1. Aromatic
compounds

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

3. Aromatic hydrocarbons
 Benzene
C6H6
 Methylbenzene
 Ethylbenzene
C7H8
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
solvent
is used as an industrial

12. Range and scope of aromatic
chemistry
 Pharmaceutical
 Herbicides,
compounds, e.g. Morphine
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