A theoretical study of the bond-dissociation enthalpies (BDH), N–R bond lengths and proton affinities of N-substituted pyrroles, imidazoles and pyrazoles with R substituents along the periodic table.

The properties (geometry, bond-dissociation enthalpies and proton affinities) of three azoles, pyrrole, imidazole and pyrazole, with twenty-two N-substituents R covering a significant part of the periodic table [1 (lithium group, alkaline), 2 (beryllium group, alkaline earth), 13 (boron group, triel), 14 (carbon group, tetrel), 15 (nitrogen group, pnictogen), 16 (oxygen group, chalcogen) and 17 (fluorine group, halogen) of the periods 2, 3 and 4 plus the hydrogen] have been calculated with the G4 composite ab initio method. These three properties were discussed with regard to the azole and to the group R using as model compound the amines H2N–R. The large set of compounds and their consistency allowed finding many equations that related different calculated properties. General properties such as bond-dissociation enthalpies, BDH, N–R bond lengths and proton affinities were tested in search of simple equations that explain the calculated properties. [ABSTRACT FROM AUTHOR]