User`s guide

7. Exercises
Cl F
F
F
Cl
F
F
F
Cl F
F
F
planar
tee
pyramidal
To build a particular geometry, construct ClF
5
, set the hybridization of the central Cl atom to dsp3
with the Adjust tool by control-clicking on Cl, choose Clean-Up: Geometry (not
Comprehensive!), and finally delete the undesired F atoms.
If a particular geometry optimization calculation fails to converge, click the Restart button in Job
Manager, and view the last computed geometry. If this conformation is different than the initial
geometry, what does this mean about the stability of the initial geometry?
Construct a table with columns for initial geometry and optimized energy. Explain whether or not
your results agree with VSEPR (Valence Shell Electron Pair Repulsion) theory learned in General
Chemistry.
Optionally, verify that PM3 Geometry Optimizations give a different result.
10. Conformers of Vinyl Alcohol
Build vinyl alcohol-0°, vinyl alcohol-180°, acetaldehyde-0°, and acetaldehyde-60°.
CC
H
H
H
O
H
vinyl alcohol-0°
CC
H
H
H
OH
vinyl alcohol-180°
CC
HH
O
H
H
CC
H
OH
H
H
acetaldehyde-0°
acetaldehyde-60°
Perform a Geometry Optimization Hartree-Fock 3-21G calculation on each.
If using WebMO Pro, select the four jobs in Job Manager and click the Spreadsheet button to
obtain an immediate comparison among the four calculations. Otherwise, view the results of each
job.
Make a table with columns for molecule, number of optimization steps, energy (Hartree), relative
energy (kcal/mol). The relative energy should be calculated relative to the global minimum. 1
Hartree = 627.5095 kcal/mol.
74