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Phenoxyacetic acid

Phenoxyacetic acid, POA, is a white solid with the formula of C8H8O3.[1][2] 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.[3]

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.[2] 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.[1][4]

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.[5][6]

References

  1. ^ a b Wishart, David S.; Guo, An Chi; Oler, Eponine; Wang, Fel; Anjum, Afia; Peters, Harrison; Dizon, Raynard; Sayeeda, Zinat; Tian, Siyang; Lee, Brian L.; Berjanskii, Mark; Mah, Robert; Yamamoto, Mai; Jovel Castillo, Juan; Torres Calzada, Claudia; Hiebert Giesbrecht, Mickel; Lui, Vicki W.; Varshavi, Dorna; Varshavi, Dorsa; Allen, Dana; Arndt, David; Khetarpal, Nitya; Sivakumaran, Aadhavya; Harford, Karxena; Sanford, Selena; Yee, Kristen; Cao, Xuan; Budinsky, Zachary; Liigand, Jaanus; Zhang, Lun; Zheng, Jiamin; Mandal, Rupasri; Karu, Naama; Dambrova, Maija; Schiöth, Helgi B.; Gautam, Vasuk. "Showing metabocard for Phenoxyacetic acid (HMDB0031609)". Human Metabolome Database, HMDB. 5.0.
  2. ^ a b "Phenoxyacetic acid". Sigmaaldrich. 2021. Retrieved 2021-02-17.
  3. ^ "Phenoxyacetic Acid". Journal of the Chemical Society, Abstracts. 38: 318–319. 1880. doi:10.1039/CA8803800307.
  4. ^ Freed, V. H.; Chiou, C. T.; Schmedding, D.; Kohnert, R. (1979). "Some physical factors in toxicological assessment tests". Environmental Health Perspectives. 30: 75–80. Bibcode:1979EnvHP..30...75F. doi:10.1289/ehp.793075. PMC 1637710. PMID 446460.
  5. ^ "Phenoxyacetic acid". The Good Scents Company. Retrieved 2021-02-17.
  6. ^ "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". EFSA Journal. 5 (5). 2007. doi:10.2903/j.efsa.2007.417.