Metal Ion Catalysis in Nucleophilic Substitution Reaction of 4-Nitrophenyl Picolinate with Alkali Metal Ethoxides in Anhydrous Ethanol †

Summary of second-order rate constants from ion-pairingtreatment of kinetic data for reactions of 6 with EtOM in anhydrousEtOH at 25.0 ± 0.1 o C. EtOM ‒ k EtO‒ /M 1 s ‒1 k EtOM /M ‒1 s k EtOM / k EtO‒ EtOK 48633706.93EtONa 385664017.2EtOLi 43613503.10 tively. Alkali metal ethoxides have been reported to exist as dimmers or other aggregates in a high concentration region (e.g., [EtOM] > 0.1 M). 14 However, it has been suggested that EtOM exists as dissociated and ion-paired species in concentration below 0.1 M. 14 Since the current reactions were performed in a low concentration region (e.g., [EtOM] < 0.012 M), one might expect that both dissociated EtO ‒ and ion-paired EtOM react with substrate 6 as shown in Scheme 2. EtOM Products + 6 EtO- + One M + EtO + 6 Products k EtOM k - K d Scheme 2 One can derive a rate equation as eq (1) based on the mecha-nism proposed in Scheme 2. Since the reactions were performed under pseudo-first-order conditions,