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KMID : 1059519870310040352
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Journal of the Korean Chemical Society
1987 Volume.31 No. 4 p.352 ~ p.358
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Mechanism of the Hydrolysis of Phenyl N-(p-chlorobenzoyl)Chloroformimidate Derivatives in Acid Media
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Sung Nack-Do
Cheun Young-Gu
Kwon Ki-Sung
Kim Tae-Rin
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Abstract
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Rate constants for the hydrolysis of para-substituted phenyl N-(p-chlorobenzoyl)chloroformimidate (Ⅰ) derivatives in 1 : 4 dioxane-water at 25℃ have been determined. Rate data, substituent effect (ρ > ρ+), product analysis and MO calculation indicate that the uncatalyzed reaction proceeds through an SN1 mechanism involving the formation of azocarbonium ion (Ⅱ) below pH 3.0, and the base-catalyzed reaction proceeds through an SN2 mechanism via transition state (Ⅲ) above pH 4.0. The relative stability of four peri planar conformational isomers were (E-ap) > (Z-ap) > (E-sp) > (Z-ap), respectively, and the most stable stereo structures shows that the Y-substituted phenyl group (C6H4-Y) occupy vertical (90°) position on the plane of the benzimidochloroformyl group in (E-ap) conformer. The nucleophilic substitution of water molecule occurs by sigma attack to the activatived azomethine carbon atom of (Ⅰ) derivatives.
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