title: Aminolysis of phenyl N-phenylcarbamate via an isocyanate intermediate: theory and experiment.
abstract: A comprehensive examination of the mechanism of the uncatalyzed and base-catalyzed aminolysis of phenyl N-phenylcarbamate by theoretical quantum mechanical methods at M06-2X/6-311+G(2d,2p) and B3LYP-D3/6-31G(d,p) levels, combined with an IR spectroscopic study of the reaction, was carried out. Three alternative reaction channels were theoretically characterized: concerted, stepwise via a tetrahedral intermediate, and stepwise involving an isocyanate intermediate. In contrast to dominating views, the theoretical results revealed that the reaction pathway through the isocyanate intermediate (E1cB) is energetically favored. These conclusions were supported by an IR spectroscopic investigation of the interactions of phenyl N-phenylcarbamate with several amines possessing varying basicities and nucleophilicities: n-butylamine, diethylamine, triethylamine, N-methylpyrrolidine, and trimethylamine. The reactivity of substituted phenyl N-phenylcarbamates in the aminolysis reaction was rationalized using theoretical and experimental reactivity indexes: electrostatic potential at nuclei (EPN), Hirshfeld and NBO atomic charges, and Hammett constants. The obtained quantitative relationships between these property descriptors and experimental kinetic constants reported in the literature emphasize the usefulness of theoretical parameters (EPN, atomic charges) in characterizing chemical reactivity.
authors.affiliation: Department of Chemistry and Pharmacy, University of Sofia, Sofia 1164, Bulgaria. silieva@chem.uni-sofia.bg
authors.forename: Sonia
authors.initials: S
authors.lastname: Ilieva
authors.forename: Didi
authors.initials: D
authors.lastname: Nalbantova
authors.forename: Boriana
authors.initials: B
authors.lastname: Hadjieva
authors.forename: Boris
authors.initials: B
authors.lastname: Galabov
mesh_terms: D000641:Ammonia / Q000737:chemistry*; D002219:Carbamates / Q000138:chemical synthesis* / Q000737:chemistry; D017953:Isocyanates / Q000737:chemistry*; D015394:Molecular Structure; D011789:Quantum Theory
chemical_list: D002219:Carbamates; D017953:Isocyanates; D000641:Ammonia