What Is Propionic Acid?
Propionic acid, a 3-carbon saturated fatty acid, is a clear, colorless liquid with a characteristic odor.
Also known as propanoic acid, it dissolves readily in water, ethanol, and acetone. Propionic acid is produced through the hydrolysis of propionitrile or the oxidation of 1-propanol.
It is designated as a Class 4 hazardous substance due to its toxic properties, including mucous membrane irritation and corrosiveness. Naturally occurring as a microorganism metabolite, propionic acid is present in fermented foods like miso, soy sauce, and cheese.
Uses of Propionic Acid
As a carboxylic acid, propionic acid (CH3CH2COOH) finds wide industrial use in pharmaceuticals, herbicides, fragrances, and resins, and serves as a preservative by inhibiting mold and bacterial growth.
1. Use in Organic Synthesis
Valued as a solvent, dissolution aid, and esterifier, propionic acid contributes to the production of polymers, plastics, and non-steroidal anti-inflammatory drugs (NSAIDs).
2. Use in Flavoring
Propionic acid’s unique odor lends itself to fruit flavorings, such as ethyl propionate, which imparts a pineapple-like aroma and is utilized in food flavoring.
3. Antimicrobial Activity and Fungicide Use
Known for its antimicrobial properties, particularly in cheese, propionic acid is employed as a food additive to prevent mold growth in cheese, bread, and confectionery, and as a pH adjuster, shampoo additive, and livestock feed additive.
Properties of Propionic Acid
Propionic acid has a molecular formula of C3H6O2, a molecular weight of 74.08 g/mol, melting point of -20.83°C, and is highly soluble in water, ethanol, chloroform, and ether.
Structure of Propionic Acid
Propionic acid, with its linear carboxylic acid structure, is soluble in water and exhibits low reactivity towards oxidation, reduction, and thermal decomposition. It is flammable when mixed with strong oxidizers and its vapor can be irritating.
Other Information on Propionic Acid
Production Methods
Primarily synthesized chemically, propionic acid is often a byproduct of other compounds’ synthesis, notably acetic acid production from naphtha oxidation. Direct synthesis from n-propanol, propionaldehyde, or hydrolysis of propiononitrile is less common. Fermentation using propionibacterium freudenreichii, or propionic acid bacteria, represents an alternative method.