The Effect of Alkali Metal Ions on Nucleophilic Substitution Reactions of Aryl 2-Furoates with Alkali Metal Ethoxides in Ethanol

摘要

Rate constants have been measured spectrophotometrically for the nucleophilic substitution reactions of p-and m-nitrophenyl 2-furoates (4 and 5, respectively) with alkali metal ethoxides (EtO-M+) in absolute ethanol at 25∩. The reactivity of EtO-M+ toward 4 is in the order EtO-K+ > EtO-Na+ > EtO-Li+ > EtO-K+ + 18-crown-6 ether. This is further confirmed by an ion pairing treatment method. The present result indicates that (1) ion paired EtO-M+ is more reactive than dissociated EtO- ; (2) the alkali metal ions (K+, Na+, Li+) behave as a catalyst; (3) the catalytic effect increases with increasing the size of the metal ion. A similar result has been obtained for the reaction of 5, however, the catalytic effects shown by the metal ions are more significant in the reaction of 5 than in that of 4.