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Kinetics and mechanism of the aminolysis of p ‐nitrophenyl N ‐phenylcarbamates
Author(s) -
Koh Han Joong,
Kim Ok Sun,
Lee Hai Whang,
Lee Ikchoon
Publication year - 1997
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/(sici)1099-1395(199710)10:10<725::aid-poc943>3.0.co;2-x
Subject(s) - chemistry , aminolysis , benzylamine , kinetic isotope effect , deprotonation , tetrahedral carbonyl addition compound , reaction rate constant , medicinal chemistry , stereochemistry , acetonitrile , kinetics , deuterium , computational chemistry , organic chemistry , catalysis , nucleophile , ion , physics , quantum mechanics
Kinetic studies of the reactions of p ‐nitrophenyl N ‐phenylcarbamates with benzylamines were carried out in acetonitrile at 25·0 °C. Second‐order ( k 2 ) and third‐order ( k 3 ) rate constants were observed for all the Y‐substituted carbamates except for Y= m −Cl. The relatively large magnitude of ρ X (for X‐substituted benzylamines) and ρ Y together with a positive cross‐interaction constant ρ XY supports a stepwise mechanism involving rate‐limiting breakdown of the zwitterionic tetrahedral intermediate T ± . Kinetic isotope effect studies with deuterated benzylamine (XC 6 H 4 CH 2 ND 2 ) indicate that in the base‐catalyzed path, k 3 , rate‐limiting deprotonation occurs at the amino group of benzylamine within the T ± intermediate. The low δ H ≠ and δ S ≠ values for the k 3 process are in accord with the proposed mechanism © 1997 John Wiley & Sons, Ltd.