• Macromolecular Research
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• 제11권2호
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• pp.80-86
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• 2003

The polymerization of a cyclopolymerizable disubstituted dipropargyl ether, his(3-trimethylsilyl-2-propynyl)ether (BTPE), was attempted by various transition metal catalysts. The yield for the polymerization of BTPE was generally low, which is possibly due to the steric hindrance of bulky substituents. In general, the catalytic activities of Mo-based catalysts were found to be greater than those of W-based catalysts. The highest yield was obtained when the MoCl$_{5}$,-EtAlCl$_2$(1:2) catalyst system was used. The copolymerization of BTPE and diethyl dipropargylmalonate yielded a random copolymer with conjugated polymer backbone. However the polymers were partially desilylated, depending on the reaction conditions. The thermal and morphological properties of the resulting polymers were also discussed.d.

• 대한화학회지
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• 제44권5호
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• pp.470-476
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• 2000

이 연구에서는 비화학전공 공학계 학생들의 일반화학실험에 대한 흥미도를 조사하고, 이러한 흥미도에 영향을 미치는 요인이 무엇인지 분석하였다. 연구결과 학생들은 일반화학 실험주제에 따라 흥미도의 차이를 보여주었다. 학생들은 이론에 치우치고 이를 재확인하 는 실험보다는, 실행활과 관련이 있고 자신들이 직접 무엇인가를 만들어 내는 실험을 선호하였다. 이러한 학생들의 흥미도에 영향을 미치는 변인으로 실험을 담당한 조교, 학생들이 전공, 성별의 요소를 선정하여 분석하였다. 이 중 조교변인이 학생들의 흥미도에 가장 큰 영향을 미치는 것으로 나타났으며, 학생들의 전공이나 성별은 학생들의 흥미도에 큰 영향을 미치는 않는 것으로 나타났다.

• Bulletin of the Korean Chemical Society
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• 제28권1호
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• pp.89-94
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• 2007

The new pinane derivative containing unique multifused ring system was synthesized. The crystal, molecular and electronic structure of the title compound has been determined. Both pinane ring systems have the same conformation. The five-membered oxazolidine ring exists in twisted chair conformation. The structure is expanded through O-H…O hydrogen bond to semiinfinite hydrogen-bonded chain. The bond lengths and angles in the optimised structure are similar to the experimental ones. The CH3 and CH2 groups (except this of oxazolidine ring) are negatively charged whereas the CH groups are positively charged. The largest negative potential is on the oxygen atoms. The C-N natural bond orbitals are polarised towards the nitrogen atom (ca. 61% at N) whereas the C-O bond orbitals are polarised towards the oxygen atom (ca. 67% at O). It is consistent with the charges on the nitrogen and oxygen atom of oxazolidine ring and the direction of the dipole moment vector (3.08 Debye).

• EDISON SW 활용 경진대회 논문집
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• 제5회(2016년)
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• pp.147-154
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• 2016

Co-nonsolvency is a puzzling phenomenon that a polymer swells in a good solvent individually, but it collapses in a mixture of good solvents. This structural transition with changing solvent environment has been drawing attention due to practical application for stimuli-responsive polymer. The aim of this work is to describe the physical origin of the co-nonsolvency. In this work, we present Monte Carlo simulations for polymer solutions by using simple and general model. We simulate linear and ring polymers to compare their co-nonsolvency behaviors. Calculating Flory exponents and bridging fractions gives a good description for polymer structures. While the polymer structure shows non-monotonous behavior with increasing the cosolvent fraction, the chemical potential decreases monotonously. This indicates that coil-to-globule transition of polymers is purely controlled by free energy and can be regarded as a thermodynamics transition. We also present that ring polymers have higher looping probability than linear polymers, thus the bridging fraction remains higher at high cosolvent fraction. Our study provides a new perspective to understand polymer structure when the polymer "dissolves well" in any solvent.

• Nuclear Engineering and Technology
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• 제9권1호
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• pp.39-44
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• 1977

N-methyl-C-phenylalkyl ketimine 이성질체, Ph-CR=N$CH_3$ (R=H, $CH_3$, $CH_3$CH$_2$)의 배치와 형태를 EHT 분자궤도함수법으로 연구하였다. 계산결과는 C=N 이중결함에 대하여 E-형의 배치가 Z-형의 배치보다 안전함을 나타내고 있다. N-methyl-C-phenylaldimine과 N-methyl-C-phenylmethylketimine에서는 phenyl 고러 회전자가 C=N 평면과 동일평면에 있는 형태가 안정하다. N-methyl-C-phenylethylketimine에서는 phenyl 고리와 C=N결합이 동일평면에 있고 회전자 $CH_3$CH$_2$-가 C=N 평면과 90$^{\circ}$인 gauche형이 가장 안정하다.

• 한국결정학회지
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• 제16권2호
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• pp.81-88
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• 2005

결정내(結晶內)에 있는 원자(原子)들이 일반위치(一般位置)에 놓이면 그 원자(原子)들은 1-fald rotation symmetry를 갖는 열적(熱的)인 ellipsoid의 운동(運動)을 한다. 마찬가지로 special position에 놓인 원자(原子)는 special position의 대칭(對稱)에 맞는 열적운동(熱的運動)을 하여야 한다. 이 paper에서는 special position에 놓인 원자(原子)의 비등방성온도인자(非等方性溫度因子)의 계산방법(計算方法)을 보였다.

• Bulletin of the Korean Chemical Society
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• 제26권8호
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• pp.1241-1245
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• 2005

Solvolyses of trifluoromethanesulfonyl chloride (TFMSC) in water and in aqueous binary mixtures of acetone, ethanol and methanol are investigated at 25, 35 and 45 ${^{\circ}C}$. The Grunwald-Winstein plot of first-order rate constants for the solvolytic reaction of TFMSC with YCl (based on 2-adamantyl chloride) shows marked dispersions into three separate curves for three aqueous mixtures. The extended Grunwald-Winstein plots for the solvolysis of TFMSC show better correlation. The large negative ${\Delta}S^{\neq}$ and relatively small positive ${\Delta}H^{\neq}$ reveals that the solvolytic reaction proceeds via a typical bimolecular reaction mechanism. The l and m values determined in various solvents are consistent with the proposed mechanism of the general base catalysis $S_AN/S_N2$reaction mechanism for TFMSC solvolyses based on mass law and stoichiometric solvation effect studies.

• Bulletin of the Korean Chemical Society
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• 제33권3호
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• pp.775-778
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• 2012

The potential energy surfaces of ammonia molecule adsorptions on the symmetrically chlorinated Si(100)-$2{\times}1$ surface were explored with SIMOMM:MP2/6-31G(d). It was found that the initial nucleophilic attack by ammonia nitrogen to the surface Si forms a $S_N2$ type transition state, which eventually leads to an HCl molecular desorption. The second ammonia molecule adsorption requires much less reaction barrier, which can be rationalized by the surface cooperative effect. In general, it was shown that the surface Si-Cl bonds can be easily subjected to the substitution reactions by ammonia molecules yielding symmetric surface Si-$NH_2$ bonds, which can be a good initial template for subsequent surface chemical modifications. The ammonia adsorptions are in general more facile than the corresponding water adsorption, since ammonia is better nucleophile.

• Journal of Photoscience
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• 제10권1호
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• pp.1-7
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• 2003

The results of recent work on the dye-sensitized photooxygenation of sulfides is discussed. In the case of dialkyl sulfides, the weakly bonded adduct initially formed with singlet oxygen (the persulfoxide) decays unproductively unless protonation by an acid (an alcohol or a carboxylic acid) facilitates its conversion to the sulfoxide. The effect is proportional to the strength of the acid (eg., less than 0.1 % chloroacetic acid in benzene is sufficient for maximal efficiency) and corresponds to general acid catalysis, suggesting that protonation of the persulfoxide occurs. On the other hand, with sulfides possessing an activated hydrogen in ${\alpha}$ position (eg., benzyl and allyl sulfides), hydrogen transfer becomes an efficient process in aprotic media and yields a S-hydroperoxysulfoniumm ylide, possibly arising from a conformation of the persulfoxide that is different from the one protonated in the presence of acids. Calculations on some substituted sulfides support this hypothesis. This process, which leads to C-S bond fragmentation with formation of an aldehyde, may be viewed as a general method for the preparation of aryl and heteroaryl aldehydes. In this effort, mechanistic studies offered new hints on the structure of the intermediate persulfoxide.

• Applied Biological Chemistry
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• 제28권1호
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• pp.36-47
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• 1985

Saccharomyces cerevisiae의 HIS5 유전자는 세균 vector인 pBR 322와 shuttle vector pSH 610에 clone되었고 lactose operon의 promoter로서 발현되었다. HIS5-lac Z fusion은 효모의 제III번 염색체에 integration하였으며 HIS5 유전자는 general amino acid control을 받고 있었다.