Effect of Nonleaving Group on the Reaction Rate and Mechanism: Aminolyses of 4-Nitrophenyl Acetate, Benzoate and Phenyl Carbonate

Bulletin of the Korean chemical society

Ik-Hwan Um¹  Eun-Young Kim¹  Hye-Ran Park¹ 

关键词: Aminolysis;    Structure-reactivity relationship;    Rate-determining step;    Leaving group;   

DOI  :  

学科分类：化学（综合）

来源: Korean Chemical Society

【 摘 要 】

Second-order rate constants have been determined spectrophotometrically for the reaction of phenyl 4-nitrophenyl carbonate with a series of primary amines in H2O containing 20 mol % DMSO at 25.0 oC. The Br┆nsted-type plot is linear with a モnuc 0.69 �? 0.04, which is slightly smaller than the モnuc values for the reactions of 4-nitrophenyl acetate ( モnuc = 0.82 �? 0.03) and benzoate ( モnuc = 0.76 �? 0.01), indicating that the reaction proceeds through a tetrahedral zwitterionic intermediate T�?. The carbonate is more reactive than the corresponding acetate and benzoate. The changing Me (or Ph) to PhO has resulted in a decrease in the モnuc value without changing the reaction mechanism but an increase in the reactivity. The electronic effect of the substituent in the nonleaving group appears to be responsible for the enhanced reactivity of the carbonate compared with the corresponding acetate and benzoate.

【 授权许可】

Unknown