EFFECT OF A SUBSTITUENT IN THE BENZENE-RING UPON THE KINETICS OF ACID-CATALYZED HYDROLYSIS OF EXO-2-NORBORNYL PHENYL ETHER

The rate constants of hydrolysis for exo-2-norbornyl phenyl ether with out substituent and with p-Me, p-Ac, m-CN, p-CN or p-NO2 group in the benzene ring were measured in concentrated perchloric acid solutions s pectrophotometrically and/or by capillary GC. The effect of the substi tuent on the rate constants and other kinetic parameters of hydrolysis is small. The parameters are in agreement with the A-1 mechanism. The ether oxygen of the exo-epimer is much more basic than that of the en do-epimer (pK(a,exo)-pK(a,endo)approximate to 2), which causes a great er part of the exo/endo rate ratio than do the initial state energies and rate constants of the rate limiting stage, i.e. of the formation o f the norbornyl cation and the substituted phenol.