Propane12diols

Propane-1,2-diols, commonly called propylene glycol, is an organic compound with the formula C3H8O2. It is a vicinal diol derived from propane by replacing two adjacent hydrogens on C1 and C2 with hydroxyl groups. The molecule exists as two enantiomers, and commercial samples are typically a racemic mixture. It is a colorless, odorless, viscous liquid at room temperature and is highly miscible with water and many organic solvents. Its physical properties include a boiling point of 188.2°C and a melting point of −59°C; it is hygroscopic.

Industrial production occurs mainly by catalytic hydration of propylene oxide, yielding propylene glycol after reaction with water. Alternative routes include fermentation-derived processes or purification from glycerol-based streams. It is relatively low in acute toxicity and is widely used as a solvent and humectant.

In food, cosmetics, and pharmaceuticals, propanediol serves as a solvent, humectant, and carrier fluid; it also functions as an additive to retain moisture. It is used as a vehicle for flavors and fragrances and as a base for some injectable and topical formulations. In industry, it is used as an antifreeze agent and heat-transfer fluid.

Propylene glycol is generally recognized as safe (GRAS) for intended food uses and is approved for many cosmetic and pharmaceutical applications. It is metabolized in the body to lactate and pyruvate and is considered of low toxicity, but high doses can cause osmotic imbalance, lactic acidosis, or adverse effects in individuals with certain metabolic conditions or impaired elimination. It is not listed as a carcinogen.