CAMBRIDGE INTERNATIONAL A2 LEVEL CHEMISTRY (9701) ORGANIC CHEMISTRY NOTES

CAMBRIDGE
INTERNATIONAL A2
LEVEL CHEMISTRY
(9701) ORGANIC
CHEMISTRY NOTES

, CHAPTER 25: BENZENE AND DERIVATIVES

Recap: AS organic chemistry:
- Electrophilic addition
- Nucleophilic substitution




Naming aromatic compounds:




Shape and bonding in benzene, C6H6:
- Shape:
o Carbon atoms are sp2 hybridized
o C-C-C bond angle of 120 – trigonal planar
o Benzene molecule has a planar structure
- Bonding:
o Sp2 orbitals between C-H and C-C overlap to form 3 σ bonds per C atom
o P orbitals from each carbon atom overlap sideways with each other forming π bonds
o The π bonds contain delocalized electrons  resonance structures



Resonance structures in benzene:

, Properties of benzene:
- Clear, colourless, non-polar liquid at r.t.p
- Volatile and has a low b.p.
- Relatively unreactive due to strong bonding
o Catalyst and/ or heating required



Reactions involving benzene and its derivatives:
- Electrophilic substitution
o Halogenation
 A hydrogen atom on an organic compound is replaced with one halogen group




o Alkylation
 Hydrogen atom on an organic compound is replaced with one alkyl group




o Acylation
 A hydrogen atom on an organic compound is replaced with one acyl group




o Nitration
 A hydrogen atom on an organic compound is replaced with one nitro (-NO 2)
group