Bulletin of the Korean chemical society | |
Kinetic Study on Michael-type Reactions of 1-Phenyl-2-propyn-1-one with Alicyclic Secondary Amines: Effect of Medium on Reactivity and Mechanism | |
Ik Hwan Um1  Youn Min Park1  So Jeong Hwang1  | |
关键词: Michael-type reaction; Concerted mechanism; Stepwise mechanism; Br©ªnsted-type plot; Medium effect; | |
DOI : | |
学科分类:化学(综合) | |
来源: Korean Chemical Society | |
【 摘 要 】
Second-order rate constants (kN) have been measured for Michael-type addition reactions of a series of alicyclic secondary amines to 1-phenyl-2-propyn-1-one (2) in MeCN at 25.0 �? 0.1 oC. All the amines studied are less reactive in MeCN than in H2O although they are more basic in the aprotic solvent by 7-9 pKa units. The Br┆nsted-type plot is linear with �?nuc = 0.40, which is slightly larger than that reported previously for the corresponding reactions in H2O (�?nuc = 0.27). Product analysis has shown that only E-isomer is produced. Kinetic isotope effect is absent for the reactions of 2 with morpholine and deuterated morpholine (i.e., kH/kD = 1.0). Thus, the reaction has been concluded to proceed through a stepwise mechanism, in which proton transfer occurs after the rate-determining step. The reaction has been suggested to proceed through a tighter transition state in MeCN than in H2O on the basis of the larger �?nuc in the aprotic solvent. The nature of the transition state has been proposed to be responsible for the decreased reactivity in the aprotic solvent.
【 授权许可】
Unknown
【 预 览 】
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RO201912010240725ZK.pdf | 283KB | download |