Benzene and Pyridine Exhibit Different Electrophilic Chemistry

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 Save.

When execution has completed, double click on the line "density potential..." . You can go between benzene and pyridine using the on and 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.