4-Hydroxybenzoic acid
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Rifleman 82
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{{Chembox new
| Name = 4-Hydroxybenzoic acid
| ImageFile = 4-Hydroxybenzoic acid.svg
| ImageSize = 75px
| ImageName = 4-Hydroxybenzoic acid
| IUPACName = 4-Hydroxybenzoic acid
| OtherNames = ''p''-Hydroxybenzoic acid<br />''para''-Hydroxybenzoic acid
| Section1 = {{Chembox Identifiers
| CASNo = 99-96-7
| SMILES = OC1=CC=C(C(O)=O)C=C1
| PubChem = 135
}}
| Section2 = {{Chembox Properties
| Formula = C<sub>7</sub>H<sub>6</sub>O<sub>3</sub>
| MolarMass = 138.12074 g/mol
| Density = 1.46 g/cm³
| MeltingPt = 214-217 °C
}}
}}
'''4-Hydroxybenzoic acid''', or ''p''-hydroxybenzoic acid, is a [[phenol]]ic derivative of [[benzoic acid]]. It is a white crystalline solid that is slightly soluble in water and [[chloroform]], but soluble to extremely soluble in [[alcohol]]s, [[diethyl ether|ether]], and [[acetone]].
4-Hydroxybenzoic acid is primarily known as the basis for the preparation of its [[ester]]s, known as [[paraben]]s, which are used as preservatives in cosmetics.
==Production==
4-Hydroxybenzoic acid is produced commercially from potassium [[phenol|phenoxide]] and [[carbon dioxide]] in the [[Kolbe-Schmitt reaction]]. It can also be produced in the laboratory by heating [[salicylic acid|potassium salicylate]] with [[potassium carbonate]] to 240 °C, followed by treating with acid.<ref>[[Organic Syntheses]], [http://www.orgsyn.org/orgsyn/pdfs/CV2P0341.pdf p-hydroxybenzoic acid], Coll. Vol. 2, p. 341 (1943).</ref>
==See also==
The closely related 2-hydroxybenzoic acid is known as [[salicylic acid]], a precursor to [[aspirin]].
==References==
{{reflist}}
{{DEFAULTSORT:Hydroxybenzoic acid, 4-}}
[[Category:Phenols]]
[[Category:Benzoic acids]]
[[Category:Monomers]]
[[Category:Hydroxy acids]]
{{phenol-stub}}