1. Aromatic compounds

2. Aromatic compounds
Aromatic compounds are compounds which contain a benzene ring in their molecules

3. Aromatic hydrocarbons
Benzene C6H6
Methylbenzene C7H8
Ethylbenzene C8H10

4. Benzene

5. Benzene molecule
The six carbon-carbon bonds in benzene are identical, intermediate in length between double and single bonds

6. Sigma bonding in benzene
Six carbon atoms joined to form a hexagonal planar ring.
Each carbon has four valence electrons
One of these is used to form a bond with a hydrogen atom.
Two other electrons are used to form sigma bonds with the carbon atoms on either side.

7. What the circle means
The 6 valence electrons not involved in sigma bonding are shared between the six carbon atoms in the molecule
not localised into 3 double bonds
For convenience the C and H atoms are not shown
Ring in centre indicates a delocalised pi bond

8. Methylbenzene

9. Ethylbenzene

10. Physical properties
Physical state: Benzene. methylbenzene and ethylbenzene are liquids
Insoluble in water
Soluble in non-polar solvents such as cyclohexane

11. Uses
Methylbenzene is used as an industrial solvent

12. Range and scope of aromatic chemistry
Pharmaceutical compounds, e.g. Morphine
Herbicides, e.g. Diuron
Detergents, e.g. Sodium dodecylbenzenesulfonate
Dyes, e.g. Martius Yellow

13. Aromatic acid-base indicators
The acid-base indicators phenolphthalein and methyl orange are also aromatic compounds
Phenolphthalein Methyl orange

14. Aromatic compounds and cancer
Some aromatic compounds are carcinogenic, e.g. Benzene
However, not all aromatic compounds are carcinogenic; aspirin is an example