1,4-Benzoquinone

1,4-Benzoquinone, commonly known as para-quinone, is a chemical compound with the formula C₆H₄O₂. In a pure state, it forms bright-yellow crystals with a characteristic irritating odor, resembling that of chlorine, bleach, and hot plastic. This six-membered ring compound is the oxidized derivative of 1,4-hydroquinone. The molecule is multifunctional: it exhibits properties of a ketone, forming an oxime; an oxidant, forming the dihydroxy derivative; and an alkene, undergoing addition reactions, especially those typical for α,β-unsaturated ketones. 1,4-Benzoquinone is sensitive toward both strong mineral acids and alkali, which cause condensation and decomposition of the compound.

Preparation

Industrial routes

1,4-Benzoquinone is prepared by oxidation of diisopropylbenzene via a reaction related to the Hock rearrangement:

The reaction proceeds via the bis(hydroperoxide). Acetone is a coproduct.

Another major process involves the direct hydroxylation of phenol by acidic hydrogen peroxide: C₆H₅OH + H₂O₂ → C₆H₄(OH)₂ + H₂O Both hydroquinone and catechol are produced. Subsequent oxidation of the hydroquinone gives the quinone.