Quantum chemical treatment of β-sitosterol molecule

Figures & data

Figure 1.  Ball and stick model with labels of optimized structure of the β-sitosterol molecule. Red: oxygen; dark gray: carbon; light gray: hydrogen (PM3 result).

Figure 2.  Bond lengths between carbon atoms in β-sitosterol molecule; hydrogen atoms are not displayed (PM3 result).

Table 1.  Energy contributions (in kcal/mol) after molecular mechanics (MM) method with MM+ force field.

Contribution	Value
Bond	3.766
Angle	11.258
Dihedral	28.137
vdW	17.822
Stretch-bend	0.904
Electrostatic	0.286
Total	62.172

Note. vdW, van der Waals.

Table 2.  Calculated energies (in kcal/mol) after PM3 method.

Quantity	Value
Total energy	−100,434.922
Binding energy	−7469.436
Isolated atomic energy	−92,965.486
Electronic energy	−1,031,581.063
Core–core interaction	931,146.141
Heat of formation	−124.061

Figure 3.  Calculated infrared spectrum of β-sitosterol molecule (PM3 result).

Figure 4.  Directions of vibrations in β-sitosterol molecule (PM3 result).

Table 3.  The first 16 relatively larger infrared intensities (in km/mol) and the corresponding harmonic frequencies (in cm⁻¹) after PM3 method.

Intensity	Frequency	Intensity	Frequency
22.71248	367.28	3.43942	1096.41
11.23686	374.00	2.91183	1382.75
7.50335	3071.15	2.61672	600.37
4.87831	1263.91	2.54071	1303.08
4.63438	379.77	2.27232	1343.91
4.62016	1401.09	2.23868	1369.92
3.89302	1403.20	2.23294	877.27
3.83999	1404.16	2.21367	1030.10

Table 4.  Some of the calculated quantities after DFT/B3LYP/6-31G* method.

Quantity	Value
Total energy (Hartree)	−1170.769
Electronic kinetic energy (Hartree)	1164.929
eN energy (Hartree)	−8618.648
Nuclear repulsion energy (Hartree)	2952.109
Highest MO (Hartree)	2.559
LUMO (Hartree)	0.022
HOMO (Hartree)	−0.227
Lowest MO (Hartree)	−19.126
HOMO–LUMO difference, Eg (eV)	6.775
Dipole moment, µ (debye)	2.487
Virial (–V/T)	2.005

Note. LUMO, lowest unoccupied molecular orbital; HOMO, highest occupied molecular orbital.

Figure 5.  3D images of highest occupied molecular orbital (HOMO, upper) and lowest unoccupied molecular orbital (LUMO, lower) of β-sitosterol molecule (DFT/6-31G* results).

Figure 6.  Excess (Mulliken) charge on atoms of β-sitosterol molecule (DFT/6-31G* result).

Figure 7.  3D images of charge density (upper) and electrostatic potential (lower) of β-sitosterol molecule (DFT/6-31G* results).