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.
Kinetics and mechanism of the reactions of S-2,4-dinitrophenyl 4-substituted thiobenzoates with secondary alicyclic amines
Castro, Enrique A.,Aguayo, Raul,Bessolo, Jorge,Santos, Jose G.
, p. 7788 - 7791 (2007/10/03)
The title reactions, in 44 wt % ethanol-water at 25.0 °C, exhibit slightly curved Bronsted-type plots (log kN versus pK a of amines) with slopes β1 = 0.1-0.44 (at high pKa) and β2 ca. 0.7 (at low pKa). The magnitude of some of these slopes, together with the fact that the curvature center (pKa0 = 9.5-10.8) does not change with the electronic effects of the benzoyl substituent, suggests that these reactions are not stepwise, but concerted.
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.
Structure-reactivity correlations in the reaction of 2,4-dinitrophenyl X-substituted benzoates with alicyclic secondary amines
Um, Ik-Hwan,Min, Ji-Sook,Lee, Hye-Won
, p. 659 - 666 (2007/10/03)
Apparent second-order rate constants (kapp) have been measured spectrophotometrically for the reaction of 2,4-dinitrophenyl X-substituted benzoates with a series of alicyclic secondary amines in H2O containing 20 mol% DMSO at 25°C. The microconstants involved in the reaction (k-1/k2, K1, and k1k2/k-1) have also been calculated. The magnitude of kapp, k1, and k1k2/k-1 values increases with increasing amine basicity and with increasing acid strengthening ability of the acyl substituent X. The k-1/k2 value decreases from ca. 6.5 to 0.3 with increasing the amine basicity, but remains almost constant upon changing the acyl substituent X for a given amine, indicating that the ratedetermining step is governed by the basicity of amine but not by the electronic nature of the acyl substituent X. The Bronsted-type plots for kapp show a break at pKa = 9.1, supporting the assumption that a change in the rate-determining step occurs from rate-limiting breakdown to formation of the addition intermediate as amine basicity increases. The corresponding Bronsted-type plots for k-1/k2, k1, and k1k2/k-1 are linear but their β values are different. σ+ constants show better correlation with log kapp, log kl and log k1k2/k-1 for the reaction with low basic amines (pKa a > 9.1). The magnitude of ρ1 is identical to that of ρapp and ρeq for a given amine.
