Introduction: Aromatic Compounds
Halogenation Cl2/Br2 with AlCl3/AlBr3 catalyst Aryl Halide
Nitration Mixture of concentrated HNO3 and Nitroarene
concentrated H2SO4 at a temperature
between 25-60
Friedel-Crafts Halogenoalkane and anhydrous AlCl3 Alkylbenzne
Alkylation catalyst
Friedel-Crafts Acyl chloride and anhydrous AlCl3 catalyst Acylbenzene
Acetylation
Complete Hot alkaline KMnO4 and dilute acid Benzoic Acid
Oxidation
Hydrogenation Hydrogen and Pt/Ni catalyst and heat Cyclohexane
Structure of Benzene
Benzene has the formulae C6H6. It has a planar cyclic structure where 6 carbons are joined
together in a ring. Each carbon forms a single covalent bond to the carbons either side of it and
a hydrogen. The unpaired electrons of each carbon atoms are located in a p-orbital which stick
out above and below the plane of the ring. The p-orbitals on each carbon atom combine to form
a ring of delocalised electrons. They are delocalised because they do not belong to a specific
carbon.
The delocalised ring of electrons is replaced by a circle in the ring of the C-C bonds.
The term aromatic refers to molecules which contain one or more benzene rings - a ring
with conjugated pi systems.
Conjugated pi systems arise from alternative C=C and C-C bonds where electrons are
delocalised.
All the bonds in the ring are the same so they are all the same length of 140pm. This value
lies in between the length of a single bond 147pm and a double bond 135pm. This is
because the double and single bonds alternate.
Benzene is used in polymers, pharmaceuticals, dyes and pesticides. Common pain killers such
as aspirin, paracetamol all contain benzene rings.
Halogenation Cl2/Br2 with AlCl3/AlBr3 catalyst Aryl Halide
Nitration Mixture of concentrated HNO3 and Nitroarene
concentrated H2SO4 at a temperature
between 25-60
Friedel-Crafts Halogenoalkane and anhydrous AlCl3 Alkylbenzne
Alkylation catalyst
Friedel-Crafts Acyl chloride and anhydrous AlCl3 catalyst Acylbenzene
Acetylation
Complete Hot alkaline KMnO4 and dilute acid Benzoic Acid
Oxidation
Hydrogenation Hydrogen and Pt/Ni catalyst and heat Cyclohexane
Structure of Benzene
Benzene has the formulae C6H6. It has a planar cyclic structure where 6 carbons are joined
together in a ring. Each carbon forms a single covalent bond to the carbons either side of it and
a hydrogen. The unpaired electrons of each carbon atoms are located in a p-orbital which stick
out above and below the plane of the ring. The p-orbitals on each carbon atom combine to form
a ring of delocalised electrons. They are delocalised because they do not belong to a specific
carbon.
The delocalised ring of electrons is replaced by a circle in the ring of the C-C bonds.
The term aromatic refers to molecules which contain one or more benzene rings - a ring
with conjugated pi systems.
Conjugated pi systems arise from alternative C=C and C-C bonds where electrons are
delocalised.
All the bonds in the ring are the same so they are all the same length of 140pm. This value
lies in between the length of a single bond 147pm and a double bond 135pm. This is
because the double and single bonds alternate.
Benzene is used in polymers, pharmaceuticals, dyes and pesticides. Common pain killers such
as aspirin, paracetamol all contain benzene rings.
