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Effect of acyl substituents on the reaction mechanism for aminolyses of 4-nitrophenyl X-substituted benzoates

Title
Effect of acyl substituents on the reaction mechanism for aminolyses of 4-nitrophenyl X-substituted benzoates
Authors
Um I.-H.Min J.-S.Ahn J.-A.Hahn H.-J.
Ewha Authors
엄익환
SCOPUS Author ID
엄익환scopusscopus
Issue Date
2000
Journal Title
Journal of Organic Chemistry
ISSN
0022-3263JCR Link
Citation
vol. 65, no. 18, pp. 5659 - 5663
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
Second-order rate constants (k(N)) have been measured spectrophotometrically for the reaction of 4-nitrophenyl X-substituted benzoates with a series of alicyclic secondary amines in H 2O containing 20 mol % dimethyl sulfoxide at 25.0 °C. The magnitude of the k(N) values increases with increasing the basicity of amines and with increasing the electron-withdrawing ability of the acyl substituent X. The Hammett plots obtained are not linear but show a break or curvature as the acyl substituent X becomes electron withdrawing for all the amines studied, while the Bronsted-type plots are linear with large β(nuc) values for all the substrates investigated. The nonlinear Hammett plots suggest a change in the rate-determining step upon changing the acyl substituent X, whereas the linear Bronsted-type plots indicate that the rate-determining step does not change upon changing amine basicity. The Yukawa-Tsuno plots obtained are also linear with positive ρx and large r values, suggesting that the nonlinear Hammett plots are not due to a change in the rate-determining step upon changing the acyl substituent X, but due to resonance demand of the π-electron donor substituent on the acyl moiety. The magnitude of the ρx and β(nuc) values increases with increasing the basicity of amines and with increasing the electron-withdrawing ability of the acyl substituent X, respectively, while that of the r values decreases with increasing ρx values and amine basicity.
DOI
10.1021/jo000482x
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자연과학대학 > 화학·나노과학전공 > Journal papers
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