Aromatic
compounds
Aromatic compounds

Aromatic compounds are compounds which
contain a benzene ring in their molecules
Aromatic hydrocarbons

Benzene C6H6

Methylbenzene C7H8

Ethylbenzene C8H10
Benzene
Benzene molecule

The six carbon-carbon bonds in benzene are
identical, intermediate in length between
double and single bonds
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.
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
Methylbenzene
Ethylbenzene
Physical properties



Physical state: Benzene. methylbenzene and
ethylbenzene are liquids
Insoluble in water
Soluble in non-polar solvents such as
cyclohexane
Uses

Methylbenzene is used as an industrial
solvent
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
Aromatic acid-base indicators

The acid-base indicators phenolphthalein
and methyl orange are also aromatic
compounds
Phenolphthalein
Methyl orange
Aromatic compounds and cancer

Some aromatic compounds are carcinogenic,
e.g. Benzene

However, not all aromatic compounds are
carcinogenic; aspirin is an example