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

Abstract

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/augcc-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 M H distances and by the consequent bond and dihedral angles distortions relatively to the cyclohexane structure.

Molecular structure and conformational properties of N-cyclohexylpiperidine as studied by gas-phase electron diffraction, mass spectrometry, IR spectroscopy and quantum chemical calculations

“…N-derivatives of cyclohexane also demonstrate preference of equatorial conformers. For example, B3LYP/augcc-pVDZ calculations of cyclohexylamine [33] predict 95 % overall content of both possible, trans and gauche, equatorial conformers in a gas phase, coinciding with our calculation for this compound at MP2/6-311G** level, about 74 %.…”

Conformational study of charged cyclohexyldiamines and their gas phase acid–base properties

“…A considerable number of papers on the structure of uncharged diamines in different media are published in literature [7][8][9]. Regarding charged diamines, some works have been performed in a,x-alkanediamines [10][11][12][13][14][15], but none in cyclic aliphatic diamines.…”

“…The data available on the gas phase structure of neutral CHDAs [9,14] show that the equatorial configuration of the amino group is favoured relative to the axial one [14]. Furthermore, no significant stabilization results from the formation of an intramolecular hydrogen bond between the groups.…”

Computational evaluation concerning the deviation of the atoms in 1- and 4-postions on the six-member ring and the effects on 1HNMR chemical shift

“…The silly but convenient names "chair" and "boat" came later.) Moreover, from this type of compounds valuable information on the structural point of view has been reported [8][9][10][11][12]. Furthermore, the conformational analysis of these compounds is particularly well developed [13][14][15][16][17][18].…”