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| Hydroquinone | |
|---|---|
| General | |
| Systematic name | Hydroquinone |
| Other names | Quinol Benzene-1,4-diol |
| Molecular formula | C6H4(OH)2 |
| SMILES | OC1=CC=C(O)C=C1 |
| Molar mass | 110.1 g/mol |
| Appearance | white solid |
| CAS number | * |
| Properties | |
| Density and phase | 1.3 g/cm3, solid |
| Solubility in water | 5.9 g/100 ml (15 °C) |
| Melting point | 172 °C |
| Boiling point | 287 °C |
| Acidity (pKa) | ? |
| Dipole moment | zero |
| Hazards | |
| MSDS | External MSDS |
| EU classification | Harmful (Xn) Carc. Cat. 3 Muta. Cat. 3 Dangerous for the environment (N) |
| NFPA 704 | |
| R-phrases | , , , , , |
| S-phrases | , , , |
| Flash point | 165 °C |
| RTECS number | MX3500000 |
| Supplementary data page | |
| Structure and properties | n, εr, etc. |
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Related benzenediols | Pyrocatechol Resorcinol |
| Related compounds | 1,4-benzoquinone |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Chemical infobox | |
Hydroquinone, also benzene-1,4-diol, is an aromatic organic compound which is a type of phenol, having the chemical formula C6H4(OH)2. Its chemical structure, shown in the table at right, has two hydroxyl groups bonded to a benzene ring in a para position. It is a white granular solid at room temperature and pressure.
Nomenclature
Hydroquinone is the name recommended by the International Union of Pure and Applied Chemistry (IUPAC) in its 1993 Recommendations for the Nomenclature of Organic Chemistry.
Properties
Hydroquinone can undergo mild oxidation to convert to the compound parabenzoquinone, C6H4O2, often called p-quinone or simply quinone. Reduction of quinone reverses this reaction back to hydroquinone. Some biochemical compounds in nature have this sort of hydroquinone or quinone section in their structures, such as Coenzyme Q, and can undergo similar redox interconversions.
The hydroxyl groups of hydroquinone are quite weakly acidic. Hydroquinone can lose an H+ from one of the hydroxyls to form a monophenolate ion or lose an H+ from both to form a diphenolate ion.
Uses
Hydroquinone has a variety of uses principally associated with its action as a reducing agent which is soluble in water. It is a major component in most photographic developers where, with the compound Metol, it reduces silver halides to elemental silver.
In human medicine, hydroquinone has been used as a topical application to reduce the color of skin as it does not have the same predisposition to cause dermatitis as Metol does. This use is banned in some countries (e.g. France) because of fears of a cancer risk.
The disodium diphenolate salt of hydroquinone is used as an alternating comonomer unit in the production of the polymer PEEK.
See also
Reference
External links
- International Chemical Safety Card 0166
- NIOSH Pocket Guide to Chemical Hazards
- IARC Monograph: "Hydroquinone"
- IUPAC Nomenclature of Organic Chemistry (online version of the "Blue Book")
Benzenediols | Photographic chemicals | IARC Group 3 carcinogens
"Hydroquinone"