On the stability of methyl cations with aromatic substituents. Theoretical approach

The extreme stability of methyl cations surrounded by certain aromatic fragments was studied using density functional theory methods. The pKR+, aromaticity, ionization potential and dipole moment of tris[6-(dimethylamino)-1-azulenyl]methyl [1] and 2,6,10-tris(dimethylamino)trioxatriangulenium [2], as well as the corresponding for crystal violet [3] and tert-butanol [4], these last as the reference precursors of stable carbenium, were calculated and the results were found to be in agreement with experimental results previously reported. Furthermore, the calculations suggest that the large stability is a direct consequence of inductive effects as well as the intrinsic aromaticity of the branches as measured by the HOMA (harmonic oscillator model of aromaticity) method.