Bulletin of the Korean chemical society | |
Aminolysis of 3,4-Dinitrophenyl Cinnamate and Benzoate 2: Activation Parameters and Transition-State Structures | |
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 (kN) 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
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