Propanoic acid is a naturally-occurring carboxylic acid with chemical formula CH₃CH₂COOH. This chemical is a kind of bulk pharmaceutical chemical. There are some basic informations about this crude drug: (1)CAS No.: ; (2)PubChem: 1032; (3)ChemSpider: 1005; (4)Molecular formula: C₃H₆O₂; (5)Molar mass: 74.08 g/mol; (6)Appearance: colourless liquid; (7)Solubility in water: miscible.

Propanoic acid has physical properties intermediate between those of the smaller carboxylic acids, formic and acetic acids, and the larger fatty acids. It is miscible with water, but can be removed from water by adding salt.

In industry, propanoic acid is mainly produced by the hydrocarboxylation of ethylene using nickel carbonyl as the catalyst:

H₂C=CH₂ + H₂O + CO → CH₃CH₂CO₂H

It is also produced by the aerobic oxidation of propionaldehyde. In the presence of cobalt or manganese ions, this reaction proceeds rapidly at temperatures as mild as 40–50 °C:

CH₃CH₂CHO + 1/2O₂ → CH₃CH₂COOH.

Propanoic acid inhibits the growth of mold and some bacteria at the levels between 0.1 and 1% by weight. As a result, most propanoic acid produced is consumed as a preservative for both animal feed and food for human consumption. For animal feed, it is used either directly or as its ammonium salt.

Propanoic acid is also useful as an intermediate in the production of other chemicals, especially polymers. -acetate-propionate is a useful thermoplastic. Vinyl propionate is also used. In more specialized applications, it is also used to make pesticides and pharmaceuticals. The esters of propanoic acid have fruit-like odors and are sometimes used as solvents or artificial flavorings.