Geometric structure, electronic structure, and some thermodynamic properties of C13H22 trimethyl- and ethylmethyladamantanes

The structure of perhydrofluorene and its isomerization products 1,3,5-trimethyladamantane, 1,3,6-trimethyladamantane, cis-1,3,4-trimethyladamantane, trans-1,3,4-trimethyladamantane, 1-ethyl-3-methyladamantane, cis-1-ethyl-4-methyladamantane, trans-1-ethyl-4-methyladamantane, 1,2,6-trimethyladamantane, and 1,2,8-trimethyladamantane of the general formula C13H22 has been studied using the Becke—Lee—Yang—Parr (B3LYP) hybrid energy functional of electron density with the 6-31G* basis set. The geometric and electronic characteristics of the compounds and their total energy, transformation energies, entropies of transformations, and normal vibration frequencies have been calculated. It has been shown that the calculated Gibb free energies of formation for the perhydrofluorene isomerization products are in qualitative agreement with the experimental product composition of the isomerate.