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ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 40, Number 2
JKCSEZ 40(2)
April 20, 1996 |
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Title |
A Study on the Kinetics and Mechanism of the Hydrolysis of Dihydro-1, 4-oxathiin Derivatives
Dihydro-1,4-oxathiin 유도체의 가수분해 Mechanism과 반응속도론적 연구 |
Author |
Kwang-Il Lee, Chun-Geun Kwak, Byung-Man Jang, Young-Ju Kim, Hoh-Gyu Hahn, Kee-Dal Naml, Ki-Chang Lee
이광일, 곽천근, 장병만, 김영주, 한호규, 남기달, 이기창 |
Keywords |
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Abstract |
Dihydro-1,4-oxathiin 유도체의 가수분해 반응속도를 25℃의 수용액에서 자외선 분광기를 사용하여 측정하고 넓은 pH 범위에서 적용될 수 있는 반응속도식을 유도하였다. 가수분해 반응속도에 미치는 치환기 효과를 검토하기 위하여 Hammett plot한 결과 전자 끄는기에 의하여 반응속도가 촉진됨을 확인할 수 있었다. 가수분해 최종 생성물은 2-(2-hydroxyethylthio)acetoacet-anilide enol형이었다. 가수분해 반응속도상수 측정실험과 반응속도식의 유도과정, 일반염기 효과, 치관기 효과 및 최종 생성물의 결과로부터 dihydro-1,4-oxathiin 유도체의 가수분해 반응 메카니즘을 제안하였다. pH 3.5 이하에서는 양성자가 첨가된 dihydro-1,4-oxathiin의 2번 탄소에 물분자의 공격에 의해 진행되며, pH 10.0 이상에서는 2번 탄소에 히드록시 이온의 첨가에 의하여 진행됨을 알 수 있었다. pH 4.0∼10.0 사이 에서는 dihydro-1,4-oxathiin에 중성의 물분자가 첨가되는 것이 속도결정단계임을 알았다. The kinetics of the hydrolysis of dihydro-1, 4-oxathiin derivatives were investigated by ultraviolet spectrophotometry in H2O at 25℃. A rate equation which can be applied over a wide pH range was obtained. The substituent effects on the hydrolysis of dihydro-1, 4-oxathiin derivatives were studied and the rate of hydrolysis was shown to be accelerated by electron accepting groups. Final product of the hydrolysis was 2-(2-hydroxyethylthio)acetoacet-anilide enol form. On the basis of rate equations derived and judging from hydrolysis products obtained and from general base effect and substituent effects, plausible mechanism of the hydrolysis in various pH range have been proposed. Below pH 3.5, the hydrolysis was initiated by the protonation and followed by the addition of water to 2-carbon. Above pH 10.0, the hydrolysis was proceeded by the addition of hydroxide to 2-carbon. In the range of pH 4.0∼10.0, the addition of water to dihydro-1,4-oxathiin is rate controlling step. |
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128 - 134 |
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