Arenes (Overview)

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Structure & Bonding

All C atoms in benzene are sp2 hybridised → benzene is planar π e– are delocalised within the benzene ring → (i) added stability due to charge dispersal and (ii) all C–C bonds in the ring have equal bond lengths non-polar simple molecular structures consisting of benzene molecules held together by weak VDW forces

Physical Properties

relatively low mp/bp insoluble in water; soluble in organic solvents (e.g. CCl4)

Chemical Properties

Benzenes have an e– rich region (cloud of delocalised e– above and below the planar ring) → react with electrophiles are unsaturated (contain C=C) but undergo substitution to preserve aromaticity (stability) → undergo electrophilic substitution reactions

Main Reaction(s)

Benzene Electrophilic substitution (with X+/ NO2+) Methylbenzene Electrophilic substitution (with X+/ NO2+) Free radical substitution (with X2) Side chain oxidation (with KMnO4)