• 대한전자공학회논문지SD
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• 제43권2호
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• pp.13-17
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• 2006

Pentacene channel PTFT(organic thin film transistor)을 SiOC 절연박막 위에서 thermal evaporation 방법을 이용하여 성장시켰다. CVD 방법으로 증착시킨 SiOC 절연막은 조성비에 따라 특성이 달라지므로 절연막 위에서의 펜타센의 화학적 반응을 조사하기 위해서 inorganic-type인 $O_2/(BTMSM+O_2)=0.5$의 비율을 갖는 SiOC 박막을 사용하였다. 펜타센 분자의 말단에서 SiOC 표면에서 Diels-Alder 반응에 의한 이중결합이 깨어지면서 안정된 성장을 하지만 온도가 높아감에 따라 표면에서의 $SN_2(bimolecular nucleophilic substitution)$ 반응과 연쇄적인 화학반응에 의해 .펜타센의 성장을 방해하는 것으로 나타났다.

• Bulletin of the Korean Chemical Society
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• 제18권4호
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• pp.390-394
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• 1997

Nucleophilic substitution reactions of 2-thiopheneethyl benzenesulfonates (2-TEB) and 3-thiopheneethyl benzenesulfonates (3-TEB) with anilines and N,N-dimethylanilines (DMA) are investigated in acetonitrile at 60.0 ℃. The cross-interaction constants ρxz determined for the reactions with anilines are large negative (- 0.50) which are comparable to those for the similar predominantly frontside-attack SN2 reactions of 1-phenylethyl (1-PEB), 2-phenylethyl (2-PEB) and cumyl benzenesulfonates. A large negative ρxz value (- 0.4∼- 0.8) is considered to provide a mechanistic criterion for the frontside-attack SN2 mechanism with a four-center transition state. In agreement with this proposal the kinetic isotope effects, kH/kD, involving deuterated aniline nucleophiles are all greater than one reflecting partial N-H(D) bond cleavage in the transition state. The MO theoretical reactant structures of 1-PEB, 2-PEB and 2-TEB based on the PM3 calculation show that the benzene ring blocks the backside nucleophile approach to the reaction center carbon (Cα) enforcing the frontside-attack SN2 mechanism.

• 한국염색가공학회지
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• 제19권4호
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• pp.18-25
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• 2007

Kinetics and mechanism for alkaline hydrolysis of C. I. Disperse Green 9(G-9) of dinitrothiophene disperse dye were investigated. As soon as G-9 contacted with alkali, instant and continuous decreases of color strength of G-9 followed with increasing time. The hydrolysis rate of G-9 increased with increasing alkali, and it was found that alkali appeared first order dependence. The observed rate constants obtained from hydrolysis of various amount of dye were similar values, and calculation of initial rates showed that G-9 hydrolyzed by first order reaction for dye. Therefore it was confirmed that the overall reaction was second order, $SN_2$ of nucleophilic substitution reaction. Increasing temperature enhanced the hydrolysis of G-9. From the results of hydrolysis performed at various temperatures, it was obtained that activation energy(Ea) was 12.6 kcal/mole, enthalpy of reaction(${\triangle}H$) was 12.0 kcal/mole, and entropy of reaction(${\triangle}S$) was $29.8J/mol{\cdot}K$.

• Bulletin of the Korean Chemical Society
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• 제18권9호
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• pp.1010-1013
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• 1997

Nucleophilic substitution reactions of (Z)-phenylethyl (X)-benzenesulfonates with (Y)-pyridines were investigated in acetonitrile at 60 ℃ under respective pressures. The magnitudes of the Hammett reaction constants, ρX, ρY and ρZ indicate that a stronger nucleophile leads to a greater degree of bond formation of C-N and a better leaving group is accompanied by a less degree of bond breaking. The magnitude of correlation interaction term, ρij can be used to determine the structure of the transition state (TS) for the SN reaction. As the pressure is increased, the Hammett reaction constants, ρX and |ρY|, are decreased, but correlation interaction coefficient, ρXZ and |ρYZ|, are increased. The results indicate that the reaction of (Z)-phenylethyl (X)-benzenesulfonates with (Y)-pyridines probably moves from a dissociative SN2 to early-type concerted SN2 mechanism by increasing pressure. This result shows that the correlation interaction term ρij can be useful tool to determine the structure of TS, and also the sign of the product ρXZ·ρYZ can be predict the movement of the TS.

• 대한화학회지
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• 제41권1호
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• pp.22-46
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• 1997

25℃와 35℃에서 메탄올-아세토니트릴 혼합용매계에 대한 할로겐화 펜아실과 피리딘 치환체와의 친핵성치환반응을 속도론적으로 연구하였다. 전이상태 파라미터인 ΔH≠와 ΔS≠ 및 Brosted β값으로 보아 $S_N2$반응 메카니즘을 예상할 수 있었고, 이탈기 변화에 따른 QM모형의 적용으로 이들 반응의 전이상태 역시 생성물 닮은 구조임을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제18권8호
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• pp.868-873
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• 1997

Nucleophilic substitution reactions of 1-phenylethyl chlorides (1-PEC; YC6H4CH(CH3)Cl) with phenoxides (XC6H4O-) and thiophenoxides (XC6H4S-) are investigated theoretically using the PM3 method. The Bronsted α and β values are greater for the phenoxides indicating a more advanced reaction in the transition state (TS) than for the thiophenoxides. This is supported by a greater magnitude of ρX (- 6.4 ∼ - 7.4) and ρXY (- 0.76) for the phenoxides than for the thiophenoxides (ρX = - 3.6 ∼ - 4.4 and ρXY = - 0.60). The percentage bond order changes, %Δn≠, suggest that the extents of bond making and breaking are similar for the phenoxides and hence the TS is symmetrical, but bond making is somewhat greater than bond cleavage for the thiophenoxides indicating an unsymmetrical TS. The reactions in the gas phase for both nucleophile series proceed by a SN2 mechanism with a tight TS and negative charge development on the reaction center carbon, Cα. The reactions in water investigated with model systems of benzyl and 1-phenylethyl chlorides using the Cramer-Truhlar solvation model (PM3-SM3) indicate that the reactions of 1-PEC are far more complex due to enhanced stabilization of the carbocation by the methyl substitution for a benzylic hydrogen.

• 한국식품영양학회지
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• 제5권1호
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• pp.23-32
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• 1992

Kinetic studies of nucleophilic substitution reactions of dansyl, bansyl, dabsyl chlorides with pyridines have been investigated at $0^{\circ}C$ in a range of methanol-acetonitrile binary solvent mixtures. The order of magnitude for reactivity of substrates with pyridines in the same reaction condition is dabsyl chloride>dansyl chloride> bansyl chloride. The value of $\rho$n(-2.29~ -4.66) and $\beta$(0.537~0.901) associated with a change substituent in the nucleophile are large and indicate a relatively advanced bond formation in the transition state. Solvatochromic correlations were predicted the increase of bond formation transition state according to the increasing MeCN contents, showing the greater contribution of polarity polarizability ($\pi$*) than hydro-gen bond donar acidity($\alpha$). We conclude that the reactions of dansyl, bansyl, dabsyl chlorides with pyridines proceed via associative Sn2 type reaction mechanism.

• 대한화학회지
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• 제41권2호
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• pp.69-76
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• 1997

메탄올-아세토니트릴 혼합용매에서 벤조산 무수물의 아닐린에 의한 친핵성 치환반응을$35.0{\circ}C$에서 속도론적으로 연구하여 반응 메카니즘을 밝혔다. 벤조산 무수물에 있는 두 개의 카르보닐 탄소에서 경쟁적으로 치환반응이 일어나므로 반응 생성물의 비율로부터 각각의 반응속도$k_{XY}$와$k_{XZ}$를 구하였다. Hammett$p_i$값과 교차작용상수$p_{ij}$를 이용하여 전이상태구조 및 반응메카니즘을 규명하였다. 현저히 큰$p_X,\;p_{XY},\;p_{XZ}$및 양의값을 갖는$p_Y$의 크기로부터, 본 반응이 사각고리 전이상태를 갖는 전면공격$SN_2$메카니즘으로 진행됨을 알았다.

• 대한화학회지
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• 제18권3호
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• pp.175-179
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• 1974

Phenyl chloro-thiol, phenyl chloro-thiono 와 phenyl dithioformate에 분자궤도 함수론을 적용하여 계산 연구한 결과 모든 경우 trans형이 더 안정하며 또 SN반응기구는$ S_N2$형으로 일어날 가능성이 큼을 밝혔다

• 임산에너지
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• 제17권1호
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• pp.30-35
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• 1998

자유라디칼 반응기구에 의한 그라프팅 반응은 셀룰로오스의 낮은 반응 참여율, 반응의 저조한 반복성, 반응조절의 난이점, 특히 homopolymer의 높은 발생율로 인한 그라프팅 반응의 낮은 치환도 등의 문제를 지니고 있다. 이러한 문제를 해결하기 위하여 음이온중합 방법으로 polyacrylonitrile을 조제한 후 셀룰로오스 아세테이트와 균일계 반응조건에서 이분차 친핵치환(SN2) 반응기구에 의하여 그라프트 공증합 반응을 실시하였으며, 시간의 변화에 다른 겔의 형성과 그라프트 공중합 반응 전 후의 셀룰로오스 아세테이트의 FTIR spectra의 중요한 흡수대를 비교하여 반응을 확인하였다.