• Journal of the Korean Chemical Society
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• v.48 no.5
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• pp.461-466
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• 2004

Kinetics for the nucleophiles have been studied under high vacuum and high pressures in various temperatures. Pseudo-first order rate constants, second order rate constants, thermodynamic parameters and Hammett ${\rho}$-values are determined. The values of ${\Delta}V^{\neq},\;{\Delta}{\beta}^{\neq}\;and\;{\Delta}S^{\neq}$are all negative. The Hammett r-values are negative for the nucleophile (${\rho}$x) over the pressure range studied. The results of kinetic studies for pressure and nucleophilet show that these reactions proceed in typical $S_N2$ reaction mechanism and change of mechanism.

• Journal of the Korean Chemical Society
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• v.25 no.3
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• pp.145-151
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• 1981

The intrinsic reactivity of $S_N2$reaction in the gas phase was discussed MO theoretically (CNDO/2). We investigated the changes in geometry and electronic structure by means of the partial geometry optimization for reactantes, transition states, and products with various nucleophiles and leaving groups. We found that it was possible to discuss qualitatively the reactivity of $S_N2$ reaction with CNDO/2 MO calculation and the reactivity was controlled by basicity and of induced polarizability.

• Journal of the Korean Chemical Society
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• v.51 no.3
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• pp.244-250
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• 2007

A series of new 6-allylthio-3-aminopyridazine derivatives was synthesized through allylthiolation, amination and expected for anti-tumor activity. The pyridazine nucleus was obtained by condensing hydrazine monohydrate with maleic anhydride. 3,6-Dichloropyridazine was synthesized from 3,6-dihydroxypyridazine by treating with POCl3. 6-Allylthio-3-chloropyridazine was prepared from the reaction of 3,6-dichloropyridazine with allylmercaptan and sodium hydroxide. The heterocycles with nitrogen nucleophile such as morpholine, piperazine, pyrazole, imidazole, pyrrolidine, piperidine, perhydroazepine, and perhydroazocine were introduced into 3-position of pyridazine ring. The substitution reaction of 6-allylthio-3-chloropyridazine with heteroamines was performed by refluxing for 24~48 h in n-buthanol with NH4Cl.

• Journal of the Korean Chemical Society
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• v.20 no.6
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• pp.453-459
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• 1976

Rate constants for the reaction of methyl chloroformate with substituted anilines, and for the halogen exchanges in phenyl chloroformate have been determined in acetone. Although the rate data can be interpreted equally well with the addition-elimination mechanism($S_AN$) involving an intermediate, results of MO and isotope effect studies strongly favor the synchronous ($S_N2$) mechanism for the reactions studied. It was concluded that for the fast reacting nucleophiles the transition state is of "late" type while for the slow reacting nucleophiles it is of "early" type.

• Journal of the Korean Chemical Society
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• v.31 no.2
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• pp.123-132
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• 1987

Nucleophilic substitution reactions of methylthiocyanate(MTC) with anion nucleophiles,$SH^-,\;CN^-$ and $OH^-$, have been investigated using MNDO method. For the three reaction centers of MTC, gas-phase and solution-phase selectivities are discussed for each nucleophile by considering potential energy profiles calculated(intrinsic term) and magnitudes of negative charge on the nucleophile at the transition state(solvation term). It was found that both components of the selectivity for $SH^-$agreed with the experimental results obtained for 4-methylbenzylthiocyanate (4-MBTC), but the selectivity order for TEX>$CN^-$ was found to agree only with that of the intrinsic term and that of $OH^-$disagreed with any theoretical selectivity order. The MNDO optimized geometries for all species at the stationary points are reported.

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.40-47
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• 2015

본 연구에서는 일치환된 방향족 화합물의 $NO_2{^+}$ 치환반응에서의 반응성 (reactivity)과 지향성 (regioselectivity)에 대해 분석하였다. 기존의 연구에 따르면, 방향족 고리와 치환체 사이의 ${\sigma}$ 결합을 통한 유발효과와 ${\pi}$ 결합을 통한 공명효과로 인해 벤젠 고리의 전자 분포가 증가하게 되면 반응성이 증가하는 것으로 알려져 있다. 또한 반응중간생성물인 탄소양이온의 안정성을 통해 지향성을 확인할 수 있는 것으로 알려진 바가 있다. 이에 따라, 본 연구에서는 반응성과 지향성이 실험적으로 잘 알려진 7가지의 치환기 (OH, $OCH_3$, $CH_3$, Cl, COOH, CN, $NO_2$)를 선정하여 DFT functional인 B3LYP를 사용하여 natural bond orbital (NBO) 계산을 하였고, 각각의 일치환된 벤젠 고리가 갖는 전자 분포를 ${\sigma}$와 ${\pi}$ 전자로 나누어서 보기로 했다. 그 결과, 일치환된 방향족 고리 치환반응의 반응성과 지향성은 ${\sigma}$ 결합을 통한 유발효과에 의해서는 영향을 받지 않고, 공명 효과로 인한 반응물의 ${\pi}$ 전자 분포에 의해 결정되는 것을 확인할 수 있었다. 이외에도 반응성을 비교 하기 위해 친핵체로 작용하는 일치환된 방향족 고리의 highest occupied molecular orbital(HOMO) 에너지와 친전자체인 $NO_2{^+}$의 lowest unoccupied molecular orbital (LUMO) 에너지의 차이를 비교하였으며, 친핵체의 HOMO 에너지가 높을수록 반응성이 커짐을 알 수 있었다.

• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.562-567
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• 2007

The stereoselective synthesis of chiral terminal epoxide is of immense academic and industrial interest due to their use as versatile starting materials as well as chiral intermediates. In this study, new polymeric chiral Co(salen) complexes bearing tallium (III)chloride and iron (III)chloride (ferric chloride) have been synthesized and characterized. Their catalytic activity and selectivity have been demonstrated for the asymmetric ring opening of various terminal epoxides using water and phenol derivatives as nucleophiles. The easily prepared polymeric complexes exhibited very high enantioselectivity for the asymmetric ring opening of epoxides with $H_2O$ and phenol nucleophiles, providing enantiomerically enriched terminal epoxides (> 98% ee). The system described in this work is very efficient for the synthesis of chiral epoxide, 1,2-diol and ${\alpha}$-aryloxy alcohol intermediates.

• Journal of the Korean Chemical Society
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• v.40 no.8
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• pp.13-594
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• 1996

• Journal of the Korean Chemical Society
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• v.38 no.12
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• pp.908-914
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• 1994

6a-Hydroxy- and 6a-methoxy-derivatives (1∼6) of octahydro-2,3-dioxo-cyclopenta[b]-pyrrole-3a-carboxylate were synthesized from oxalylation of enamine A, which was prepared from condensation of five-membered cyclic ${\beta}$-keto ester and phenylalkylamine, followed by addition of water or methanol. The formation of heterocyclic ring was assumed to occur by the way of unstable N-acyliminium (B). Stable adduct C (1∼6) was obtained from nucleophilic addition to the endo-ene type pyrrolinium B.

• Journal of the Korean Chemical Society
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• v.29 no.5
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• pp.478-481
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• 1985

Nucleophilic substitution reactions between Alkanesulfonylchlorides and p-substituted anilines in methanol-acetonitrile mixture have been studied kinetically. Reactivities of substrates, substituent effects of nucleophile and solvent effects indicate that the studied reaction proceeds via $S_N2$. The kinetic results show that transition state of the reaction between i-PSC and anilines becomes looser as the composition of methanol increases.