title: Analysis of the effects of N-substituents on some aspects of the aromaticity of imidazoles and pyrazoles.
abstract: The influence of the N-substituent on the aromaticity of azoles is a subject that has not yet been addressed in detail, in contrast to the good understanding of the corresponding C-substitution. In the present work, we analyze the aromaticities of a series of 1,2- and 1,3-azoles (pyrazoles and imidazoles, respectively) with the N-substituents NH(2), OH, Cl, SH, H, NO(2), CN, SO(2)F, SO(2)CF(3), and N(SO(2)CF(3))(2), which are also compared with the aromaticities of the corresponding substituted benzene series. The larger stabilitiy of the imidazole ring is due not to a higher aromaticity, but rather to the weakness of the N-N bond in the pyrazole series. The aromaticity of azoles was found to be significantly less robust to N-substitutions than that of their C-substituted benzene counterparts.
authors: Institut de Química Computacional and Departament de Química, Universitat de Girona, Campus de Montilivi, 17071 Girona, Spain.
authors: Carles
authors: C
authors: Curutchet
authors: Jordi
authors: J
authors: Poater
authors: Miquel
authors: M
authors: Solà
authors: José
authors: J
authors: Elguero
mesh_terms: D007093:Imidazoles / Q000737:chemistry*; D015394:Molecular Structure; D011720:Pyrazoles / Q000737:chemistry*; D011789:Quantum Theory; D013237:Stereoisomerism
chemical_list: D007093:Imidazoles; D011720:Pyrazoles