CHEM 2302 Lecture Notes

1-4-17

Ch.9

* Benzene and its Derivatives

C6H6 Not double – single – double – etc

Does not do alkene reactions

All C – C bonds are ~ 1.5 bonds



All C are sp2

All have p orbitals

Forms π bonds



O–O

C–C

O–O



*




Benzene Naphthalene Anthracene

,* Aromatic compounds

Aromaticity: unusual stability like benzene

Hacked: criteria for aromaticity

- Be a closed loop (ring)

- Every atom in the ring must have a p orbital

- Must be planar (flat) or nearly flat

- Must have 4n + 2 π electrons where n = 0, 1, 2, 3, etc (2, 6, 10, 14, etc)




Double bond = 2 π electrons 10 π e-

Total: 6 π e- Is aromatic

Is aromatic




4 π e-

Not aromatic 8 π e-

Not aromatic

,* H 6 π e- in loop



H H

H H

N not in loop

Pyridine




N N N

H H H

6 π e-

4 from double bond + 2 from lone pair

Is aromatic



*




O O O

In loop out loop 6 π e- in loop

, *



B B

H H

Empty p orbital 4 π e-

2 π e- Not aromatic

Is aromatic



*




H

Empty p orbital

2 π e-

Is aromatic




H

6 π e-

Is aromatic