phenoxyacetic acid
{{Chembox
| Name = Phenoxyacetic acid
| ImageFile = Phenoxyacetic-acid.png
| PIN = Phenoxyacetic acid
| OtherNames =
| Section1 = {{Chembox Identifiers
| CASNo = 122-59-8
| Beilstein = 907949
| ChEBI = 8075
| ChEMBL = 173521
| ChemSpiderID = 18107
| DTXSID = DTXSID9025873
| EINECS = 204-556-7
| Gmelin = 142730
| KEGG = C02181
| PubChem = 19188
| QID = Q904253
| UNNumber = 3347
| UNII = YRC253429Q
| StdInChI=1S/C8H8O3/c9-8(10)6-11-7-4-2-1-3-5-7/h1-5H,6H2,(H,9,10)
| StdInChIKey = LCPDWSOZIOUXRV-UHFFFAOYSA-N
| SMILES = C1=CC=C(C=C1)OCC(=O)O
}}
| Section2 = {{Chembox Properties
| C=8|H=8|O=3
| MolarMass = 152.15 g/mol
| Appearance = White solid or tan powder
| Odor = Sweet and sour
| MeltingPtC = 98 - 99
| pKa = 3.7
| LogP = 1.48
}}
| Section3 =
| Section4 =
| Section5 =
| Section6 = {{Chembox Hazards
| GHSPictograms = {{GHS07}}
| GHSSignalWord = Warning
| HPhrases = {{H-phrases|302|315|319|335}}
| PPhrases = {{P-phrases|261|264|270|271|280|301+312|302+352|304+340|305+351+338|312|321|330|332+313|337+313|362|403+233|405|501}}
}}
}}
Phenoxyacetic acid, POA, is a white solid with the formula of C8H8O3.{{Cite HMDB|author1-link=David S. Wishart|title=Showing metabocard for Phenoxyacetic acid (HMDB0031609)|url=https://hmdb.ca/metabolites/HMDB0031609}}{{Cite web|last=|first=|date=2021|title=Phenoxyacetic acid|url=https://www.sigmaaldrich.com/catalog/product/mm/800667?lang=en®ion=GB|archive-url=|archive-date=|access-date=2021-02-17|website=Sigmaaldrich}} Although not itself usefully active as an herbicide, it forms the part-structure of many phenoxy herbicide derivatives including MCPA and 2,4-D.
Structure and synthesis
Phenoxyacetic acid is an O-phenyl derivative of glycolic acid. It is both a monocarboxylic acid and an aryl ether. Its preparation from sodium phenolate and sodium chloroacetate in hot water was first reported in 1880.{{cite journal |doi=10.1039/CA8803800307 |doi-access= |title=Phenoxyacetic Acid |journal=Journal of the Chemical Society, Abstracts |year=1880 |volume=38 |pages=318–319 }}
:1) C6H5O−Na+ + ClCH2COO−Na+ → C6H5OCH2COO−Na+ + NaCl
:2) C6H5OCH2COO−Na+ + HCl → C6H5OCH2COOH + NaCl
The phenolate anion reacts via nucleophilic attack on the methylene carbon of the chloroacetic acid, forming an ether bond.
Properties
Phenoxyacetic acid is a white or clear crystalline compound at room temperature. When impure, it can appear to be a light tan to brown. The compound has a solubility in water of 12 g/L and is highly soluble in organic solvents including ethanol, diethyl ether and benzene. Phenoxyacetic acid is a weak acid and weak base with a pKa of 3.7.{{cite journal |doi=10.1289/ehp.793075 |title=Some physical factors in toxicological assessment tests |year=1979 |last1=Freed |first1=V. H. |last2=Chiou |first2=C. T. |last3=Schmedding |first3=D. |last4=Kohnert |first4=R. |journal=Environmental Health Perspectives |volume=30 |pages=75–80 |pmid=446460 |pmc=1637710 |bibcode=1979EnvHP..30...75F }}
Uses
Phenoxyacetic acid has found minor uses as a food additive and perfume component and is categorised as "generally recognised as safe" in these applications.{{cite web |url=http://www.thegoodscentscompany.com/data/rw1033781.html |title=Phenoxyacetic acid |website=The Good Scents Company |access-date=2021-02-17 }}{{cite journal |doi=10.2903/j.efsa.2007.417 |doi-access=free |title=Opinion of the Scientific Panel on food additives, flavourings, processing aids and materials in contact with food (AFC) related to Flavouring Group Evaluation 23 (FGE.23): Aliphatic, alicyclic and aromatic ethers including anisole derivatives from chemical groups 15, 16 and 26 (Commission Regulation (EC) No 1565/2000 of 18 July 2000 |journal=EFSA Journal |year=2007 |volume=5 |issue=5 }}
References
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