CHF3 Molecular Orbital Calculations

Trifluoromethane Molecular Orbital Calculations

The Highest Occupied Molecular Orbital (HOMO) for trifluoromethane (CHF₃) was determined using the Double Zeta Valence (DZV) level of theory.

The Lowest Unoccupied Molecular Orbital (LUMO) for CHF₃was based off of DZV calculations.

Th electrostatic potential of CHF₃ was mapped; red represents high electrons density and blue represents low electron density.

The partial atomic charges for carbon, hydrogen, and fluorine in CHF₃ were determined based on the DZV level of theory.

The bond lengths and bond angles for CHF₃ were determined based on the DZV geometry optimization.

The DZV level of theory was chosen for this molecule because it determined the most accurate bond lengths and bond angles.

Table 1: Experimental and literature values for bond lengths and angles for CHF₃.¹

Bond	Bond Length (Å)	Bond Angle (º)
C-H	1.098±0.008	---------------------
C-F	1.332±0.008	108.8

An IR spectrum for CHF₃ can be seen by following the link below.
CHF3 IR Spectrum

Table 2: The wavenumbers and the corresponding bending and/or stretching that occurs at the significant peaks on the IR spectra above.²

Wavenumber (1/cm)	Bond and Motion
~1150	C-F stretching
~1400	Csp3-bending
~3050	Csp3-H stretching

These different modes of vibration can be seen by clicking the buttons below.

This shows the bending of the bond between carbon and fluorine.

The following animation depicts the bending and stretching of the bond between carbon and fluorine.

The bending of the bond between carbon and hydrogen is shown by clicking on the button below.

The following animation shows the stretching that occurs at the bond between carbon and hydrogen.

Table 3: The dipole moments of CHF₃ at the different levels of theory.¹

Level of Theory	Dipole Moment (D)
AM1	2.079345
6-31G	2.372354
6-21G	2.106802
DZV	2.554768
Theoretical	1.651

The best calculated value was the result of the AM1 calculation. The smaller basis set allowed for a lower value, which was closer to the theoretical value, although it still was not very accurate.

REFERENCES:
1. Lide, D. R. CRC Handbook of Chemistry and Physics; CRC Press: Boca Raton, 1992.
2. NIST: National Institute of Standards and Technology. http://webbook.nist.gov/cgi/cbook.cgi?ID=C75467&Units=SI&Mask=80#IR-Spec (accessed Mar 3, 2013).

Based on template by A. Herráez as modified by J. Gutow

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