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Modification of both the electrophilic center and substituents on the nonleaving group in pyridinolysis of O-4-nitrophenyl benzoate and thionobenzoates

Title
Modification of both the electrophilic center and substituents on the nonleaving group in pyridinolysis of O-4-nitrophenyl benzoate and thionobenzoates
Authors
Um I.-H.Hwang S.-J.Baek M.-H.Eun J.P.
Ewha Authors
엄익환
SCOPUS Author ID
엄익환scopusscopus
Issue Date
2006
Journal Title
Journal of Organic Chemistry
ISSN
0022-3263JCR Link
Citation
vol. 71, no. 24, pp. 9191 - 9197
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
(Chemical Equation Presented) A kinetic study is reported for reactions of 4-nitrophenyl benzoate (1c) and O-4-nitrophenyl X-substituted thionobenzoates (2a-e) with a series of pyridines in 80 mol % H2O/20 mol % dimethyl sulfoxide (DMSO) at 25.0 ± 0.1°C. O-4-Nitrophenyl thionobenzoate (2c) is more reactive than its oxygen analogue 1c toward all the pyridines studied. The Brønsted-type plot is linear with βnuc = 1.06 for reactions of 1c but curved for the corresponding reactions of 2c with βnuc decreasing from 1.38 to 0.38 as the pyridine basicity increases, indicating that the reaction mechanism is also influenced on changing the electrophilic center from C=O to C=S. The curvature center of the curved Brønsted-type plots (defined as pKao) occurs at pKa = 9.3 regardless of the electronic nature of the substituent X in the nonleaving group. The Hammett plot for reactions of 2a-e with 4-aminopyridine is nonlinear, i.e., the substrates having an electron-donating substituent exhibit negative deviations from the Hammett plot. However, the Yukawa-Tsuno plot for the same reactions exhibits good linear correlation, indicating that the negative deviations shown by these substrates arise from stabilization of the ground state through resonance interaction between the electron-donating substituent X and the C=S bond. © 2006 American Chemical Society.
DOI
10.1021/jo061682x
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자연과학대학 > 화학·나노과학전공 > Journal papers
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