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Nucleophilic substitution reactions of diethyl 4‐nitrophenyl phosphate triester: Kinetics and mechanism
Author(s) -
Castro Enrique A.,
Ugarte Daniela,
Rojas M. Fernanda,
Pavez Paulina,
Santos José G.
Publication year - 2011
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.20605
Subject(s) - chemistry , nucleophile , alicyclic compound , aminolysis , nucleophilic substitution , concerted reaction , kinetics , reaction rate constant , medicinal chemistry , leaving group , reaction mechanism , computational chemistry , catalysis , organic chemistry , physics , quantum mechanics
The reactions of diethyl 4‐nitrophenyl phosphate ( 1 ) with a series of nucleophiles: phenoxides, secondary alicyclic (SA) amines, and pyridines are subjected to a kinetic study. Under excess of nucleophile, all the reactions obey pseudo‐first‐order kinetics and are first order in the nucleophile. The nucleophilic rate constants ( k N ) obtained are pH independent for all the reactions studied. The Brønsted‐type plot (log k N vs. p K a nucleophile) obtained for the phenolysis is linear with slope β=0.21; no break was found at p K a 7.5, consistent with a concerted mechanism. The Brønsted‐type plots for the SA aminolysis and pyridinolysis are linear with slopes β=0.39 and 0.43, respectively, also suggesting concerted processes. The concerted mechanisms for the latter reactions are proposed on the basis of the lack of break in the Brønsted‐type plots and the instability of the hypothetical pentacoordinate intermediates formed in these reactions. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 708–714, 2011