What Is the Common Name for Propanoic Acid?
The common, widely used name for propanoic acid is propionic acid. The term propionic comes from the Greek words protos, meaning first, and pion, meaning fat, because propionic acid was one of the smallest fatty acids known to form soaps and salts. In most commercial, industrial, and food-related contexts, the compound is referred to as propionic acid. Its IUPAC name, propanoic acid, is preferred in formal scientific literature and education, where systematic naming conventions are followed.
Chemical Identity and Properties
Propanoic acid is a saturated carboxylic acid with the molecular formula C3H6O2 and a molecular weight of 74.08 grams per mole. Its CAS number is 79-09-4. The compound is an oily, clear, colorless liquid at room temperature with a density of 0.993 grams per cubic centimeter at 20 degrees Celsius. It boils at 141 degrees Celsius, melts at about minus 20.7 degrees Celsius, and has a refractive index of 1.387 at 20 degrees Celsius. Propanoic acid is volatile and has a strong, pungent odor that is easy to detect even at very low concentrations.
Chemical Behavior
Propanoic acid exhibits the typical behavior of carboxylic acids. It is a weak acid that partially dissociates in water to release hydrogen ions. It reacts with alcohols to form esters, a reaction known as esterification, and it can be reduced to propanol through hydrogenation processes. The carboxyl group at the end of the three-carbon chain is the reactive center, enabling the production of esters, salts, and acyl derivatives that are used across the chemical industry.
Preservative and Industrial Applications
Propionic acid and its salts, including calcium propionate and sodium propionate, are widely used as preservatives. Because propionic acid inhibits the growth of mold and certain bacteria, it is added to baked goods, animal feed, and silage to extend shelf life and prevent spoilage. In the European Union and many other regions, propionic acid is approved as a food preservative under the additive code E280. It is one of the few preservatives that is both effective against fungi and compatible with food production.
Beyond preservation, propionic acid is used as an intermediate in the production of herbicides and pharmaceuticals. It is also used to manufacture cellulose acetate propionate, a thermoplastic used in films, coatings, and molded articles. Propionic acid esters serve as solvents and flavoring agents, and the acid itself is used in the production of plasticizers, rubber chemicals, and dyes. The combination of moderate acidity, low toxicity, and good reactivity makes it a versatile building block in organic synthesis.
Handling and Safety
Propanoic acid is corrosive to skin and eyes and should be handled with protective equipment. Its vapor can irritate the respiratory tract, and concentrated material requires careful storage in corrosion-resistant containers. Because it is volatile, work areas should be ventilated. In dilute form, propionic acid is safely used in food products, but industrial handling demands the same precautions as for other carboxylic acids, including awareness of its flammability at elevated temperatures.
Frequently Asked Questions
What is the common name for propanoic acid? The common name is propionic acid, derived from Greek words meaning first and fat, reflecting its status as one of the smallest fatty acids.
What is the CAS number of propionic acid? The CAS number of propionic acid is 79-09-4 and its molecular formula is C3H6O2.
Is propionic acid the same as propanoic acid? Yes. They are the same compound; propanoic acid is the IUPAC systematic name and propionic acid is the common name.
What is propionic acid used for? It is used as a food and feed preservative, as an intermediate for herbicides and pharmaceuticals, and in the production of cellulose acetate propionate and esters.
Is propionic acid a weak or strong acid? Propionic acid is a weak acid that partially dissociates in water, like other carboxylic acids of its class.
What are the physical properties of propionic acid? It is a colorless oily liquid with a boiling point of 141 degrees Celsius, a melting point of about minus 20.7 degrees Celsius, and a density of 0.993 grams per cubic centimeter.