Benzene is a cyclic hydrocarbon with a chemical formula C6H6, that is, each carbon atom in benzene is arranged in a six-membered ring and is bonded to only one hydrogen atom. According to molecular orbital theory for benzene structure, benzene ring involves the formation of three delocalized π – orbitals spanning all six carbon atoms, while the valence bond theory describes two stable resonance structures for the ring.
Benzene is one of the most fundamental compounds used in the manufacturing of various plastics, resins, synthetic fibres, rubber lubricants, dyes, detergents, drugs, and pesticides. Naturally, benzene is produced through volcanoes and forest fires. There are various laboratories and industrial techniques existing for the preparation of benzene. Commercially, benzene is chiefly obtained from coal tar. Some laboratory techniques for the preparation of benzene are discussed below:
Preparation of benzene from alkynes
Benzene is prepared from ethyne by the process of cyclic polymerization. In this process, Ethyne is passed through a red-hot iron tube at 873 K. The ethyne molecule then undergoes cyclic polymerization to form benzene.
Preparation of benzene from aromatic acids
Benzene can be prepared from aromatic acids through decarboxylation reaction. In this process, the sodium salt of the benzoic acid (sodium benzoate) is heated with soda lime to produce benzene along with sodium carbonate.
Preparation of benzene from phenol
Benzene can be prepared from phenols too through their reduction. In this process vapours of phenol are passed over heated zinc dust. Zinc dust reduces them to form benzene.
Preparation of benzene from sulphonic acids
Benzene can be prepared from sulphonic acids through their hydrolysis. In this process Benzene sulphonic acid is exposed to superheated steam leading to the formation of benzene.
C6H5-SO3H + H2O → C6H6 + H2SO4
These were some basic methods for the laboratory preparation of benzene. To learn about other processes for the commercial and laboratory preparation of benzene download BYJU’S – The Learning App.