Theoretical and Experimental Local Reactivity Parameters of 3‑Substituted Coumarin Derivatives
Résumé
Local reactivity descriptors, such as atomic charges, atomic electrostatic potential and
atomic Fukui indices were computed for a series of 3-substituted coumarin (2-oxo-2H-1-benzopyran)
derivatives, using density functional theory (DFT) and Möller−Plesset methods (MP2). The variation
of those properties as a function of the substituents was compared with the variation of the measured
XPS binding energies. The atomic electrostatic potentials and XPS binding energies serves as indicators
of the electrophilicity of a given center within a molecule, while the atomic Fukui indices describe its
degree of electronic localization, known as atomic softness. The correlation between those theoretical
and experimental properties allowed us to follow the effect of electron withdrawing substituents on the
electrophilicity of a given atomic center. The Fukui indices provided additional information about the
softening/hardening of the center of interest due to presence of different substituents to the coumarin system. On the basis of
these analysis, the 1,2-addition would be favored for 3-acetyl, 3-phosphono, and 7-diethylamino substituents, while 3-carboxyl, 3-
ethoxycarbonyl, and 3-nitro substituent would favor 1,4-addition. The substituted coumarins would preferably react with soft
nucleophiles at position 2 and with hard nucleophiles at position 4.