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Kinetics and reaction mechanism for aminolysis of benzyl 4-pyridyl carbonate in h2o: Effect of modification of nucleofuge from 2-pyridyloxide to 4-pyridyloxide on reactivity and reaction mechanism

Title
Kinetics and reaction mechanism for aminolysis of benzyl 4-pyridyl carbonate in h2o: Effect of modification of nucleofuge from 2-pyridyloxide to 4-pyridyloxide on reactivity and reaction mechanism
Authors
Kang J.-S.Um I.-H.
Ewha Authors
엄익환
SCOPUS Author ID
엄익환scopusscopus
Issue Date
2012
Journal Title
Bulletin of the Korean Chemical Society
ISSN
0253-2964JCR Link
Citation
vol. 33, no. 7, pp. 2269 - 2273
Indexed
SCI; SCIE; SCOPUS; KCI WOS scopus
Abstract
Pseudo-first-order rate constants kamine have been measured spectrophotometrically for the reactions of benzyl 4-pyridyl carbonate 6 with a series of alicyclic secondary amines in H 2O at 25.0°C. The plots of kamine vs. [amine] curve upward, indicating that the reactions proceed through a stepwise mechanism with two intermediates, a zwitterionic tetrahedral intermediate T ± and its deprotonated form T -. This contrasts to the report that the corresponding reactions of benzyl 2-pyridyl carbonate 5 proceed through a forced concerted pathway. The kamine values for the reactions of 6 have been dissected into the second-order rate constant Kk 2 and the thirdorder rate constant Kk 3. The Brønsted-type plots are linear with β nuc = 0.94 and 1.18 for Kk 2 and Kk 3, respectively. The Kk 2 for the reaction of 6 is smaller than the second-order rate constant kN for the corresponding reaction of 5, although 4-pyridyloxide in 6 is less basic and a better nucleofuge than 2-pyridyloxide in 5.
DOI
10.5012/bkcs.2012.33.7.2269
Appears in Collections:
자연과학대학 > 화학·나노과학전공 > Journal papers
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