THE EFFECT OF ALKALI-METAL IONS ON NUCLEOPHILIC-SUBSTITUTION REACTIONS OF ARYL 2-FUROATES WITH ALKALI-METAL ETHOXIDES IN ETHANOL

Rate constants have been measured spectrophotometrically for the nucle ophilic substitution reactions of p- and m-nitrophenyl 2-furoates (4 a nd 5, respectively) with alkali metal ethoxides (EtO(-)M(+)) in absolu te ethanol at 25 degrees C. The reactivity of EtO(-)M(+) toward 4 is i n 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 re active than dissociated EtO(-); (2) the alkali metal ions (K+, Na+, Li +) behave as a catalyst; (3) the catalytic effect increases with incre asing the size of the metal ion. A similar result has been obtained fo r 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.