Summary
Highlights
Benzene is an organic chemical compound with the formula C6H6, classified as a hydrocarbon due to its composition of only carbon and hydrogen atoms. It is a common aromatic hydrocarbon, naturally found in crude oil and used as a component in gasoline due to its high octane number. Benzene is a colorless, highly flammable liquid with a sweet smell, contributing to the aroma around petrol stations. Substituted benzene and polybenzenes are known as aryls.
Benzene was first isolated by Michael Faraday in 1825 from the oily residue of illuminating gas production. In 1836, August Laurent proposed it be called 'phene'.
The empirical formula of benzene, C6H6, was known, but its highly unsaturated structure made determining its full structure challenging. Many scientists proposed structures with double bonds or rings, but Friedrich Kekulé was the first to deduce the ring structure in a dream. While Kekulé's model with alternating pi bonds was a breakthrough, it could not explain why all carbon-carbon bonds are of the same length; this was later explained by electron delocalization. Therefore, benzene is represented by a hexagon with a circle in the center, symbolizing delocalized electrons.
Benzene is a colorless, flammable liquid with a sweet, gasoline-like odor. It is non-polar, making it immiscible in water but soluble in organic solvents. It is a toxic chemical and a carcinogen, meaning continuous exposure can cause cancer.
Benzene primarily undergoes electrophilic substitution reactions, despite its high degree of unsaturation. Addition reactions are not preferred as they cause a loss of aromaticity, but can occur under extreme conditions, such as hydrogenation at 475-500 Kelvin with a catalyst. Like other hydrocarbons, benzene combusts to form carbon dioxide and water, burning with a sooty flame due to its high carbon content.
Benzene is a significant component in the manufacturing of tires and rubber. It is also used as a solvent in strong adhesives, such as those used for attaching shoe soles.