Kinetics and mechanism of base-catalysed hydrolysis of phthalimide

Abstract

The kinetics of base-catalysed hydrolysis of phthalimide were studied at 1.02M ionic strength in alkaline medium. The data were found to be well fitted with a series first–order consecutive reaction mechanism. The sodium hydroxide concentration dependence of the reaction was found in accordance with k_1obs=B₁+B₂[OH^–] and k_2obs=C₁+C₂[OH^–] where k_1obs and k_2obs are rate constants corresponding to general reaction scheme A [graphic omitted] B [graphic omitted] X where A, B, and X stand for phthalimide, phthalamic acid, and ammonia, respectively. The hydrolysis was studied in the temperature range of 60–95 °C. The activation parameters corresponding to first and second consecutive steps of the reaction are: ΔH_I*= 19.9 ± 0.3 kcal mol^–1, ΔS_I*=–21.2 ± 0.8 cal K^–1 mol^–1; E_aI= 20.6 ± 0.3 kcal mol^–1, In A_I= 19.99 ± 0.75 s^–1, and ΔH_II*= 10.0 ± 0.5 kcal mol^–1; ΔS_II*=–50.9 ± 1.32 cal K^–1 mol^–1, E_aII= 10.7 ± 0.5 kcal mol^–1, In A_II= 6.02 ± 1.31 s^–1.