Aminolysis of 3,4-Dinitrophenyl Cinnamate and Benzoate 2: Activation Parameters and Transition-State Structures

Bulletin of the Korean chemical society

Youn-Min Park¹  Ik-Hwan Um¹ 

关键词: Br©ªnsted-type plot;    Concerted mechanism;    Enthalpy of activation;    Entropy of activation;    Transitionstate;   

DOI  :  

学科分类：化学（综合）

来源: Korean Chemical Society

【 摘 要 】

The apparent second-order rate constants (k_N) have been dissected into the microscopic rate constants (i.e., k₁ and k₂/k_?1) associated with the reactions of Y-substituted phenyl cinnamates (5a-g) with piperidine and morpholine on the assumption that the reactions proceed through a stepwise mechanism with a change in the rate-determining step (RDS). The k₁ value is larger for the reactions with the more basic piperidine, and increases with decreasing the basicity of the leaving aryloxides. However, the k₂/k_?1 ratio is almost the same for the reaction of 3,4-dinitrophenyl cinnamate (5a) with piperidine and for that with morpholine, which is not possible if the reactions proceed through a stepwise mechanism. Thus, the aminolysis of 5a-g has been proposed to proceed through a concerted mechanism. The activation parameters (ツH�? and ツS�?) have been measured for the reactions of 3,4-dinitrophenyl benzoate (1a) and cinnamate (5a) with morpholine from the kinetic study performed at 5 different temperatures in 80 mol % H2O/20 mol % DMSO. The reaction of 5a results in a lager enthalpy of activation (ツH�?) but a less negative entropy of activation (ツS�?) than that of 1a.

【 授权许可】

Unknown