MO calculations by Z. Chambers and Gage Kerscher

Introduction


Several molecular orbital calculations were performed for hydrofluoric acid, nitrogen dioxide, and 2-chlorobiphenyl. Additionally, electronic transition energies were calculated for 2-chlorobiphenyl. The calculations were preformed using various levels of theory: semi-empirical (AM1 and PM3), and ab initio (6-21G, 6-31G, and Double Zeta Valence). The Double Zeta Valence (DZV) yielded the structural properties for all three molecules with the lowest energy expectation values.

The following table lists the number of AO's and MO's found for each molecule using ab initio theory.

Molecular and Atomic Orbital Calculations

The next table contains experimentally derived dipole moments at each level of theory. Experimental values obtained from NIST: HF - 1.820, NO2 - 0.316, 2-cholorobiphenyl - 1.43.
Debye data



IR Spectra

NO2 (obtained from organicchem.org) The largest peak around 1580 inverse centimeters corresponds to symmetric stretching.


2-chlorobiphenyl (obtained from NIST). The peak near 1600 inverse centimeters is due to C-C stretching and the one near C-H is due to C-H stretching.

The following graphs illustrate the potential energy of bond stretching for HF at different levels of theory. The first graph shows how far off AM1, the smallest basis set was from the others. The second graph shows that as the size of the basis set increases, the calculated potential energy decreases.







 Follow these links for results and discussion for each molecule:

Results on HF, NO2, and and 2-chlorobiphenyl.