Chem3D Users Manual - CambridgeSoft

Administrator
Hyperfine Coupling Constants
H6 0.05672
H7 0.05479
Example 7
UHF Spin Density for the
Ethyl Radical
The Message window displays a list of atomic
orbital spin densities.
The atomic orbitals are not labeled for each
value, however, the general rule is shown in the
table below (MOPAC only uses s, p x , p y and p z
orbitals).
Atomic Orbital Spin Density
A.O.
0.07127 C1 s
0.06739 C1 p x
To calculate the UHF spin density:
1. Create the ethyl radical as described in “Spin
Density” on page 189.
0.08375 C1 p y
0.94768 C1 p z
-0.01511 C2 S
-0.06345 C2 p x
-0.01844 C2 p y
2. From the MOPAC Interface submenu of the
Calculations menu, choose Minimize
Energy.
3. On the Theory tab, select PM3.
4. On the Properties tab, select Open Shell
(Unrestricted) and Spin Density.
-0.03463 C2 p z
-0.07896 H3 s
0.07815 H4 s
0.01046 H5 s
0.05488 H6 s
0.05329 H7 s
You can reason from the result shown below that
the unpaired electron in the ethyl radical is more
localized at p z orbital on C1. Generally, this is a
good indication of the reactive site
196•MOPAC Computations
CambridgeSoft
Computing Properties