User`s guide

7. Exercises
View the output and click
New Job Using This Geometry. Run a Gaussian Bond Order
calculation at the same level of theory, which performs a NBO (Natural Bonding Orbital) analysis
of the Bond Order. Starting with the same same geometry, run a Gamess Molecular Energy UHF
(Unrestricted Hartree-Fock) 3-21G calculation of this doublet molecule. Finally, starting with the
same geometry, run a Mopac Geometry Optimization job at the PM3 level of theory.
If time permits, run a Gaussian Calculation = “AIM=BondOrders” job at the same level of theory.
Be patient since AIM jobs take a relatively long time! View the Raw Output to obtain the AIM
bond orders.
Construct a table with columns for NBO, GAMESS, MOPAC, and AIM, and rows for each unique
bond order and a row for calculation time. Comment on your table.
J. Isodesmic Reactions
28. Isodesmic Reaction Analysis of CO
2
Heat of Formation
Build and perform Geometry Optimization and Vibrational Frequencies (or Optimize+Vib Freq)
calculations on carbon dioxide (CO
2
), formaldehyde (H
2
CO), and methane (CH
4
) at the Hartree-
Fock 6-31G(d) level. Tabulate the energy (0 K) and enthalpy (298 K) for each.
Use these results to calculate
∆
rxn
H for
CO
2
+ CH
4
→ 2 H
2
CO
Explain why this reaction is an isodesmic reaction. Explain what kind of computational results
can be expected for such reactions.
Combine your
∆
rxn
H result with the experimental heats of formation for methane and
formaldehyde to predict the heat of formation for carbon dioxide. Compare your predicted heat of
formation with the experimental value. Experimental heats of formation may be obtained from the
NIST Chemistry Webbook (http://webbook.nist.gov/chemistry).
K. IRC Scans
29. Intrinsic Reaction Coordinate Verification of the H
2
CO → H
2
+ CO
Transition State
Compute the H
2
CO → H
2
+ CO transition state by building the following planar structure:
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