Hydrolysis of para ‐substituted benzonitriles in water

The transformation of para ‐substituted benzonitriles was studied in buffered distilled water. The elevated temperature experiments revealed that benzonitriles are hydrolyzed to the corresponding benzoic acids through benzamide intermediates. For 4‐chlorobenzonitrile, the pseudo‐first‐order rate constants adhered to the Arrhenius equation with an activation energy of 40.5 kJ · mol −1 and collision frequency of In 6.23 × 10 4 . Alkaline hydrolysis was dominant at pH values above 8, while neutral hydrolysis was important between pH 5 and 7. The quantitative structure‐reactivity relationship (QSRR) analysis of 14 para ‐substituted benzonitriles showed that the first‐order rate constants obtained in phosphate buffer (pH 7.7) at 85°C, based on a combination of neutral and alkaline hydrolysis, were correlated with Hammett σ p constants.