22113-51-5Relevant articles and documents
Kinetic study on alkaline hydrolysis of Y-substituted phenyl picolinates: Effects of modification of nonleaving group from benzoyl to picolinyl on reactivity and reaction mechanism
Kim, Myung-Joo,Kim, Min-Young,Um, Ik-Hwan
, p. 1138 - 1142 (2015/07/15)
Second-order rate constants (kOH-) for alkaline hydrolysis of Y-substituted phenyl picolinates (6a-6i) have been measured spectrophotometrically. A linear Bronsted-type plot is obtained with βlg = -0.34, which is typical for reactions reported previously to proceed through a stepwise mechanism with formation of an addition intermediate being the rate-determining step (RDS). However, σYo constants result in a much poorer Hammett correlation than σY- constants. Furthermore, the Yukawa-Tsuno plot exhibits an excellent linear correlation with ρY = 0.82 and r = 0.72, indicating that a negative charge develops partially on the O atom of the leaving group in the RDS. Thus, the reactions have been concluded to proceed through a forced concerted mechanism with a highly unstable intermediate 7. Comparison of the current kinetic data with those reported previously for the corresponding reactions of Y-substituted phenyl benzoates has revealed that modification of the nonleaving group from benzoyl to picolinyl causes not only an increase in reactivity but also a change in the reaction mechanism (i.e., from a stepwise mechanism to a forced concerted pathway).
Kinetics and mechanistic study of the reaction of cyclic anhydrides with substituted phenols. Structure-reactivity relationships
Andres, Gabriel O.,De Rossi, Rita H.
, p. 1445 - 1449 (2007/10/03)
(Chemical Equation Presented) The kinetic of the reactions of phthalic and maleic anhydrides with different substituted phenols (Z-PhOH with Z = H, m-CH3, p-CH3, m-Cl, p-Cl, and m-CN) were studied in aqueous solution. Two kinetic processes well separated in time were observed. The fast one is attributed to the formation of the aryl ester in equilibrium with the anhydride and allows the determination of the rate of nucleophilic attack of the phenol on the anhydride (k-A). From the slow kinetic process, the equilibrium constant for this reaction was determined. The Broensted-type plots for the nucleophilic attack of substituted phenols on the anhydrides were linear with slopes βNuc of 0.45 and 0.56 for phthalic and maleic anhydride, respectively. The results are consistent with a mechanism involving rate-determining nucleophilic attack and also with a concerted mechanism. The calculated effective charge on the atoms involved in the reactions and the Broensted β values are consistent with a mechanism involving a concerted or enforced concerted mechanism where a tetrahedral intermediate with significant lifetime is not formed along the reaction coordinate. The latter mechanism is preferred over the stepwise process.
Curved Hammett Plot in Alkaline Hydrolysis of O-Aryl Thionobenzoates: Change in Rate-Determining Step versus Ground-State Stabilization
Um, Ik-Hwan,Lee, Ji-Youn,Kim, Han-Tae,Bae, Sun-Kun
, p. 2436 - 2441 (2007/10/03)
Second-order rate constants have been measured for alkaline hydrolysis of O-aryl thionobenzoates (X-C6H4-CS-OC6H 4-Y) in 80 mol % H2O-20 mol % DMSO at 25.0 ± 0.1 °C. The Hammett plot for the reaction of O-4-nitrophenyl X-substituted thionobenzoates (X-C6H4-CS-OC6H 4-NO2, 1a-e) exhibits a downward curvature. However, a possible traditional explanation in terms of a change in the rate-determining step (RDS) has been considered but rejected. The proposed explanation involves stabilization of the ground-state (GS) through-resonance interaction between the electron-donating substituent X and the thionocarbonyl functionality on the basis of the linear Yukawa-Tsuno plot obtained for the same reaction. The Bronsted-type plot for the reaction of O-aryl thionobenzoates (C 6H5-CS-OC6H4-Y, 2a-i) is linear but exhibits many scattered points with a small βlg, (-0.35). The Hammett plot for the same reaction shows rather poor correlation with σ- constants but much better correlation with σ° constants. The alkaline hydrolysis of O-aryl thionobenzoates (1a-e and 2a-i) has been proposed to proceed through an addition intermediate in which bond formation is the RDS.