Phenoxyacetic acid
Phenoxyacetic acid, POA, is a white solid with the formula of CHO. 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. 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. 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.