en>Friend of facts2: /* Unit weights */ Add link to Wikipedia article on robust regression

2014-02-03T20:42:38Z

Unit weights: Add link to Wikipedia article on robust regression

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{{chembox
| Watchedfields = changed
| verifiedrevid = 477222223
| Name = 4-Hydroxybenzoic acid
| ImageFileL1 = 4-Hydroxybenzoic acid.svg
| ImageSizeL1 = 95px
| ImageNameL1 = Skeletal formula
| ImageFileR1 = 4-Hydroxybenzoic-acid-3D-balls.png
| ImageSizeR1 = 108px
| ImageNameR1 = Ball-and-stick model
| IUPACName = 4-Hydroxybenzoic acid
| OtherNames = ''p''-Hydroxybenzoic acid ''para''-Hydroxybenzoic acid
| Section1 = {{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 132
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = C00156
| InChI = 1/C7H6O3/c8-6-3-1-5(2-4-6)7(9)10/h1-4,8H,(H,9,10)
| InChIKey = FJKROLUGYXJWQN-UHFFFAOYAQ
| SMILES1 = c1cc(ccc1C(=O)O)O
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 441343
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C7H6O3/c8-6-3-1-5(2-4-6)7(9)10/h1-4,8H,(H,9,10)
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = FJKROLUGYXJWQN-UHFFFAOYSA-N
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 99-96-7
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 30763
| DrugBank_Ref = {{drugbankcite|correct|drugbank}}
| DrugBank = DB04242
| SMILES = O=C(O)c1ccc(O)cc1
| PubChem = 135
| EINECS = 202-804-9
}}
| Section2 = {{Chembox Properties
| Formula = C7H6O3
| MolarMass = 138.121 g/mol
| Appearance = white crystalline
| Odor = odorless
| Density = 1.46 g/cm³
| MeltingPtC = 214.5
| Solubility = 0.5 g/100 mL
| SolubleOther = soluble in [[alcohol]], [[ether]], [[acetone]] slightly soluble in [[chloroform]] negligible in [[carbon disulfide|CS2]]
| pKa = 4.54
| LogP = 1.58
}}
| Section5 = {{Chembox Hazards
| MainHazards = Irritant
| ExternalMSDS = [http://www.hmdb.ca/system/metabolites/msds/000/000/419/original/HMDB00500.pdf?1358461253 HMDB]
| AutoignitionC = 250
| NFPA-H = 2 | NFPA-F = 0 | NFPA-R = 0
| LD50 = 2200 mg/kg (oral, mouse)
}}
}}

'''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 [[alcohol]]s 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 and some ophthalmic solutions. It is [[isomer]]ic with 2-hydroxybenzoic acid, known as [[salicylic acid]], a precursor to [[aspirin]].

== Natural occurrences ==
''[[Cryptanaerobacter phenolicus]]'' is a bacterium species that produces [[benzoic acid|benzoate]] from [[phenol]] via 4-hydroxybenzoate.<ref name=Juteau>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}}</ref>

[[p-Hydroxybenzoic acid glucoside]] can be found in mycorrhizal and non-mycorrhizal roots of Norway spruces (''[[Picea abies]]'').<ref>Phenolics of mycorrhizas and non-mycorrhizal roots of Norway spruce. Babette Münzenberger, Jürgen Heilemann, Dieter Strack, Ingrid Kottke and Franz Oberwinkler, Planta, Volume 182, Number 1, pages 142-148, {{doi|10.1007/BF00239996}}</ref>

[[Violdelphin]] is ananthocyanin, a type of plant pigments, found in blue flowers and incorporating two p-hydroxy benzoic acid residues, one rutinoside and two glucosides associated with a [[delphinidin]].

=== Occurrences in food ===
4-Hydroxybenzoic acid can be found naturally in ''[[Cocos nucifera]]''.<ref>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}}</ref> It is one of the main catechins [[metabolite]]s found in humans after consumption of [[green tea]] infusions.<ref>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}}</ref> It is also found in [[wine]]<ref>Comparison of Phenolic Acids and Flavan-3-ols During Wine Fermentation of Grapes with Different Harvest Times. Rong-Rong Tian, Qiu-Hong Pan, Ji-Cheng Zhan, Jing-Ming Li, Si-Bao Wan, Qing-Hua Zhang and Wei-Dong Huang, Molecules, 2009, 14, pages 827-838, {{doi|10.3390/molecules14020827}}</ref> and in vanilla.

[[Açaí oil]], obtained from the fruit of the [[açaí palm]] (''Euterpe oleracea''), is rich in p-hydroxybenzoic acid (892 ± 52 mg/kg).<ref>{{cite journal |journal = J Agric Food Chem |date=Jun 2008 | volume = 56 | issue = 12 | pages = 4631–6 | title = Chemical composition, antioxidant properties, and thermal stability of a phytochemical enriched oil from Acai (Euterpe oleracea Mart.) | authors = Pacheco-Palencia LA, Mertens-Talcott S, Talcott ST |PMID = 18522407| doi = 10.1021/jf800161u}}</ref>

== Chemical production ==
4-Hydroxybenzoic acid is produced commercially from potassium [[phenol|phenoxide]] and [[carbon dioxide]] in the [[Kolbe-Schmitt reaction]].<ref>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}}</ref> 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>{{OrgSynth | prep = CV2P0341 | author = C. A. Buehler and W. E. Cate | title = ''p''-Hydroxybenzoic acid | collvol = 2 | collvolpages = 341 | year = 1943 }}</ref>

== Chemical reactions ==
4-Hydroxybenzoic acid has about one tenth the acidity of [[benzoic acid]], having an [[acid dissociation constant]] ''Ka'' = 3.3 x 10−5 M at 19 °C.{{cn|date=August 2012}} Its acid dissociation follows this equation:
:HOC6H4CO2H <math>\overrightarrow{\leftarrow}</math> HOC6H4CO2− + H+

== Safety ==
4-Hydroxybenzoic acid is a popular antioxidant in part because of its low toxicity. The {{LD50}} is 2200 mg/kg in mice (oral).{{cn|date=August 2012}}

== References ==
{{reflist}}

{{Phenolic acid}}

{{DEFAULTSORT:Hydroxybenzoic acid, 4-}}
[[Category:Monomers]]
[[Category:Monohydroxybenzoic acids]]
[[Category:Phenolic human metabolites]]

Unit-weighted regression - Revision history

en>Friend of facts2: /* Unit weights */ Add link to Wikipedia article on robust regression