User`s guide

7. Exercises
CC
H
HH
NH
H
CC
H
HH
NH
H
planar
pyramidal
For planar vinyl amine, adjust the hybridization of N to sp
2
and then clean up the geometry. Be
sure to adjust the dihedral of the amine group appropriately for each molecule. For each
conformation, optimize the geometry and calculate vibrational frequencies with a PM3 (or
Hartree-Fock 6-31G(d) or better) calculation.
Make a table with columns for conformation, energy, and type of stationary point. Characterize
each stationary point as a minimum or transition state using the frequency results.
Provide a picture of the vibrational mode corresponding to the reaction coordinate for inversion
about the nitrogen atom.
16. Stretching Frequencies of Carbonyl Groups
Calculate the C=O stretching frequency of formamide, acetaldehyde and acetyl chloride.
C
O
H
2
NH
C
O
H
3
CH
C
O
H
3
CCl
formamide
acetaldehyde acetyl chloride
(1740 cm
-1
) (1746 cm
-1
) (1822 cm
-1
)
Perform Optimize Geometry and Vibrational Frequencies (or Optimize+Vib Freq) Hartree-Fock
3-21G calculations for each molecule. Computed vibrational frequencies are systematically high
and are routinely scaled to better match experiment. The scaling factor for Hartree-Fock 3-21G
calculations is 0.9085. Make a table with columns for molecule, calculated CO stretch frequency,
scaled CO stretch frequency, and experimental frequency (indicated above).
Comment on the absolute and relative accuracy of frequency calculations.
17. Transition State for 1,3 Hydrogen Shift of Fluoropropene
Build the transition state for the 1,3 hydrogen shift of fluoropropene.
77