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KMID : 1059519960400020128
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Journal of the Korean Chemical Society
1996 Volume.40 No. 2 p.128 ~ p.134
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A Study on the Kinetics and Mechanism of the Hydrolysis of Dihydro-1,4-oxathiin Derivatives
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Lee Kwang-Il
Kwak Chun-Geun
Kwak Chun-Geun
Kim Young-Ju
Hahn Hoh-Gyu
Nam Kee-Dal
Lee Ki-Chang
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Abstract
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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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