Aromatic chemistry
spec
bonding
The nature of the bonding in a benzene ring limited to planar structure and
bond length intermediate between
single and double.
Delocalisation of p electrons makes benzene more stable than the
theoretical molecule cyclohexa-1,3,5-triene.
Students should be able to:
• use thermochemical evidence from enthalpies of
hydrogenation to account for this extra stability
• explain why substitution reactions occur in preference to
addition reactions.
Electrophilic substitution
Electrophilic attack on benzene rings results in substitution, limited to
monosubstitutions.
Nitration is an important step in synthesis, including the manufacture of
explosives and formation of amines.
Friedel–Crafts acylation reactions are also important steps in synthesis.
Students should be able to outline the electrophilic substitution mechanisms
of:
• nitration, including the generation of the nitronium ion
• acylation using AlCl3
as a catalyst
Benzene stability
benzene is more stable than the theoretical alternative cyclohexa-1,3,5-triene (the
alternate single and double bond model)
measure the stability of benzene by comparing the enthalpy change of
hydrogenation in benzene and cyclo-1,3,5-triene
Aromatic chemistry 1
spec
bonding
The nature of the bonding in a benzene ring limited to planar structure and
bond length intermediate between
single and double.
Delocalisation of p electrons makes benzene more stable than the
theoretical molecule cyclohexa-1,3,5-triene.
Students should be able to:
• use thermochemical evidence from enthalpies of
hydrogenation to account for this extra stability
• explain why substitution reactions occur in preference to
addition reactions.
Electrophilic substitution
Electrophilic attack on benzene rings results in substitution, limited to
monosubstitutions.
Nitration is an important step in synthesis, including the manufacture of
explosives and formation of amines.
Friedel–Crafts acylation reactions are also important steps in synthesis.
Students should be able to outline the electrophilic substitution mechanisms
of:
• nitration, including the generation of the nitronium ion
• acylation using AlCl3
as a catalyst
Benzene stability
benzene is more stable than the theoretical alternative cyclohexa-1,3,5-triene (the
alternate single and double bond model)
measure the stability of benzene by comparing the enthalpy change of
hydrogenation in benzene and cyclo-1,3,5-triene
Aromatic chemistry 1
