Hydroquinone

hydroquinone [¦hī·drə·kwə′nōn]

(organic chemistry)

C₆H₄(OH)₂White crystals melting at 170°C and boiling at 285°C; soluble in alcohol, ether, and water; used in photographic dye chemicals, in medicine, as an antioxidant and inhibitor, and in paints, varnishes, and motor fuels and oils. Also known as hydrochinone; hydroquinol; quinol.

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Hydroquinone 

(also called p-dihydroxy-benzene), colorless crystals. Melting point, 170.3° C; density, 1.358 g/cm³. Sublimates in a vacuum.

Hydroquinone is readily soluble in ethanol and ether and slightly soluble in benzene; 5.7 g of hydroquinone dissolves in 100 g of water at 15° C. It is a powerful reducing agent. In aqueous solutions, particularly alkaline solutions, it is oxidized by atmospheric oxygen.

p-benzoquinone

Hydroquinone is produced industrially by the reduction of quinone, as well as by alkaline fusion of p -hydroxy-benzenesulfonic acid or p -chlorophenol.

Hydroquinone is used as a photographic developer and as an antioxidant. It is an intermediate in the synthesis of many organic dyes. In analytical chemistry it is used in the determination of a number of elements. The molecular compound of hydroquinone with quinone—so-called quinhydrone, C₆H₄O₂ C₆H₄(OH)₂—is used in determining hydrogen-ion concentration. The compound of hydroquinone with glucose, arbutin, is widespread in nature. Hydroquinone was first prepared by the German chemist F. Wöhler in 1844.