Kinetic Studies on the Mechanism of Hydrolysis of Benzohydrazonyl Bromide

[摘要] The kinetics of hydrolysis of hydrazonyl bromides (p-H, p-CH3, p-OCH3, p-Br, p-Cl & p-NO2) have been investigated by UV spectrometry in 60% dioxane-water at 25¡É and a rate equation which can be applied over wide pH range was obtained. Below pH2, the rate of hydrolysis of a series of hydrazonyl bromide is accelerated by electrondonating group (¥ñ = -0. 94) whereas at the pH values greater than 4, the ¥ñ-value is 0.54. The rate equation, solvent-, substituent-and bromide ion-effect on the rate of hydrolysis are rationalized in terms of SN1 and SN2 mechanism: below pH 2, the hydrolysis proceed through SN2, however, above pH 4, the hydrolysis is started by the attack of hydroxide ion and in the range pH 2¡­4, these two reactions occur competitively.

[学科分类] 化学（综合）