4-Hydroxybenzoic acid
| 4-Hydroxybenzoic acid | |
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4-Hydroxybenzoic acid |
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Other names
p-Hydroxybenzoic acid |
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| Identifiers | |
| CAS number | 99-96-7  |
| PubChem | 135 |
| ChemSpider | 132 |
| DrugBank | DB04242 |
| KEGG | C00156 |
| ChEBI | CHEBI:30763 |
| ChEMBL | CHEMBL441343 |
| Jmol-3D images | Image 1 Image 2 |
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| Properties | |
| Molecular formula | C7H6O3 |
| Molar mass | 138.12 g/mol |
| Density | 1.46 g/cm³ |
| Melting point |
214–217 °C |
 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
4-Hydroxybenzoic acid is a monohydroxybenzoic acid, a phenolic derivative of benzoic acid. It is a white crystalline solid that is slightly soluble in water and chloroform but more soluble in polar organic solvents such as alcohols and acetone. 4-Hydroxybenzoic acid is primarily known as the basis for the preparation of its esters, known as parabens, which are used as preservatives in cosmetics and some ophthalmic solutions. It is isomeric with 2-hydroxybenzoic acid, known as salicylic acid, a precursor to aspirin.
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[edit] Natural occurrence
4-Hydroxybenzoic acid can be found naturally in Cocos nucifera.[1] It is one of the main catechins metabolites found in humans after consumption of green tea infusions.[2]
Açaí oil, obtained from the fruit of the açaí Palm (Euterpe oleracea), is rich in p-hydroxybenzoic acid (892 ± 52 mg/kg), protocatechuic acid (630 ± 36 mg/kg) and ferulic acid (101 ± 5.9 mg/kg).[3]
Cryptanaerobacter phenolicus is a bacterium species that produces benzoate from phenol via 4-hydroxybenzoate.[4]
[edit] Chemical production
4-Hydroxybenzoic acid is produced commercially from potassium phenoxide and carbon dioxide in the Kolbe-Schmitt reaction.[5]
4-Hydroxybenzoic acid can also be produced in the laboratory by heating potassium salicylate with potassium carbonate to 240 °C, followed by treating with acid.[6]
[edit] Chemical reactions
It is about 10x less acidic than benzoic acid, Ka = 3.3 x 10−5 M at 19 °C:
- HOC6H4CO2H
HOC6H4CO2− + H+
HOC6H4CO2− + H+[edit] Safety
4-Hydroxybenzoic acid is popular antioxidant in part because of its low toxicity. The LD50 is 2200 mg/kg in mice (oral).
[edit] References
- ^ Profiling C6–C3 and C6–C1 phenolic metabolites in Cocos nucifera. Gargi Dey, Moumita Chakraborty and Adinpunya Mitra, Journal of Plant Physiology, Volume 162, Issue 4, 22 April 2005, Pages 375-381 doi:10.1016/j.jplph.2004.08.006
- ^ Catechin metabolites after intake of green tea infusions. P. G. Pietta, P. Simonetti, C. Gardana, A. Brusamolino, P. Morazzoni and E. Bombardelli, BioFactors, 1998, Volume 8, Issue 1-2, pp. 111–118, doi:10.1002/biof.5520080119
- ^ Pacheco-Palencia LA, Mertens-Talcott S, Talcott ST (Jun 2008). "Chemical composition, antioxidant properties, and thermal stability of a phytochemical enriched oil from Acai (Euterpe oleracea Mart.)". J Agric Food Chem 56 (12): 4631–6. doi:10.1021/jf800161u. PMID 18522407.
- ^ Cryptanaerobacter phenolicus gen. nov., sp. nov., an anaerobe that transforms phenol into benzoate via 4-hydroxybenzoate. Pierre Juteau, Valérie Côté, Marie-France Duckett, Réjean Beaudet, François Lépine, Richard Villemur and Jean-Guy Bisaillon, IJSEM, January 2005, vol. 55, no. 1, pages 245-250, doi:10.1099/ijs.0.02914-0
- ^ Edwin Ritzer and Rudolf Sundermann “Hydroxycarboxylic Acids, Aromatic” in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi: 10.1002/14356007.a13_519
- ^ C. A. Buehler and W. E. Cate (1943), "p-Hydroxybenzoic acid", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV2P0341; Coll. Vol. 2: 341
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