57238-80-9Relevant articles and documents
Kinetics and mechanism of the reactions of S-4-nitrophenyl 4-methylthiobenzoate with secondary alicyclic amines and pyridines
Castro, Enrique A.,Aguayo, Raul,Bessolo, Jorge,Santos, Jose G.
, p. 555 - 561 (2007/10/03)
The reactions of the title substrate with a series of six secondary alicyclic amines and a series of eight pyridines are subjected to a kinetic investigation in 44 wt% ethanol-water, at 25.0°C, and an ionic strength of 0.2 mol · dm-3. Under amine excess pseudo first-order rate coefficients (kobs) are obtained. Plots of kobs against free amine concentration at constant pH are linear, with the slope (k N) independent of pH. The Bronsted-type plots (log k N against pKa of the conjugate acids of the amines) are non-linear, with the curvature center located at pKa (pX a0) 9.7 and 9.4, for the reactions of secondary alicyclic amines and pyridines, respectively. The plots are consistent with a zwitterionic tetrahedral intermediate (T±) on the reaction path and a change in rate-determining step. The greater pKa0 value for secondary alicyclic amines than pyridines is explained by the greater nucleofugality from T± of secondary alicyclic amines compared to isobasic pyridines. These pKa0 values are lower than those found for the reactions of S-4-nitrophenyl 4-Y-substituted thiolbenzoates (Y = H, Cl, NO2) with the corresponding amine series. These results indicate that electron donation from the non-leaving group in T ± favors leaving group expulsion from T± relative to amine expulsion. Copyright
Effect of Acyl Substituents on the Reaction Mechanism for Aminolyses of 4-Nitrophenyl X-Substituted Benzoates
Um, Ik-Hwan,Min, Ji-Sook,Ahn, Jung-Ae,Hahn, Hyun-Joo
, p. 5659 - 5663 (2007/10/03)
Second-order rate constants (kN) have been measured spectrophotometrically for the reaction of 4-nitrophenyl X-substituted benzoates with a series of alicyclic secondary amines in H2O containing 20 mol % dimethyl sulfoxide at 25.0°C.
