期刊
JOURNAL OF ORGANIC CHEMISTRY
卷 77, 期 13, 页码 5781-5787出版社
AMER CHEMICAL SOC
DOI: 10.1021/jo300961y
关键词
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资金
- Basic Science Research Program through the National Research Foundation of Korea (NRF)
- Ministry of Education, Science and Technology [2009-0075488]
- BK 21 Scholarship
A kinetic study is reported for aminolysis of 4-pyridyl X-substituted-benzoates 5a-i. Plots of pseudo-first-order rate constants (k(obsd)) vs [amine] curve upward for the reactions of substrates possessing a strong electron-withdrawing group in the benzoyl moiety (5a-d) but are linear for the reactions of those bearing an electron-donating group (5e-i), indicating that the electronic nature of substituent X governs the reaction mechanism. The k(1)k(2)/k(-1) and k(1)k(3)/k(-1) values were calculated from the intercept and slope of the linear plots of k(obsd)/[amine] vs [amine], respectively. The Hammett plot for k(1)k(2)/k(-1) consists of two intersecting straight lines, while the Yukawa-Tsuno plot exhibits an excellent linear correlation with rho(x) = 0.41 and r = 1.58, implying that the nonlinear Hammett plot is not due to a change in rate-determining step but is caused by stabilization of substrates possessing an electron-donating group through resonance interactions. The small rho(x) suggests that the k(2)/k(-1) ratio is little influenced by the nature of substituent X. The Bronsted-type plots for aminolysis of 4-pyridyl 3,5-dinitrobenzoate 5a are linear with beta(nuc) = 0.98 and 0.79 for k(1)k(2)/k(-1) and k(1)k(3)/k(-1), respectively. The effect of amine basicity on the microscopic rate constants is also discussed.
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