Benzene and Pyridine Exhibit Different
Electrostatic potential maps
are used to point out vast differences in the "electrophilic chemistry"
of benzene and pyridine.
Build benzene and pyridine. Click on .
Click on the Rings button (in the model kit), select Benzene
from the menu and click anywhere on screen. Click on .
Select New Molecule from the File menu. Benzene
(Rings menu) is still selected, so click anywhere on screen.
Select aromatic nitrogen
from the model kit and double click on one of the carbon atoms
(not a free valence). Click on
and then click on .
Select Calculations from the Setup menu and specify calculation
of equilibrium geometry using the Hartree-Fock 3-21G model. Click
on OK. Select Surfaces from the Setup menu. Click
on Add at the bottom of the dialog and select density from
the Surface menu and potential from the Property menu.
Click on OK. Select Submit from the Setup menu,
supply the name "benzene and pyridine" and click on
When execution has completed, double click on the line "density
potential..." . You can go between benzene and pyridine using the
keys at the bottom left of the screen.
The "red" regions in benzene, which are most attractive to
an electrophile, correspond to the molecule's system, while in pyridine
they correspond to the s system in the vicinity of the nitrogen.