57238-78-5Relevant articles and documents
Kinetic investigation of the reactions of S-4-nitrophenyl 4-substituted thiobenzoates with secondary alicyclic amines in aqueous ethanol
Castro, Enrique A.,Bessolo, Jorge,Aguayo, Raul,Santos, Jose G.
, p. 8157 - 8161 (2003)
The reactions of S-4-nitrophenyl 4-X-substituted thiobenzoates (X = H, Cl, and NO2: 1, 2, and 3, respectively) with a series of secondary alicyclic amines (SAA) were subjected to a kinetic investigation in 44 wt % ethanol-water, at 25.0 °C and an ionic strength of 0.2 M (KCl). The reactions were followed spectrophotometrically by monitoring the release of 4-nitrobenzenethiolate anion at 420-425 nm. Under excess amine, pseudo-first-order first-order rate constants (kobsd) are obtained for all reactions. The plots of kobsd vs [SAA] at constant pH are linear with the slope (kN) independent of pH. The statistically corrected Bronsted-type plots (log kN/q vs pKa + log p/q) for the reactions of 1 and 2 are nonlinear with slopes at high pK a, β1 = 0.27 and 0.10, respectively, and slopes at low pKa, β2 = 0.86 and 0.84, respectively. The Bronsted curvature is centered at pKa (pKa 0) 10.0 and 10.4, respectively. The reactions of SAA with 3 exhibit a linear Bronsted-type plot of slope 0.81. These results are consistent with a stepwise mechanism, through a zwitterionic tetrahedral intermediate (Ti±). For the reactions of 1 and 2, there is a change in rate-determining step with amine basicity, from T± breakdown to products at low pKa, to T± formation at high pKa. For the reactions of 3, breakdown to products of T ± is rate limiting for all the SAA series (pKa 0 > 11). The increasing pKa0 value as the substituent in the acyl group becomes more electron withdrawing is attributed to an increasing nucleofugality of SAA from T±. The greater pKa0 value for the reactions of SAA with 1, relative to that found in the pyridinolysis of 2,4-dinitrophenyl benzoate (pK a0 = 9.5), is explained by the greater nucleofugality from T± of the former amines, compared to isobasic pyridines, and the greater leaving ability from T± of 2,4-dinitrophenoxide relative to 4-nitrobenzenethiolate.
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.
