96461-36-8Relevant articles and documents
Anilinolysis of reactive aryl 2,4-dinitrophenyl carbonates: Kinetics and mechanism
Castro, Enrique A.,Domecq, Claudia,Santos, Jose G.
, p. 191 - 197 (2011)
The reactions of a series of anilines with phenyl 2,4-dinitrophenyl (1), 4-nitrophenyl 2,4-dinitrophenyl (2), and bis(2,4-dinitrophenyl) (3) carbonates are subjected to a kinetic investigation in 44 wt% ethanol-water, at 25.0 ± 0.1°C and an ionic strength of 0.2 M. Under amine excess pseudo-first-order rate coefficients (kobs) are obtained. Plots of kobs against free amine concentration at constant pH are linear, with slopes kN. The BrAnsted plots (log kN vs. anilinium pKa) for the anilinolysis of 1-3 are linear, with slope (β) values of 0.52, 0.61, and 0.63, respectively. The values of these slopes and other considerations suggest that these reactions are ruled by a concerted mechanism. For these reactions, the kN values follow the reactivity sequence: 3 > 2 > 1. Namely, the reactivity increases as the number of nitro groups attached to the nonleaving group increases. Comparison of the reactions of this work with the stepwise pyridinolysis of carbonates 1-3 indicates that the zwitterionic tetrahedral intermediate (T±) formed in the pyridinolysis reactions is destabilized by the change of its pyridino moiety by an isobasic anilino group. This is attributed to the superior leaving ability from the T± intermediate of anilines, relative to isobasic pyridines, which destabilize kinetically this intermediate. The kN values for the anilinolysis of carbonates 1-3 are similar to those found in the reactions of these carbonates with secondary alicyclic amines. With the kinetic data for the anilinolysis of the title substrates and 4-methylphenyl and 4-chlorophenyl 2,4-dinitrophenyl carbonates, a multiparametric equation is derived for log kN as a function of the pKa of the conjugate acids of anilines and nonleaving groups.
