Kinetics and Mechanism of the Hydrolysis of N-(Benzenesulfonyl) benzimidoyl Chlorides

摘要

The rates of hydrolysis of N-(benzenesulfonyl) benzimidoyl chlorides (p-H, p-CH3, p-CH3, p-NO2 and m-NO2) have been measured by UV spectrometry in 60% methanol-water at 25∩ and a rate equation which can be applied over wide pH range was obtained. Below pH 7.00, the substituent effect on the hydrolysis rate of N-(benzenesulfonyl) benzimidoyl chloride was found to conform to the Hammett ヲ constant with ヱ = -0.91, whereas above pH 9.00, with ヱ = 0.94. On the basis of the rate equation obtained and the effect of solvent, substituents and salt, the following reaction mechanism were proposed; below pH 7.00, the hydrolysis of N-(benzenesulfonyl) benzimidoyl chloride proceeds by SN1 mechanism, however, above pH 9.00, the hydrolysis is initiated by the attack of the hydroxide ion and in the range of pH 7.00-9.00, these two reactions occur competitively.