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Experimental and computational determination of Brønsted coefficients for equilibrium transfer of the O , O ‐dimethyl phosphorothioyl group between oxyanion nucleophiles
Author(s) -
Edwards David R.,
Maxwell Christopher I.,
Harkness Robert W.,
Neverov Alexei A.,
Mosey Nicholas J.,
Stan Brown R.
Publication year - 2012
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1903
Subject(s) - chemistry , nucleophile , oxyanion , methanol , leaving group , medicinal chemistry , group (periodic table) , bond cleavage , computational chemistry , stereochemistry , organic chemistry , catalysis
An experimental determination of the β Eq value for equilibrium transfer of the O,O ‐dimethyl phosphorothioyl group between oxyanion nucleophiles in water and methanol at 25 °C is presented. The respective β Eq values in the two solvents are experimentally the same at −1.45 ± 0.08 and −1.39 ± 0.12. Based on the observation that the Brønsted correlation for the nucleophilic reaction of phenoxides in water with substrate 1d (dimethyl 4‐nitrophenyl phosphorothioate, p K a HOAr of 7.14) is linear over the entire range of phenoxides employed (5.53 ≤ p K a Nu ≤ 12.38), the reaction for phenoxide nucleophiles displacing phenoxide leaving groups is probably concerted. The obtained data allow one to calculate, for a symmetrical transition state involving 2,4,5‐trichlorophenoxide as a nucleophile and leaving group, an approximately 60% P–OAr cleavage and about 40% P–Nuc bond formation. A computational method is presented for the rapid prediction of the β Eq values for such processes in water and methanol, and the results are compared with known values from the literature. Copyright © 2011 John Wiley & Sons, Ltd.