Kinetic studies on general base-catalyzed cleavage of phthalimide (PTH) in 2-hydroxyethylamine and 2-methoxyethylamine buffers

Abstract

Kinetic studies on the nucleophilic cleavage of phthalirnide [ PTH) in buffers of 2-hydroxyethylarnine and 2-rnethoxyethylarnine reveal nonlinear plots of k, vs I Bufl, (at constant pH) where k, and IBuf], represent apparent second-order rate constant and total arnine buffer concentration, respectively. The nonlinear variation of k, against [BuflT is attributed to the occurrence of a stepwise mechanism in the aminolysis of PTH Intermolecular general base catalysis is detected in the reactions of both arnines with nonionized PTH (SH) only within the pH range of the present study 0 1996 john Wiley &Sons, Inc

Kinetics and Mechanism of the Cleavage of N-Phthaloylglycine in Buffers of Some Primary Amines

“…The calculated values of K 1 1 k 2 1 and k -2 1 / k 4 1' from respective equations ( 7) and ( 8) are (7.80 ± 1.78) × 10 -2 dm 6 /mol 2 /s 1 and 3.3 ± 1.4 dm 3 /mol 1 for CH 3 OCH 2 CH 2 NH 2 with pK a Am = 9.45 26 and (17.6 ± 5.4) × 10 -2 dm 6 /mol 2 s 1 and 2.7 ± 0.3 dm 3 /mol for HOCH 2 CH 2 NH 2 with pK a Am = 9.60. 27 The value of K 1 1 k 2 1 (= 0.078 dm 6 9 are nearly 30-and 50fold larger than those with NPG which could be explained in terms of polar effects within the limits of standard deviations of the calculated values of K 1 1 k 2 1 . Addendum: General base catalysis could be detected kinetically in the cleavages of NPG and phthalimide (PTH) in the buffer solutions of 2-methoxyethylamine, 2-hydroxyethylamine and hydrazine.…”

“…Thus, in continuation of such study, we have carried out rate studies on the reactions of NPG with 2-methoxyethylamine and 2-hydroxyethylamine because GB catalysis was observed in the reactions of these amines with phthalimide. 9 The observed results and their probable explanation(s) are described in this manuscript.…”

“…1a The other possible reasons for the nonlinear dependence of k n app on [Am] T may be ruled out as discussed elsewhere in the related reacting system. 9 The simplest mechanism which could explain the observed data is shown in Scheme 1…”

Kinetics and mechanism for the formation of o‐carboxy(N‐methyl)‐benzohydroxamic acid in the cleavage of ethyl N‐[o‐(N‐methyl‐N‐hydroxycarbamoyl)‐benzoyl]carbamate in N‐methylhydroxylamine, acetate, and phosphate buffers

“…The aqueous cleavage of phthalimide and substituted phthalimides in the presence of primary and secondary amines involves rather complex reaction mechanisms 1–8. Isolation of intermediates and end products in these reactions provides a fruitful insight about the mechanisms of these reactions.…”

Kinetic evidence for the occurrence of kinetically detectable intermediates in the cleavage of N‐ethoxycarbonylphthalimide under N‐methylhydroxylamine buffers

“…Phthalamide and N,N′‐disubstituted phthalamides undergo cyclization reactions to produce cyclized products such as imide and N‐substituted imides 11–16. Under typical reaction conditions, the reactions of N ‐hydroxyphthalimide with hydroxylamine 17 and N ‐methylhydroxylamine 18 produced cyclic stable intermediates formed presumably by the intramolecular nucleophilic attack of hydroxyl moiety at the most electrophilic carbonyl carbon of the respective aminolysis immediate products, o ‐( N ‐hydroxycarbamoyl)benzohydroxamic acid and o ‐( N ‐methyl‐ N ‐hydroxycarbamoyl)benzohydroxamic acid.…”