• Korean Chemical Engineering Research
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• v.45 no.4
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• pp.410-413
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• 2007

The effect of internal donor(ID) in the heterogeneous Ziegler-Natta catalyst on the ethylene-1-butene copolymerization and the molecular structure of the resulting copolymer was investigated. $SiO_2$-supported $TiCl_4$ catalysts having ID/Ti molar ratio of 0.5 were prepared with ethyaluminium dichloride, magnesium alkyl, 2-ethyl-1-hexanol and $TiCl_4$. Three different IDs were employed such as ethylbenzoate(EB), diisobuylphthalate(DIBP) and dioctylphthalate(DOP). ID-added catalyst showed a larger fraction of Ti(+3) compared to that of no ID-added catalyst. The EB-added catalyst showed the highest activity in copolymerization. Xylene soluble value decreased by more than 50 % with ID-added catalysts compared to that of no ID-added catalyst. Crystaf analysis showed the chemical compositional distribution of PE copolymer was improved in the case of DIBP-added catalyst significantly. It could be explained that the presence of ID could make more even active sites and block the non-stereospecific active sites.

• Journal of the Korean Chemical Society
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• v.36 no.3
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• pp.366-375
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• 1992

The aminolysis of carbamates are studied MO theoretically using AM1 method. The results indicated that the reactivity is determined by bond-making and-breaking and steric effects; as a result the $B_{AC}2$ mechanism is favored due to favorable contribution of bond formation in agreement with experimental results. We found that although thermal 2＋2 reaction is forbidden, it becomes allowed when the total electrons involved are six in a four-center reaction and proceeds by a consecutive onestep mechanism. Comparison of activation barriers show that greater energy is required in breaking a sigma bond compared with the energy required for breaking a $\pi$ bond, by 17 kcal/mol and the six membered ring structure is favored about 5 kcal/mol sterically.

• Applied Chemistry for Engineering
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• v.30 no.4
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• pp.509-511
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• 2019

Hydrazine derivatives used in fine chemicals, pharmaceuticals and cosmetics can be synthesized by reduction reaction from diazonium derivatives. The reduction method using $SnCl_2$ facilitates the reaction conversion, but the use of $SnCl_2$ is limited when residual heavy metals are issued in the final product. For the conversion of protected (2-hydroxyphenyl)diazonium derivatives into its hydrazine derivatives in Ramalin preparation process, the reduction method was developed by using $NaHSO_3$. In this study, the effect of steric hindrance according to the protected 2-hydroxygroupinphenyldiazonium derivatives was found, and linear C1~C5 alkyl groups for the hydroxy protection were preferable during the diazonium reduction reaction. Considering the economical efficiency and industrial production for the preparation of Ramalin, a variety of protecting groups were investigated. As a result, 2-(allyloxyphenyl)hydrazine was obtained with 85% yield and 99.7% purity when the hydroxy protecting group was used as an allyl group that could be easily deprotected.

• Journal of the Korean Chemical Society
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• v.24 no.5
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• pp.347-355
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• 1980

The rate constants for the reaction of ${\alpha}$-naphthalene carbonyl chloride and ${\beta}$-naphthalene carbonyl chloride have been determined in methanol-acetonitrile and methanol-acetone. The rate constant of ${\alpha}$-naphtalene carbonyl chloride is higher than that of ${\beta}$-naphthalene carbonyl chloride. This behavior is consistent with Dewar's number, Nr and also Streitwieser's value ${\sigma}^+$. Since in the transition state carbonyl carbon is transformed to$sp^3$, no peri-hydrogen effect was observed.

• Journal of the Korean Chemical Society
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• v.46 no.3
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• pp.229-232
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• 2002

Poly-o-toluidine (POT) was chemically and electrochemically synthesized for the study of electronic and steric effect of methyl substituents. The turn-on voltage of organic light emitting diode (OLED) was 9~14 V. ITO/POT/Al structured OLED were fabricated with various oxidation states of POT. PL, I-V characteristics and EL spectra were investigated.

• Proceedings of the Membrane Society of Korea Conference
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• 1996.10a
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• pp.49-50
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• 1996

비다공성막에서의 기체투과는 분리용막의 재료가 되는 기능성 고분자와 분리하고자 하는 기체 혼합물과의 작용이 투과확산을 지배하며 고분자의 구조에 의하여 결정되는 극성, 수소결합, 응집 에너지 밀도, 고분자 주쇄 유연성, 입체장애, 주쇄간 거리, 측쇄기의 운동성 등의 많은 인자들과 막결정화도 등의 인자들이 복합되어 기체투과에 작용하기 때문에 고분자 구조와 투과 특성과의 관계가 정량적으로 밝혀지지않고 있으나, 실험적 사실을 근거로 정성적 고찰이 이루어지고 있으며 몇가지 고분자막 미세구조를 나타내는 측정가능 물성들과 투과 특성을 상관시킬 수 있다. 폴리이미드막은 합성되는 diahydride와 diamine의 변화에 의해 다양한 화학적 구조를 갖는막을 만들 수 있으며 이들 막의 물성치들과 투과특성들도 서로 다르게 나타난다. 본 연구에서는 PMDA-MDA polyimide를 기본으로하여 다른 종류들의 Phenylene diamine을 첨가시켜 제조한 서로 다른 화학적 구조를 갖는 기체분리막들의 측정 가능한 물성치들과 산소, 질소 투과특성의 연관상을 연구하여 이들 사이의 정성적 상관성이 있음을 고찰한다.

• Journal of the Korean Chemical Society
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• v.54 no.6
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• pp.727-730
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• 2010

A tricyclic ring system bearing new stereogenic center namely 2,3-dihydro[1]benzothieno[3,2-b]pyrrole 4,4-dioxide was synthesized by asymmetric photoisomerization of 2,3-dihydropyrrolo[1,2-b]benzisothiazole 5,5-dioxide by irradiation with 245 nm emission of the low-pressure mercury lamp. The chemical structure and the purity of the photoproduct were delineated preliminarily by IR, NMR, and MS and finally confirmed by single crystal X-ray crystallography.

• Journal of the Korean Chemical Society
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• v.22 no.2
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• pp.55-61
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• 1978

MO theoretical studies on the conformations of N-acetylpyrrolidone and its protonated form were carried out by the EHT and CNDO/2 methods. According to our calculated results, the heavy atom skeleton of this molecule is planar, and the trans-trans planar conformation is more stable than cis-trans. The protonation occurs most readily on the ring carbonyl oxygen. These results were interpreted in terms of conjugative, electrostatic and steric effect.

• Journal of the Korean Chemical Society
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• v.25 no.1
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• pp.21-25
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• 1981

A study was made of the influence of butyl alcohol on the distribution coefficients of barium and mercury ions between the ion exchange resin, Dowex 50w-x8, 200~400 mesh and solutions containing hydrochloric acid, butyl alcohol and water. The determination of the distribution coefficients of barium and mercury are made by using the batch method. The distribution coefficients of metal ions decrease generally as the number of branches of carbon in the molecule of butyl alcohol increase. It shows that solubility in water and stereo-isomerism of the butyl alcohol have influence upon the distribution coefficient of barium and mercury.

• Journal of the Korean Chemical Society
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• v.22 no.4
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• pp.195-201
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• 1978

Configuration and conformation of nicotine and its protonated form have been studied by MO theoretically using EHT and CNDO/2 methods. The form with angle of rotation ${\theta}\;=\;280^{\circ}$ of pyrrolidine ring was shown to be most stable and this was interpreted in terms of conjugative, electrostatic and seric effects. It was predicted that protonation occurs on the nitrogen atom of pyridine ring and forms a ${\pi}$-complex.