Phenoxyacetic acid, POA, is a white solid with the formula of C₈H₈O₃. Although not itself usefully

active Active may refer to: Music * ''Active'' (album), a 1992 album by Casiopea * Active Records, a record label Ships * ''Active'' (ship), several commercial ships by that name * HMS ''Active'', the name of various ships of the British Royal ...

as an herbicide, it forms the part-structure of many

phenoxy herbicide Phenoxy herbicides (or "phenoxies") are two families of chemicals that have been developed as commercially important herbicides, widely used in agriculture. They share the part structure of phenoxyacetic acid. Auxins The first group to be discover ...

derivatives including

MCPA MCPA (2-methyl-4-chlorophenoxyacetic acid) is a powerful, selective, widely used phenoxy herbicide. The pure compound is a brown-colored powder. MCPA has been extensively used in agriculture to control broad-leaf weeds as a growth regulator prima ...

and 2,4-D.

Structure and synthesis

Phenoxyacetic acid is an ''O''-phenyl derivative of

glycolic acid Glycolic acid (or hydroxyacetic acid; chemical formula HOCH2CO2H) is a colorless, odorless and hygroscopic crystalline solid, highly soluble in water. It is used in various skin-care products. Glycolic acid is widespread in nature. A glycolate ( ...

. It is both a monocarboxylic acid and an aryl ether. Its preparation from

sodium phenolate Sodium phenoxide (sodium phenolate) is an organic compound with the formula NaOC6H5. It is a white crystalline solid. Its anion, phenoxide, also known as phenolate, is the conjugate base of phenol. It is used as a precursor to many other organic ...

and

sodium chloroacetate Sodium chloroacetate is the organic compound with the formula CH2ClCO2Na. A white, water-soluble solid, it is the sodium salt of chloroacetic acid. Many of its uses are similar to those of the parent acid. It is prepared by treating chloroacetic ...

in hot water was first reported in 1880. :1) C₆H₅O⁻Na⁺ + ClCH₂COO⁻Na⁺ → C₆H₅OCH₂COO⁻Na⁺ + NaCl :2) C₆H₅OCH₂COO⁻Na⁺ + HCl → C₆H₅OCH₂COOH + NaCl The phenolate

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

reacts via

nucleophilic attack In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they a ...

on the

methylene Methylene may refer to: * Methylene group or methylene bridge (CH2< or equivalently -CH2-), a part of a molecule connected to the rest of the molecule by two single bonds. * An older name for methylidene (=CH2), a part of a molecule connected t ...

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 Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a h ...

diethyl ether Diethyl ether, or simply ether, is an organic compound in the ether class with the formula , sometimes abbreviated as (see Pseudoelement symbols). It is a colourless, highly volatile, sweet-smelling ("ethereal odour"), extremely flammable liq ...

and

benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen ato ...

. Phenoxyacetic acid is a weak acid and weak base with a pKa of 3.7.

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.

References

{{Reflist Phenoxyacetic acids