Preparation of Benzene - Aromatic compounds in Organic Chemistry

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:

Table of Contents

• • • Preparation of benzene from alkynes
    • Preparation of benzene from aromatic acids
    • Preparation of benzene from phenol
    • Preparation of benzene from sulphonic acids

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.