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Kinetic study on alkaline hydrolysis of Y-substituted phenyl X-substituted benzenesulfonates: Effects of changing nucleophile from azide to hydroxide ion on reactivity and transition-state structure

Title
Kinetic study on alkaline hydrolysis of Y-substituted phenyl X-substituted benzenesulfonates: Effects of changing nucleophile from azide to hydroxide ion on reactivity and transition-state structure
Authors
Moon J.-H.Kim M.-Y.Han S.-Y.Um I.-H.
Ewha Authors
엄익환한소엽
SCOPUS Author ID
엄익환scopusscopus; 한소엽scopus
Issue Date
2015
Journal Title
Bulletin of the Korean Chemical Society
ISSN
0253-2964JCR Link
Citation
vol. 36, no. 6, pp. 1563 - 1568
Keywords
Alkaline hydrolysisAryl benzenesulfonatesConcerted mechanismSulfonyl-group transferYukawa-Tsuno plot
Publisher
Korean Chemical Society
Indexed
SCI; SCIE; SCOPUS; KCI WOS scopus
Abstract
Second-order rate constants (k<inf>OH</inf>-) for alkaline hydrolysis of 2,4-dinitrophenyl X-substituted benzenesulfonates (1a-1f) and Y-substituted phenyl 4-nitrobezenesulfonates (2a-2g) have been measured spectrophotometrically. Comparison of k<inf>OH</inf>- with the k<inf>N3</inf>- values reported previously for the corresponding reactions with N<inf>3</inf>- has revealed that OH- is only 103 -fold more reactive than N<inf>3</inf>-, although the former is 11 pK<inf>a</inf> units more basic than the latter. The Yukawa-Tsuno plot for the reactions of 1a-1f results in an excellent linear correlation with ρ<inf>X</inf> = 2.09 and r = 0.41. The Brønsted-type plot for the reactions of 2a-2g is linear with β<inf>1g</inf> = -0.51, which is typical for reactions reported to proceed through a concerted mechanism. The Yukawa-Tsuno plot for the reactions of 2a-2g exhibits excellent linearity with ρ<inf>Y</inf> = 1.85 and r = 0.25, indicating that a partial negative charge develops on the O atom of the leaving group in the transition state. Thus, the alkaline hydrolysis of 1a-1f and 2a-2g has been concluded to proceed through a concerted mechanism. Comparison of the ρ<inf>X</inf> and β<inf>1g</inf> values for the reactions with OH- and N<inf>3</inf>- ions suggests that the reactions with hydroxide ion proceed through a tighter transition-state structure than those with azide ion. © 2015 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
DOI
10.1002/bkcs.10297
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자연과학대학 > 화학·나노과학전공 > Journal papers
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