Kinetics and Mechanism of Hydrolysis of N-Arylphthalimides

Abstract

The values of pseudo-first-order rate constants, kobs, for hydrolysis of N-(2'-methoxyphenyl)phthalimide (1) increase linearly with increase in [HCl] over the range 5 × 10−3 - 1.0M at 8.0 × 10−5 M 1, 0.5M μ (by NaCl) and in the temperature range 30-40°C. The rate of acidic hydrolysis of N-(4'-methoxyphenyl)phthalimide (2) reveals behaviour similar to that found for 1, N-(2'-hydro-xyphenyl)phthalimide (3) and N-(4 ‘-aminophenyl)phthalimide (4). The values of kobs at 35°C and varying [HCl] give the respective rate constants for the [HCl]-independent (k0) and the [HCl]-dependent (kH) hydrolysis of 1 (at [10] = 8.0 × 10−5 M, μ = 0.5 M) as 6.74 ×10−7 s−1 and 5.47 × 10−6 M−1 s−1, 2 (at [20] = 3.0 × 10−5M, μ = 0.5 M) as 12.2 × 10−7 s−1 and 4.61 × 10−6 M−1 s−1 and 4H+ (at [40] = 2.0 × 10−4 M, μ = 1.0 M) as 5.83 × 10−7 s−1 and 15.2 × 10−6 M−1 s−1. The values of kw/k0min are of the order of 102 for 1, 2 and 4 where k0min represents the sum of the contributions of H+ - and HO- -catalysed hydrolysis towards k0 (first-order rate constant for pH-independent hydrolysis of imide) and kw is the pseudo-first-order rate constant for the uncatalysed reaction of H2O with imide.

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

“…The value of pseudo-first-order rate constant (k W ) for pH-independent hydrolysis of 1 at 35°C is 6.74 Â 10 À7 s À1 [21]. It is evident from Table 1 that the value of k obs , at [C 16 E 20 ] T = 0, is 32.3 Â 10 À3 s À1 which is $4.8 Â 10 4 -fold larger than that of k w .…”

“…The reports on the change of order of a reaction/reaction mechanism with the change of reaction medium from aqueous phase to micellar phase are rare. Thus, a brief reaction mechanism for alkaline hydrolysis of 1 may be represented by Scheme 2 where k 1 -step is the rate-determining step [21,29]. In Scheme 2, T À represents highly reactive monoanionic tetrahedral intermediate.…”

“…the data analysis are described elsewhere [21]. The product characterization study was carried out spectrophotometrically.…”

Kinetic Evidence for Near Irreversible Nonionic Micellar Entrapment ofN-(2′-Methoxyphenyl)phthalimide (1) under the Typical Alkaline Reaction Conditions

“…The values of k 1 were found to decrease by ~3-fold, while the values of k 2 remained unchanged with the increase of [C 16 E 10 ] T from 50 to 88 mM in the aqueous cleavage of 3 [11]. Although the calculated values of k 1 are not very reliable because they are derived from only either two or one data point(s), these values of k 1 appear to be plausible for the reason that the value of k 1 at pH ~3.5, in mixed aqueous solvent containing 2% v/v CH 3 CN, is 67 × 10 −8  s −1 [16]. Under such typical conditions, the value of k 2 is 120 × 10 −5  s −1 and it decreases from 120 × 10 −5 to 6.6 × 10 −5  s −1 with increase in CH 3 CN content from 2 to 82% v/v [15].…”

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

“…All chemicals used were commercial products of premier available purity except NOAIM which was synthesised using the reported procedure [26].…”