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KMID : 0903519950380050455
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Journal of the Korean Society of Agricultural Chemistry and Biotechnology
1995 Volume.38 No. 5 p.455 ~ p.462
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Kinetics and Hydrolysis Mechanism of Hervicidal N -(2,6 - dimethoxypyrimidin - 2 - yl) aminocarbonyl - 2 -(1 - hydroxy - 2 - fluoroethyl) benzenesulfonamide Derivatives
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Abstract
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The new six herbicidal N-[(pyrimidin-2-yl)aminocarbonyl]-2-substituted-6-(1-hydroxy-2-fluoroethyl)benzenesulfonamide derivatives(S) were synthesized and rate constants for the hydrolysis of their in the range of pH 1.0∼10.0 have been studied in 15%(v/v) aqueous acetonitrile solution at 45℃. From the basis of the results, pH-effect, solvent effect, ortho-substituent effect, thermodynamic parameters(△H^* & △S^*), pKa constant(4.80), rate equation, analysis of hydrolysis products(2-(1-hydroxy-2-fluoroethyl)benzenesulfonamide & 4,6-dimethoxyaminopyrimidine), it may be concluded that the general acid catalyzed hydrolysis through A-S_E2 mechanism and specific acid catalyzed hydrolysis through A-2 type(or A_(AC)2) mechanism proceeds via conjugate acid(SH^-) and tetrahedral intermediate(I) below pH 8.0, whereas, above pH 9.0, the general base catalyzed hydrolysis by water molecules(B) through (E₁)_(anion) mechanism proceeds via conjugate base(CB). In the range between pH 7.0∼pH 9.0, these two reactions occur competitively.
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KEYWORD
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