📘 Chapter 17 – Aromatic Compounds

Requirements for aromaticity

Fully conjugated + 4n+2 π electrons

Hückel's Rule

4n+2 π electrons

Aromatic compound

Fully conjugated + 4n+2 π electrons

Antiaromatic compound

Fully conjugated + 4n π electrons

Nonaromatic compound

Not fully conjugated

Good Hückel numbers

2, 6, 10, 14, 18...

Before counting π electrons...

Check if the ring is fully conjugated

Why is benzene unusually stable?

Aromatic electron delocalization

Ortho

1,2

Meta

1,3

Para

1,4

Benzylic position

Carbon directly attached to an aromatic ring

Benzylic oxidation reagents

KMnO4 or H2CrO4

Product of benzylic oxidation

Carboxylic acid

Requirement for benzylic oxidation

At least one benzylic hydrogen

Benzylic bromination reagents

NBS or Br2/hν

Birch reduction reagents

Na, NH3, ROH

Birch reduction product

1,4-cyclohexadiene

EDGs in Birch end up on

Sp3 carbon

EWGs in Birch end up on

Sp2 carbon

Aromatic 1H NMR

6.5–8 ppm

Aromatic 13C NMR

~100–150 ppm