The mechanism of hydrolysis of phthalamic and N-phenylphthalamic acid

Kinetics and mechanism of the cleavage of phthalic anhydride in glacial acetic acid solvent containing aniline

Apparent second-order rate constants (k(n)(app)) for the nucleophilic reaction of aniline (Ani) with phthalic anhydride (PAn) vary from 6.30 to 7.56 M(-1) s(-1) with the increase of temperature from 30 to 50 degrees C in pure glacial acetic acid (AcOH). However, the values of pseudo-first-order rate constants (k(s)) for the acetolysis of PAn in pure AcOH increase from 16.5 x 10(-4) to 10.7 x 10(-3) s(-1) with the increase of temperature from 30 to 50 degrees C. The values of k(n)(app) and k(s) vary from 5.84 to 7.56 M(-1) s(-1) and from 35.1 x 10(-4) to 12.4 x 10(-4) s(-1), respectively, with the increase of CH(3)CN content from 1% to 80% v/v in mixed AcOH solvents at 35 degrees C. The plot of k(s) versus CH(3)CN content shows a minimum (with 10(4) k(s) = 4.40 s(-1)) at 50% v/v CH(3)CN. Similarly, the variations of k(n)(app) and k(s) with the increasing content of tetrahydrofuran (THF) in mixed AcOH solvent reveal respective a maximum (with k(n)(app) = 17.5-15.6 M(-1) s(-1)) at 40-60% v/v THF and a minimum (with k(s) = approximately 0-1.2 x 10(-4) s (-1)) at 60-70% v/v THF. The respective values of DeltaH* and DeltaS* are 15.3 +/- 1.2 kcal mol(-1) and -20.1 +/- 3.8 cal K(-1) mol(-1) for k(s) and 1.1 +/- 0.5 kcal mol(-1) and -51.2 +/- 1.7 cal K(-1) mol(-1) for k(n)(app), while the values of k(n) (= k(n)(app)/f(b) with f(b) representing the fraction of free aniline base) are almost independent of temperature within the range 30-50 degrees C. A spectrophotometric approach has been described to determine f(b) in AcOH as well as mixed AcOH-CH(3)CN and AcOH-THF solvents. Thus, the observed data, obtained under different reaction conditions, have been explained quantitatively. An optimum reaction condition, within the domain of present reaction conditions, has been suggested for the maximum yield of the desired product, N-phenylphthalamic acid.

Effects of Mixed H2O—CH3CN and H2O—HCONMe2 Solvents on the Rate of Cleavage of N-Benzylphthalamic Acid

The values of pseudo first-order rate constants, k1, for the O-cyclization and k3 for N-cyclization of N-benzylphthalamic acid 1, obtained at 0.02 M HCl and 35°C, show a respective nonlinear increase from 17.6 × 10−6 to 29.7 × 10−6 s−1 and decrease from 12.5 × 10−7 to 3.75 × 10−7 s−1 with increase in the CH3CN content from 2 to 60% v/v in mixed aqueous solvent. Increase in the CH3CN content from 60 to 90% v/v decreases k1 from 29.7 × 10−6 to 24.4 × 10−6 s−1 and increases k3 from 3.75 × 10−7 to 14.7 × 10−7 s−1. The respective values of k1 and k3 decrease nonlinearly from 16.0 × 10−6 to 3.0 × 10−6 s−1 and 14.0 × 10−7 to ~4.0 × 10−7 s−1 with increase in the content of N,N-dimethylformamide (HCONMe2) from 2 to 80% v/v in mixed aqueous solvents. These results indicate rather mild rate-retarding effects of mixed H2O—CH3CN and H2O—HCONMe2 solvents on the rates of the intramolecular reactions.

Kinetic Coupled with UV Spectral Evidence for Near-Irreversible Nonionic Micellar Binding ofN-Benzylphthalimide under the Typical Reaction Conditions: An Observation Against a Major Assumption of the Pseudophase Micellar Model

Pseudo-first-order rate constants (k(obs)) for alkaline hydrolysis of N-benzylphthalimide (1) show a nonlinear decrease with the increase in [C(m)E(n)]T (total concentration of Brij 58, m = 16, n = 20 and Brij 56, m = 16, n = 10) at constant [CH(3)CN] and [NaOH]. These nonionic micellar effects, within the certain typical reaction conditions, have been explained in terms of the pseudophase micellar (PM) model. The values of micellar binding constants (KS) of 1 are 1.04 x 10(3) M(-1) (at 1.0 x 10(-3) M NaOH) and 1.08 x 10(3) M(-1) (at 2.0 x 10(-3) M NaOH) for C(16)E(20) as well as 600 M(-1) (at 7.6 x 10(-4) M NaOH) and 670 M(-1) (at 1.0 x 10(-3) M NaOH) for C(16)E(10) micelles. The pseudo-first-order rate constants (kM) for hydrolysis of 1 in C(16)E(20) micellar pseudophase are approximately 90-fold smaller than those (kW) in water phase. The values of kM for hydrolysis of 1 in C(16)E(10) micelles are almost zero. Kinetic coupled with UV spectral data reveals significant irreversible nonionic micellar binding of 1 molecules in the micellar environment of nearly zero hydroxide ion concentration at >or=0.14 M C(16)E(20) and 1.0 x 10(-3) M NaOH while such observations could not be detected at <or=0.17 M C(16)E(20) and 2.0 x 10(-3) M NaOH. Significantly, such irreversible C(16)E(10) micellar binding of 1 molecules could be detected at 8.8 x 10(-2) M C(16)E(10) and 1.0 x 10(-3) M NaOH as well as at >or=3 x 10(-3) M C(16)E(10) and 7.6 x 10(-4) M NaOH, while the rate of hydrolysis of 1 is completely ceased at >or=0.05 M C(16)E(10) and 7.6 x 10(-4) M NaOH. The rate of hydrolysis of 1 at 5.0 x 10(-2) and 8.8 x 10(-2) M C(16)E(10) and 1.0 x 10(-3) M NaOH reveals the formation of presumably phthalic anhydride, whereas such observation was not observed in the C(16)E(20) micellar system under similar experimental conditions.

Suggested Improvement in the Ing-Manske Procedure and Gabriel Synthesis of Primary Amines: Kinetic Study on Alkaline Hydrolysis of N-Phthaloylglycine and Acid Hydrolysis of N-(o-Carboxybenzoyl)glycine in Aqueous Organic Solvents

A slight modification of the Gabriel synthesis of primary amines is suggested on the basis of the observed and reported values of rate constants for the alkaline and acid hydrolyses of phthalimide, phthalamic acid, benzamide, and their N-substituted derivatives. The suggested procedure requires shorter reactions time and milder acid-base reaction conditions compared with the conventional acid-base hydrolysis in the Gabriel synthesis. A slight modification in the Ing-Manske procedure is also suggested. Pseudo-first-order rate constants, k(obs), for hydrolysis of N-phthaloylglycine, NPG, decrease from 24.1 x 10(-3) to 7.72 x 10(-3) and 6.12 x 10(-3) s(-1) with increasing acetonitrile and 1,4-dioxan contents, respectively, from 2 to 50% v/v (all the percentages given in the paper are vol %), while increasing the organic cosolvents content from 50 to 80% increases k(obs) from 7.72 x 10(-3) to 19.7 x 10(-3) s(-1) for acetonitrile and from 6.12 x 10(-3) to 52.8 x 10(-3) s(-1) for 1,4-dioxan, in aqueous organic solvents containing 0.004 M NaOH at 35 degrees C. The rate constants for NPG hydrolysis decrease from 2.11 x 10(-2) to 1.19 x 10(-4) s(-1) with increasing MeOH content from 2 to 84%, in aqueous organic solvents containing 2% MeCN and 0.004 M NaOH at 35 degrees C.

Aqueous degradation of N-(hydroxymethyl)phthalimide in the presence of specific and general bases. Kinetic assessment of N-hydroxymethyl derivatives of nitrogen heterocycles as possible prodrugs

The conversion of N-(hydroxymethyl)phthalimide (NHPH) to phthalimide could not be detected within 300 s at pH 9.0, whereas in 0.18 M NaOH complete conversion of NHPH to phthalimide was observed within 50 s. In the presence of 0.2-0.4 M 1,4-diazabicyclo[2.2.2]octane buffer solutions (pH 9.30-9.54), 40-60% conversion of NHPH to phthalimide occurred within 90-120 s. The initial concentration of NHPH affected the extent of conversion of NHPH to phthalimide.