Abstract
Kinetic study of isotope exchange reaction between p-nitrophenyl acetate and acetic anhydride in pyridine showed that one half of the radioactivity of acetic anhydride was employed for the exchange reaction. The result agreed with that of exchange reaction between acetic acid and p-nitrophenyl acetate, and the reaction showed exact linearity of log (1-F) vs. t. The exchange rate N was shown to be the first order function with respect to the ester and the acid. From the experiments carried out at 45.0°, 37.0°, 25.5°, and 0°, 14.7 kcal./mole was estimated for Ea. The mechanism, nucleophilic attack of acetoxyl group to the positive center of carbonyl group in the ester followed by acyloxygen fission, was considered to be most probable.
