Mechanism of the Hydrolysis of Phenyl N-(p-chlorobenzoyl)chloroformimidate Derivatives in Acid Media 


Vol. 31,  No. 4, pp. 352-358, Aug.  1987


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  Abstract

25℃의 1 : 4 dioxane-물의 혼합용액속에서 파라-치환된 phenyl N-(p-chlorobenzoyl)chloroformimidate (Ⅰ) 유도체들의 가수분해 반응속도 상수를 측정하고 반응속도식, 치환기 효과(ρ > ρ+), 생성물 분석 및 분자궤도 함수의 계산 결과로부터 pH3.0 이하에서는 azocarbonium 이온(Ⅱ)이 생성되는 SN1반응 메카니즘으로 무촉매 반응이 일어나며, pH 4.0이상에서는 전이상태(Ⅲ)를 지나는 SN2반응 메카니즘을 통하여 염기 촉매반응이 일어남을 제안 할 수 있었다. 4가지 peri planar형태 이성질체들의 상대적인 안정도는 각각 (E-ap) > (Z-ap) > (E-sp) > 및 (Z-ap)이었고, (E-ap)형태의 가장 안정한 입체구조는 benzimidochloroformyl group면에 대하여 Y-치환 phenyl group이 수직(90°)을 이루었으며 (Ⅰ)의 활성화된 azomethine탄소 원자에 대하여 물분자는 시그마 공격에 의하여 친핵성 반응이 일어난다. 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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  Cite this article

[IEEE Style]

N. Sung, Y. Cheun, K. Kwon, T. Kim, "Mechanism of the Hydrolysis of Phenyl N-(p-chlorobenzoyl)chloroformimidate Derivatives in Acid Media," Journal of the Korean Chemical Society, vol. 31, no. 4, pp. 352-358, 1987. DOI: .

[ACM Style]

Nack-Do Sung, Young-Gu Cheun, Ki-Sung Kwon, and Tae-Rin Kim. 1987. Mechanism of the Hydrolysis of Phenyl N-(p-chlorobenzoyl)chloroformimidate Derivatives in Acid Media. Journal of the Korean Chemical Society, 31, 4, (1987), 352-358. DOI: .

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ISSN(Print) 1017-2548
ISSN(Online) 2234-8530