyl oxygene protonation, theromodynamically control reaction with acidic site of ACh.E.

• Bulletin of the Korean Chemical Society
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• v.27 no.4
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• pp.508-514
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• 2006

In this study, we have performed ab initio computer simulations to investigate the conformational and complexation characteristics of the trimethyl ether of p-tert-butylmonodeoxycalix[4]arene (6) with a potassium ion. The structures of different conformers of 6 and their potassium complexes were optimized by using ab initio RHF/6-31G and B3LYP/6-31G(d,p) methods. The relative stability of the various conformers of the uncomplexed 6 is in following order: cone (most stable) > 1-partial-cone ~ 2i-partial-cone > 2-partial-cone ~ 1,3-alternate > 3i-partial-cone. However, the relative stability of the conformational complexes of 6 with $K^+$ is in the following order: 2-partial cone ~ 1,3-alternate > cone > 3-partial cone > 1-partial cone (least stable). The highest binding strengths of 2-partial-cone and 1,3-alternate complexes originate from two strong cation-$\pi$ interactions and two strong cation-oxygen interactions in the complex of 6+$K^+$. Due to the cation-$\pi$ interactions, the calculated C-C bond distances in the arenes of the $K^+$-complexes are about 0.0048 $\AA$ longer than the values of their isolated hosts.

• Bulletin of the Korean Chemical Society
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• v.32 no.3
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• pp.793-799
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• 2011

We report the complexation behavior of calix[4]arenemonoquinone-triacid (CTAQ), which is an electroactive and water-soluble receptor for calcium ion. UV-visible and NMR spectroscopic studies revealed that CTAQ in aqueous media forms 1:2 as well as 1:1 (metal ion:CTAQ) stoichiometric complexes with $Ca^{2+}$, $Sr^{2+}$, and $Ba^{2+}$ ions. The nonlinear fitting of titration curves based on UV-visible absorption spectra showed that the binding constants of CTAQ for $Ca^{2+}$ ion are 4 $({\pm}2){\times}10^6\;M^{-1}$ for 1:1 and 1.4 $({\pm}0.5){\times}10^{11}\;M^{-2}$ for 1:2 complex. NMR conformational studies and the titration curves corroborate that the $Ca^{2+}$:CTAQ complex in aqueous solution is not present in the form of merely 1:1 one, being consistent with UV-visible spectrophotometric results. The Monte Carlo simulation supports the presence of a stable conformer of 1:2 complexes in which a $Ca^{2+}$ ion is interposed between two CTAQs at the global minimum. This is the first model of 1:2 stoichiometric complex of calix[4]arene and alkaline earth ions in aqueous media.

• Journal of the Korean Chemical Society
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• v.40 no.7
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• pp.483-491
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• 1996

Dieis-Alder reaction between cyclopentadiene and 5-membered ring compounds which have exo-cyclic double bond has been studied using the PM3 method. Transition states do not show large geometrical change with the variation of dienophiles. Two isomers are possible due to the rotation of the exo-cyclic double bond of a dienophile. The reactivity for the formation of different products are explained using the FMO energy gap. The exo and endo selectivity of the reaction has been also studied from the correlation between the deformation energy and the activation barrier. Minimum energy reaction path is discussed using the Curtin-Hammett principle.