• Polymer(Korea)
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• v.27 no.2
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• pp.129-134
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• 2003

It has been known that the intercalation of long alkyl chains in montmorillonites (MMT) increased the hydrophobicity as well as gallery spacing of UT, which has influenced on the exfoliation behavior of various polymers. A series of organophilic MMTs were synthesized from the water/isopropyl alcohol solution of MMT with ammonium salts of various alkyl amines. The properties of obtained MMTs such as thermal decomposition temperature, gallery spacing as well as hydrophobic property were investigated. The X-ray diffraction experiments on organophilic montmorillonite demonstrated that the increase of length of alkyl substituent resulted in increase in the spacing between silicate layers, which was ranged from 13.1 to 29.4 $\AA$. On the other hand, introduction of (di-, tri-) alkyl substituents in ammonium salts decreased water absorption of organophiplic montmorillonite to 2.7%.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4352-4360
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• 2011

A four dimensional quantitative structure activity relationship analysis was applied to a series of 50 flavonoid inhibitors of $p56^{lck}$ protein tyrosine kinase by the molecular comparative electron topological method. It was found that the -log (IC50) values of the compounds were highly dependent on the topology, size and electrostatic character of the substituents at seven positions of the flavonoid scaffold in this study. Depending on the negative or positive charge of the groups correctly embedded in these substituents, three-dimensional bio-structure to increase or decrease -log (IC50) values in the training set of 39 compounds was predicted. The test set of 11 compounds was used to evaluate the predictivity of the model. To generate 4D-QSAR model, the defined function groups and pharmacophore used as topological descriptors in the calculation of activity were of sufficient statistical quality ($R^2$ = 0.72 and $Q^2$ = 0.69). Ligand docking approach by using Dock 6.0. These compounds include many flavonoid analogs, They were docked onto human families of p56lck PTKs retrieved from the Protein Data Bank, 1lkl.pdb.

• Journal of Photoscience
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• v.6 no.4
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• pp.165-170
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• 1999

Asymmetric recognition of chiral alcohol by fluorenone derivatives with chiral substituents through intermolecular hydrogen bonding interaction in the singlet excited state was attempted. 1-((1S, 2R, 5S)-(+)-Menthyloxycarbonyl)aminofluoren-9-one (1-MAF) and 1-((1S, 2R, 5S)-(+)-menthyloxycarbonyl)oxyfluoren-9-one (1-MOF) were synthesized and their photophysical behaviors were characterized by the measurement of absorption and fluorescence spectra, as well as the quantum yield and the lifetime of fluorescence. The excited singlet states of 1-MAF and 1-MOF were revealed to have characteristics similar to those of fluorenone, though the intramolecular CT nature was fairly suppressed as compared with 3- and 4-substituted aminofluorenones. Fluorescences of 1-MAF and 1-MOF in acetonitrile were quenched by the addition of alcohols. Differences in fluorescence quenching efficiency were hardly observe for rather small chiral alcohols such as (R)-(-)- or (S)-(+)-2-butanol, while bulky alcohols such as menthol and isopinocampheol showed chiral recognition effects in their fluorescence quenching of 1-MAF in either acetonitrile or butyronitrile.

• Journal of the Korean Applied Science and Technology
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• v.14 no.1
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• pp.95-102
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• 1997

The synthetic method of pyrazole was performed by 1,3-dipolar cycloaddition with dipolarophile instead of the reaction between diazomethane and acetylene. The cycloaddition mechanism and reactivity of 3-phenyloxadiazole derivatives with dipolarophiles was investigated. In order to investigate the mechanism and reactivity of this cycloaddition, the effect of substituents having various kinds of electron withdrawing or releasing groups were examinated. Considering the effect of substituents, an electron withdrawing group attached at the 4-carbon position in 3-phenyloxadiazole derivatives decrease the reaction rate because of the lack of electron density in oxadiazole ring. The reaction rate of 3-phenyloxadiazole derivatives with dipolarophiles were more conveniently measured using UV than using a volumetric analysis which was used before. From the result of this study, it was that the cycloaddition was found to be a first-order reaction depending upon the concentration of 3-phenyloxadiazole only.

• YAKHAK HOEJI
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• v.55 no.2
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• pp.98-105
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• 2011

To search the minimum structural requirement of tricyclic isoxazole analogues (1~30) as new class potent antidepressant, thee-dimensional quanti- tative-structure relationship (3D-QSAR) models between substituents ($R_1{\sim}R_5$) of tricyclic isoxazoles and their antidepressant activity against medetomidine-induced loss of righting were performed and discussed quantitatively using comparative molecular field analysis (CoMFA) and comparative molecular similarity indies analysis (CoMSIA) methods. The correlativity and predictability ($r^2$=0.484 and $q^2$=0.947) of CoMSIA-2 model were higher than those of the rest models. The inhibitory activity against medetomidine-induced loss of righting was dependent on electrostatic field (43.4%), hydrophobic field (35.3%), and steric field (21.2%) of tricyclic isoxazoles. From the CoMSIA-2 contour maps, it is predicted that the antidepressant activity of potent antidepressants against medetomidine-induced loss of righting will be able to increase by the substituents ($R_1{\sim}R_5$) which were in accord with CoMSIA field.

• Bulletin of the Korean Chemical Society
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• v.30 no.10
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• pp.2233-2239
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• 2009

In the present study, firstly, the variations of the geometric parameters induced by different substituents on boroxine skeleton (symmetrically H, $CH_3$, Cl, F, $NO_2$ substituted boroxines) are investigated by using B3LYP/6-31G(d,p), RHF/6-31G(d,p), and MP2/6-31G(d,p) levels of the theory. The second objective is to estimate the substituent effect on the molecular aromaticity of boroxine derivatives using energetic and NICS criteria. Moreover, the effects of different theoretical levels on NICS values have been investigated in a systematic approach. Lastly, a rotational analysis has been performed to investigate the effect of rotation around the B-Me and B-$NO_2$ bonds on total energy of the system. It has been found that electron withdrawing substituents contribute the aromaticity of boroxine affirmatively. Conversely, electron donors make the system less aromatic. Also, the theoretical vibrational spectra for these boroxine derivatives are presented and compared with the experimental data from the literature.

• Bulletin of the Korean Chemical Society
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• v.23 no.4
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• pp.549-554
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• 2002

Thermosensitive poly(organophosphazenes) bearing methoxy-poly(ethylene glycol) (MPEG) and alkylamines as substituents have been synthesized and characterized by elemental analysis, NMR spectroscopy, GPC, and DSC. All the polymers exhibited crystallinity, which was probably induced by the MPEG side chain of the polymers. All the polymers exhibited the lower critical solution temperature (LCSTs) in the range of 28 to $94^{\circ}C$ depending on several factors such as mole ratio of the substituents, kinds of PEG and alkylamines. The higher content of MPEG and shorter chain length of alkylamines of the polymers afforded the higher LCST. The LCSTs of the polymers exhibited almost concentration-independent behavior in the range of 3-30 wt % of the polymers in aqueous solutions. The polymers showed the higher LCSTs in the acidic solutions than in the neutral and basic solutions. The ionic strength of the polymer solution affected the LCST, which decreased with increased NaCl concentration. The polymer bearing almost equimolar substitutuents with the -N-P-N- unit has shown the LCST more sensitive to NaCl and pH than that with the -N-P-O- unit. The polymers were found to degrade in acidic solution but be very stable in alkali solution as well as in the buffer solution of pH 7.4.

• Journal of the Korean Chemical Society
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• v.36 no.2
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• pp.180-184
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• 1992

Kinetic studies for the reaction of pyridine with substituted benzoyl chlorides were conducted under various pressures (1-1000 bar) in acetonitrile. From rate constants, the activation parameters (${\Delta}V^{\neq}$, ${\Delta}{\beta}^{\neq}$,${\Delta}H^{\neq}$, ${\Delta}S^{\neq}$ and ${\Delta}G^{\neq}$) were evaluated. Rates of these reaction increased with an increase in the pressure. The activation volume, the activation compressibility coefficient and the activation entropy were negative. From substituents effect and these results, it was found that these reactions proceed through $S_N2$ mechanism, but the structure of transition state was slightly changed with substituents and pressure.

• Bulletin of the Korean Chemical Society
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• v.28 no.9
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• pp.1567-1572
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• 2007

New pyrrolidinium and piperidinium bis(trifluoromethanesulfonyl)imide (TFSI) ionic liquids (ILs) having allyl substituents were synthesized and characterized. All of them are liquid at room temperature and stable up to 300 oC. The pyrrolidinium-based ILs showed better conductivities and lower viscosities than the corresponding piperidinium-based ILs. Among them, 1-allyl-1-methylpyrrolidinium TFSI showed the lowest viscosity of 52 cP, the highest conductivity of 5.7 mS cm?1, and the most negative cathodic voltage window of ?3.2 V (vs. Fc/Fc+) on a platinum electrode, which are the improved results compared to the corresponding analogue having a saturated substituent, 1-methyl-1-propylpyrrolidinium TFSI.

• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1108-1114
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• 2013

Photochemical reactions of fluoro- vs. nonfluoro-substituted polymethylenoxy chain linked phthalimide were carried out to explore how electronegative fluorine atoms inside the donor chain influence photocyclization reaction efficiencies and to briefly determine the alkali metal binding properties of the photoproducts. The results of this study show that the fluorine-substituted donor chain linked phthalimide undergoes inefficient photocyclization via single electron transfer (SET)-induced excited state pathways to generate 14-membered cyclic amidol compared to nonfluoro-analog due to low electron donor ability of the terminal oxygen donor site. These results show that photoinduced intramolecular SET processes arising from ${\alpha}$-silyl ether electron donors to phthalimides are largely dependent on the kinds of substituents inside donor chain. Finally, a preliminary study with the cyclic amidols generated in this effort showed that they have weak alkali metal cation binding properties regardless of absence/presence of fluoro-substituents.