Propanoic acid is a clear, colorless liquid with a pungent odor. It is also commonly referred to as propionic acid or ethylformic acid. Propanoic acid is a carboxylic acid that occurs naturally in certain foods, including milk, cheese, and bread. It is also used in food preservation and as a chemical intermediate in the production of pharmaceuticals, pesticides, and plastics. Other synonyms for propanoic acid include methylacetic acid, ethylcarboxylic acid, and propylformic acid. The chemical formula for propanoic acid is C3H6O2, and it has a molecular weight of 74.08 g/mol.