Substituent Effects on the Hydrolysis of m-Substituted Benzonitriles in Sulfuric Acid Solutions at 25.0 ±0.1 °C

The rate constants (kobs) for acid hydrolysis of m-substituted benzonitriles have been measured spectrophotometrically in sulfuric acid solutions (10.0 M to 18.2 M) at 25.1±0.1 oC. The logarithms kobs were correlated with different substituent constants (inductive and resonance). The results indicate in 10.0 M sulfuric acid that the rate constants are enhanced by electron-releasing (inductive effect) and the protonation of m-substituted benzonitriles was most probably slower than the nucleophilic addition. In 18.2 M sulfuric acid, the rate-determining step for the hydrolysis of benzonitriles was the addition of nucleophile which is enhanced by electron-withdrawing (inductive effect). A combination of the two mechanisms were most likely occurred in 13.0 to 17.0 M sulfuric acid solutions.