TY - JOUR
T1 - Intramolecular hydrogen bonding, Gauche interactions, and thermodynamic functions of 1,2-ethanediamine, 1,2-ethanediol, and 2-aminoethanol
T2 - A global conformational analysis
AU - Chang, Y. P.
AU - Su, T. M.
AU - Li, Ta-Wei
AU - Chao, Ito
PY - 1997/8/21
Y1 - 1997/8/21
N2 - The global conformational potentials of 1,2-ethanediol, 1,2-ethanediamine, and 2-aminoethanol (X-CH2-CH2-Y; X, Y = OH or NH2) were obtained at the MP2/6-311+G(2d,p) level by scanning through the dihedral angles of the two functional groups and the carbon-carbon bond with the remaining nuclear coordinates being energy-minimized. It was found that the potentials could be represented by the direct-bond potentials between the adjacent molecular fragments and by the through-space electrostatic potentials between the vicinal and geminal fragments. Here, the through-direct-bond potentials are represented by the conventional three Fourier terms of the internal rotation angles, and the through-space potentials, which include the intramolecular hydrogen bonding between X and Y, are represented by the general functional forms of the electric dipole-dipole, dipole-quadrupole, and quadrupole-quadrupole interaction terms. The fitted electrostatic interaction strengths between the X and Y fragments are in good agreement with the predictions of the theoretical molecular fragment dipole and quadrupole moments calculated by the Hirshfeld charge population analysis. Under the present energy decomposition scheme, the intrinsic gauche interactions, which are free of the contribution of the intramolecular H-bonding, could be obtained and correlated with the group electronegativities of X and Y. The potentials were also calculated by the MM3 molecular mechanics method and compared with the present results. With the global conformation potentials, the thermodynamic functions of the molecules and also their individual conformers are calculated and compared with the gas-phase experimental thermodynamic data in the literature.
AB - The global conformational potentials of 1,2-ethanediol, 1,2-ethanediamine, and 2-aminoethanol (X-CH2-CH2-Y; X, Y = OH or NH2) were obtained at the MP2/6-311+G(2d,p) level by scanning through the dihedral angles of the two functional groups and the carbon-carbon bond with the remaining nuclear coordinates being energy-minimized. It was found that the potentials could be represented by the direct-bond potentials between the adjacent molecular fragments and by the through-space electrostatic potentials between the vicinal and geminal fragments. Here, the through-direct-bond potentials are represented by the conventional three Fourier terms of the internal rotation angles, and the through-space potentials, which include the intramolecular hydrogen bonding between X and Y, are represented by the general functional forms of the electric dipole-dipole, dipole-quadrupole, and quadrupole-quadrupole interaction terms. The fitted electrostatic interaction strengths between the X and Y fragments are in good agreement with the predictions of the theoretical molecular fragment dipole and quadrupole moments calculated by the Hirshfeld charge population analysis. Under the present energy decomposition scheme, the intrinsic gauche interactions, which are free of the contribution of the intramolecular H-bonding, could be obtained and correlated with the group electronegativities of X and Y. The potentials were also calculated by the MM3 molecular mechanics method and compared with the present results. With the global conformation potentials, the thermodynamic functions of the molecules and also their individual conformers are calculated and compared with the gas-phase experimental thermodynamic data in the literature.
UR - http://www.scopus.com/inward/record.url?scp=0031207660&partnerID=8YFLogxK
U2 - 10.1021/jp971022j
DO - 10.1021/jp971022j
M3 - Article
AN - SCOPUS:0031207660
SN - 1089-5639
VL - 101
SP - 6107
EP - 6117
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 34
ER -