Carbinol Derivatives of N-(alpha-Hydroxybenzyl)benzamide: Acid and Base-Dependent Kinetics in Water and the Mechanistic Implications for Carbinolamide Reactivity

摘要

The kinetics of the aqueous reaction, between pH values of 0-4 & 7-14, have been determined for a series of carbinol substituted N-(alpha-hydroxybenzyl)benzamide derivatives (5), in H2O, at 25 degrees C, I=1.0 M (KCl). The carbinol derivatives of 5 were found to react via two mechanisms. Between pH values of 0 to 4, an acid-catalyzed mechanism was found and under neutral/basic conditions the carbinolamides reacted by a specific-base catalyzed mechanism (E1cB-like mechanism). No evidence for mechanistic variation of the acid and base-catalyzed reactions based upon the carbinol substituent was found. The rate constants are reported for the acid-catalyzed (k(H), rho=-1.89), the apparent second-order hydroxide rate constant (k'(1), rho=-0.16), hydroxide limiting rate (k(1), rho=-0.93) and the pK(a)'s of the hydroxyl group (rho=0.77) for seven carbinol substituted derivatives of 5. The rho-values for the carbinol derivatives of 5 will be compared to the previously reported rho-values for the structurally similar amide substituted derivatives.