Quantum Calculations for Fluoride, H2CS, and Benzoic Acid
Kaitlyn Harsla and Ross Denholm
Introduction
Quantum mechanics is a powerful tool for gaining insight into
particular forces that govern molecular interactions and atomic
relationships. The immensely complex calculations made in these
computer programs would take a team of chemists months to decipher,
allowing one to make assertions about molecular phenomena with
confidence. Wavefunctions for electrons are represented in these
visual aids by colorful, bulbous molecular orbitals. This enables
an onlooker the ability to visualize what these calculations are
outlining. The wavefunctions created using different levels of
theory provide a variety of perspectives on the particular behavior on
an atomic scale. The larger the data set, more factors taken into
account offer a clearer the picture of what is happening in molecules.
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Depiction of the highest occupied molecular orbitals (HOMO) of fluoride.
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In order to find the HOMO of F2, Gamess
quantum calculator determined that fluoride's ninth orbital domain,
which was determined to be the highest energy orbital occupied by
at
least one electron due to valence considerations.
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Valence energy level diagram for F2. The highest occupied molecular orbital is 2p pi antibonding. The lowest unoccupied is the 2p sigma antibonding orbital.
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The lowest unoccupied molecular orbital of the F2 molecule, orbital ten, pictured above.
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Pictured is a model of the lowest
unoccupied molecular orbital of the fluoride molecule. It is one
energy level higher than that of the highest energy orbital occupied by
electrons.
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Electronic Potential vs. Bond Length
As atoms approach one another potential energy drops due to the
stabilizing effect chemical bonding has on molecules. 8+ angstroms
essentially demonstrates two atoms at infinite distance, where around
-200 Hartrees represents the zero energy of nonbonded atoms.
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The highest
occupied molecular orbital
of
H2CS; orbital 12.
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This disjointed array of orbitals represents the grouping containing the highest energy electrons of H2CS.
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H2CS model of the lowest unoccupied molecular orbitals.
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The picture illustrates the shape of the 13th orbital shell of H2CS, its lowest unoccupied shell.
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Charge separation of H2CS
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Molecular model of H 2CS, including
separation of charges between the individual atoms. Due to the
existence of partial charges, this molecule is considered polar.
| Dipole Moments of H2CS and Benzoic Acid
H2CS
Level of Theory Dipole Moment (in Debeyes)
AMI
2.119675
DZV
2.154723
PM3
2.074266
621-G
2.447574
631-G
2.572209
Benzoic Acid
Level of Theory Dipole Moment (in Debeyes)
AMI
2.417831
DZV
2.492621
PM3
2.252452
621-G
1.998134
631-G
2.446429
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Benzoic acid highest occupied molecular orbital- orbital 61.
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HOMO of benzoic acid. Its 61st orbital shell, containing the electrons of highest energy.
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Depiction of the lowest unoccupied orbital shell of benzoic acid.
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Layout of the lowest energy orbital pattern for benzoic acid that is unoccupied by electrons.
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Infrared Spectrum of Benzoic Acid
Spectrum website: http://sdbs.db.aist.go.jp/sdbs/cgi-bin/direct_frame_top.cgi
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CLICK IMAGE TO
ACTIVATE 3D
Insert a caption for BenzoicBondLength here. |
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Bond length comparison between literature and experimental values for benzoic acid.
Bond Literature Value (Angsr) Experimental Value (Angst)
O=C
1.22
1.22
O-C 1.36
1.36
C-C
1.48
1.40
C-C(arom.) 1.39
1.39
O-H
0.95
0.96
C-H
1.09
1.07
Bond Angle Literature (Deg) Experimental (Deg)_______
C-C=C
119.9
120.6
C-O-H
85.0
85.0
C-C-H
121.2
119.5
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Based on template by A.
Herráez as modified by J. Gutow
Page skeleton
and JavaScript generated by export to web function using Jmol 14.2.15_2015.07.09
2015-07-09 22:22 on Feb 29, 2016.The bond
length between carbon bonds varies slightly due to the high
electronegativity of chlorine present
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