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Journal of the Korean Chemical Society (JKCS)

ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 38, Number 5
JKCSEZ 38(5)
October 20, 1994 

 
Title
A Study on the Kinetics and Mechanism of the Hydrolysis of 5,6-Dihydro-1,4-thiazine Derivatives

5,6-Dihydro-1,4-thiazine 유도체의 가수분해 메카니즘과 반응속도론적 연구
Author
Kwang-Il Lee, Suck-Woo Lee, Chun-Geun Kwak, Byung-Man Jang, Young-Ju Kim, Gi-Chang Lee

이광일, 이석우, 곽천근, 장병만, 김영주, 이기창
Keywords
Abstract
5,6-dihydro-1,4-thiazine 유도체의 가수분해 반응속도를 25℃의 수용액중에서 자외선 분광기를 사용하여 측정하고 넓은 pH범위에서 적용될 수 있는 반응속도식을 유도하였다. 가수분해 반응속도에 미치는 치환기 효과를 검토하기 위하여 Hammett plot한 결과 전자 주는기에 위하여 반응속도가 촉진됨을 확인할 수 있었다. 가수분해 최종생성물은 2-(N-acetylaminoethylthio)-acetoacetanilide enol형 이었으며 가수분해 반응속도상수 측정실험과 반응속도식의 유도과정, general base 효과, 활성화 파라미터 및 최종생성물의 결과로부터 5,6-dihydro-1,4-thiazine 유도체의 가수분해 반응은 pH 1.0∼10.0 에서는 중성의 물분자에 의해서 시작되며, pH 10.0∼11.0에서는 물분자와 히드록시 이온의 경쟁적인 반응이 pH11.0 이상에서는 히드록시이온에 의하여 진행됨을 알 수 있었다. 이러한 실험결과을 토대로 하여 5,6-dihydro-1,4-thiazine 유도체의 가수분해 반응메카니즘을 규명하였다.

The kinetics of the hydrolysis of 5,6-dihydro-1,4-thiazine derivatives was 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 5,6-dihydro-1,4-thiazine derivatives were studied and the rate of hydrolysis was shown to be accelerated by electron donating groups. Final product of the hydrolysis was 2-(N-acetylaminoethylthio)-acetoacetanilide enol from Judging from the results of the rate equation, general base effect, activation parameters and final products, the hydrolysis of 5,6-dihydro-1,4-thiazine derivatives seemed to be initiated by the neutral H2O molecule which does not dissociate at pH below 10.0, but proceeded by the hydroxide ion at pH above 11.0, and those two reactions occurred competively at pH 10.0∼11.0 range. On the basis of these findings a plausible mechanism for the hydrolysis of 5,6-dihydro-1,4-thiazine derivative was proposed.

Page
366 - 371
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