• Benzene is an organic compound with the formula C6H6.
  • It’s a planar molecule consisting of a ring of six carbon atoms, each of which is also bonded to a hydrogen atom.
  • Benzene’s structure can be represented as a hexagon with a circle inside it to denote the pi system of electrons.

Structure and Stability

  • Benzene’s stability and unique properties are attributed to its resonating structure or delocalised model.
  • The six pi electrons are shared equally among the carbon atoms, creating a system of delocalised electrons above and below the plane of the molecule.
  • This delocalisation leads to extraordinary stability, a phenomenon referred to as aromatic stability.

Chemical Reactions

  • Benzene tends to undergo substitution reactions rather than addition, preserving its aromatic system which accounts for its stability.
  • For example, in nitration of benzene, a nitro group (-NO2) replaces one of the hydrogen atoms in the benzene ring.
  • Benzene can also undergo halogenation (the substitution of hydrogen with a halogen), sulfonation (the addition of a sulfonic acid group), and alkylation (the addition of an alkyl group) among other reactions.

Use of Benzene in Dyes

  • Benzene and its derivatives are vital for the synthesis of many dyes.
  • Azo dyes, for instance, often involve coupling reactions with benzene derivatives.
  • Importantly, the extended delocalisation of pi electrons in benzene rings is responsible for the colour properties of many organic compounds.

Health and Safety

  • Although benzene is a useful compound in chemistry, it’s recognised as a carcinogen and may cause health issues
  • Therefore, handling benzene demands utmost care, usage of personal protective equipment and good ventilation.

Key Points for Understanding Benzene

  • The resonance or delocalised model of benzene accounts for its unusual stability and reaction behaviour.
  • Substitution reactions are predominant in benzene due to its attempt to maintain aromatic stability.
  • Benzene’s conjugated pi system is essential to the colour properties of many organic compounds and dyes.
  • Handling benzene requires stringent safety precautions due to its carcinogenic nature.