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Kinetic study on Michael-type reactions of 1-phenyl-2-propyn-1-one with alicyclic secondary amines: Effect of medium on reactivity and mechanism

Title
Kinetic study on Michael-type reactions of 1-phenyl-2-propyn-1-one with alicyclic secondary amines: Effect of medium on reactivity and mechanism
Authors
Hwang S.-J.Park Y.-M.Um I.-H.
Ewha Authors
엄익환
SCOPUS Author ID
엄익환scopusscopus
Issue Date
2008
Journal Title
Bulletin of the Korean Chemical Society
ISSN
0253-2964JCR Link
Citation
vol. 29, no. 10, pp. 1911 - 1914
Indexed
SCI; SCIE; SCOPUS; KCI WOS scopus
Abstract
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°C. 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 Brønsted-type plot is linear with βnuc = 0.40, which is slightly larger than that reported previously for the corresponding reactions in H2O (βnuc = 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 βnuc in the aprotic solvent. The nature of the transition state has been proposed to be responsible for the decreased reactivity in the aprotic solvent.
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자연과학대학 > 화학·나노과학전공 > Journal papers
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