Kinetics and Mechanism of Hydrolysis of N-Arylphthalimides

Kinetics and Mechanism of Alkaline Hydrolysis of N-(o-Aminophenyl)Phthalimide in the Presence and Absence of Cationic Micelles and Sodium Salts of Aliphatic Acids

Pseudo first-order rate constants, k obs, for the alkaline hydrolysis of N-( o-aminophenyl) phthalimide, obtained at constant [CTABr]T (total concentration of cetyltrimethylammonium bromide) and varying concentrations of inert salt MX (MX = sodium formate, sodium acetate, sodium propanoate, sodium butyrate, sodium valerate and sodium hexanoate) follow the relationship: [Formula: see text], where θ and KX/S are empirical constants and S = HO-. The values of KX/S for each aliphatic acid decrease with an increase in [CTABr]T. This relationship gives an empirical constant whose magnitude is the measure of the ability of an ion, X-, to expel another counterion S-, from the cationic micellar surface to the bulk aqueous phase. The values of the empirical constant, KX/S, are used to derive the ion exchange constant, KBrX.

Kinetic evidence for near irreversible nonionic micellar entrapment of N-(2'-Methoxyphenyl)phthalimide (1) under the typical alkaline reaction conditions

The values of pseudo-first-order rate constants (k_obs) for alkaline hydrolysis of 1, obtained at 1.0 mM NaOH and within [ C_mE_nT] (total concentration of C_mE_n) range of 3.0–5.0 mM for C₁₂E₂₃ and 10–20 mM for C₁₈E₂₀, fail to obey pseudophase micellar (PM) model. The values of the fraction of near irreversible C_mE_n micellar trapped 1 molecules (F_IT1) vary in the range ~0–0.75 for C₁₂E₂₃ and ~0–0.83 for C₁₈E₂₀ under such conditions. The values of F_IT1 become 1.0 at ≥10 mM C₁₂E₂₃ and 50 mM C₁₈E₂₀. Kinetic analysis of the observed data at ≥10 mM C₁₂E₂₃ shows near irreversible micellar entrapment of 1 molecules under such conditions.

Effects of nonionic micelles on the rate of alkaline hydrolysis of N-(2'-methoxyphenyl)phthalimide (1): kinetic and rheometric evidence for a transition from spherical to rodlike micelles under the typical reaction conditions

Pseudo-first-order rate constants (k(obs)) for alkaline hydrolysis of N-(2'-methoxyphenyl)phthalimide (1) decrease nonlinearly with increasing total concentration of nonionic surfactant C(m)E(n) (i.e. [C(m)E(n)](T) where m and n represent the respective number of methyl/methylene units in the tail and polyoxyethylene units in the headgroup of a surfactant molecule and m/n=16/20, 12/23 and 18/20) at constant 2% v/v CH(3)CN and 1.0 mM NaOH. The k(obs)vs. [C(m)E(n)](T) data follow the pseudophase micellar (PM) model at ≤ 50 mM C(16)E(20), ≤ 1.4 mM C(12)E(23) and ≤ 2.0 mM C(18)E(20) where rate of hydrolysis of 1 in micellar pseudophase could not be detected. The values of k(obs) fail to follow the PM model at > ∼50 mM C(16)E(20), > ∼1.4 mM C(12)E(23) and > ∼2.0 mM C(18)E(20) which has been attributed to a micellar structural transition from spherical to rodlike which in turn increases C(m)E(n) micellar binding constant (K(S)) of 1 with increasing values of [C(m)E(n)](T). Rheological measurements show the presence of spherical micelles at ≤ 50 mM C(16)E(20), ≤ 1.4 mM C(12)E(23) and ≤ 3.0 mM C(18)E(20). The presence of rodlike micelles is evident from rheological measurements at > ∼50 mM C(16)E(20), > ∼1.4 mM C(12)E(23) and > ∼3.0 mM C(18)E(20).