CH3CH2COOH

Propanoic acid, commonly called propionic acid, is an organic carboxylic acid with the formula CH3CH2COOH. It consists of a three-carbon chain bearing a terminal carboxyl group (IUPAC name: propanoic acid).

It is a colorless, oily liquid with a distinctive sharp odor. It is miscible with water and many organic solvents. It is a weak acid, with a pKa of about 4.87 at 25°C, and a boiling point near 141°C. The compound is hygroscopic and can be corrosive in concentrated form.

Propionic acid occurs in nature in small amounts in dairy products and is produced by certain bacteria during fermentation. Industrially, it is produced by oxidation of propionaldehyde or via hydroformylation of ethylene to propionaldehyde followed by oxidation. It forms salts such as sodium propionate and calcium propionate, which are widely used as food preservatives.

Major uses include food preservation, particularly in bread, where propionate salts inhibit mold growth. It is a versatile building block in organic synthesis and a precursor to esters used in flavors and fragrances.

Chemically, propanoic acid undergoes typical carboxylic acid reactions: it reacts with bases to form propionate salts, and with alcohols to form propanoate esters. It can be reduced to propionaldehyde and further to propanol under suitable conditions.

Safety: propionic acid is corrosive and an irritant to skin, eyes, and the respiratory tract. It should be handled with appropriate protective equipment and stored away from bases and oxidizers.