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(organic chemistry)
C6H4(OH)2 White 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.



(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.


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.

References in periodicals archive ?
If using 4% hydroquinone to treat melasma, results can take up to 20 weeks.
Kelly emphasized that hydroquinone should not be used in pregnant women.
While exogenous ochronosis is seen in about 42% of South African women and 15% of South African men using hydroquinone, the condition is very rare in the United States.
This should enhance the urinary concentration of free hydroquinones released from arbutin and thereby increase the antiseptic effect of these teas or phytopharmaceutical drug preparations.
After centrifugation of the samples and separation of the bacteria from the supernatant a 20 fold higher amount of free hydroquinones was detected in the bacterial sediments as compared to the supernatant (Table 3, Fig.