propanoaatsiionien

Propanoate ions are the conjugate bases of propionic acid, with the formula C3H5O2−. They arise when propionic acid loses a proton. The negative charge is delocalized over the two oxygen atoms by resonance, giving two major resonance structures. The pKa of propionic acid is about 4.87, so at neutral pH the propanoate anion predominates.

They occur as salts with various cations, such as sodium propionate, potassium propionate, calcium propionate, and ammonium propanoate, commonly obtained by neutralizing propionic acid with the corresponding base. In solution, propanoate acts as a weak base and can participate in acid–base equilibria depending on the pH of the medium.

Propanoate salts are generally soluble in water; sodium and potassium propionates are highly soluble, while calcium propionate is less soluble. They are used as food preservatives and antifungal agents, particularly calcium propionate in bread and bakery products, and sodium propionate in dairy and meat products. They also serve as buffering agents in some formulations.

Biochemically, propionate is involved in metabolism: it is converted to propionyl-CoA and then to methylmalonyl-CoA, subsequently forming succinyl-CoA to enter the citric acid cycle. Propionate can be produced by gut microbiota from certain dietary substrates and amino acids, contributing to the body's propanoate pool under specific conditions.

Safety and regulation: Many propanoate salts are approved as food additives with established acceptable daily intakes; excessive intake may cause gastrointestinal symptoms in sensitive individuals.