Molecular structure of mono- and 1,2-aminoderivatives of cyclohexane: Steric strain effects as determining factors

The conformational study of cyclohexylamine and 1,2-cyclohexylamine derivatives was performed. The potential energy surface of every compound was calculated at B3LYP/6-31G(d) and the conformational energy minima were further optimized at B3LYP/aug-cc-pVDZ level of theory. The geometrical parameters and the electronic energy of each conformer were determined. The internal energy, enthalpy, entropy, Gibbs energy and the relative weight of each conformer in the structure of the respective isomer were calculated at 298.15 K. The steric hindrances in the crowded molecules resulting from the replacement of hydrogens of cyclohexane by amine groups are pointed out by short non-bonded H ↔ H distances and by the consequent bond and dihedral angles distortions relatively to the cyclohexane structure.