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Effect of amine nature on reaction mechanism: Aminolyses of O-4-nitrophenyl thionobenzoate with primary and secondary amines

Title
Effect of amine nature on reaction mechanism: Aminolyses of O-4-nitrophenyl thionobenzoate with primary and secondary amines
Authors
Um I.-H.Lee S.-E.Kwon H.-J.
Ewha Authors
엄익환
SCOPUS Author ID
엄익환scopusscopus
Issue Date
2002
Journal Title
Journal of Organic Chemistry
ISSN
0022-3263JCR Link
Citation
vol. 67, no. 25, pp. 8999 - 9005
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
Pseudo-first-order rate constants (kobs) have been measured spectrophotometrically for reactions of O-4-nitrophenyl thionobenzoate (2) with a series of primary and acyclic secondary amines. The plots of kobs vs amine concentration are linear for the reaction of 2 with primary amines. The slope of the Brønsted-type plot for the reaction of 2 with primary amines decreases from 0.77 to 0.17 as the amine basicity increases, indicating that the reaction proceeds through a zwitterionic addition intermediate in which the rate-determining step changes from the breakdown of the intermediate to the reaction products to the formation of the intermediate as the amine basicity increases. On the other hand, for reactions with all the acyclic secondary amines studied, the plot of kobs vs amine concentration exhibits an upward curvature, suggesting that the reaction proceeds through two intermediates, e.g., a zwitterionic addition intermediate and an anionic intermediate. The microscopic rate constants (k1, k-1, k2, and k3 where available) have been determined for the reactions of 2 with all the primary and secondary amines studied. The k1 value is larger for the reaction with the primary amine than for the reaction with the isobasic acyclic secondary amines, while the k-1 value is much larger for the latter reaction than for the former reaction. The k3 value for the reaction with secondary amine is independent of the amine basicity. The small k2/k-1 ratio is proposed to be responsible for the deprotonation process observed in aminolyses of carbonyl or thiocarbonyl derivatives.
DOI
10.1021/jo0259360
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자연과학대학 > 화학·나노과학전공 > Journal papers
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