Propylene Glycol

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Propylene glycol, also called 1,2-propanediol or propane-1,2-diol, is an organic compound (a diol or double alcohol) with formula C3H8O2 or HO-CH2-CHOH-CH3. It is a colorless, nearly odorless, clear, viscous liquid with a faintly sweet taste, hygroscopic and miscible with water, acetone, and chloroform. The compound is sometimes called ¿-propylene glycol to distinguish it from the isomer propane-1,3-diol HO-(CH2)3-OH, also called ß-propylene glycol. Propylene glycol contains an asymmetrical carbon atom, so it exists in two stereoisomers. The commercial product is a racemic mixture. Pure optical isomers can be obtained by hydration of optically pure propylene oxide. Industrially propylene glycol is produced from propylene oxide. Different manufacturers use either non-catalytic high-temperature process at 200 °C (392 °F) to 220 °C (428 °F), or a catalytic method, which proceeds at 150 °C (302 °F) to 180 °C (356 °F) in the presence of ion exchange resin or a small amount of sulfuric acid or alkali.