glycol

Glycol is a common name for a class of chemical compounds known as glycols or diols, characterized by having two hydroxyl (-OH) groups in the molecule. The best-known members are vicinal diols such as ethylene glycol (1,2-ethanediol) and propylene glycol (1,2-propanediol). The term can also refer to related diols with more carbon atoms.

Glycols are typically colorless liquids at room temperature, miscible with water, and highly hygroscopic due to the hydroxyl groups. They generally have relatively high boiling points for simple alcohols and are used as antifreeze, heat-transfer fluids, and solvents. Ethylene glycol is produced by hydration of ethylene oxide, while propylene glycol is made by hydration of propylene oxide; other glycols are produced from related epoxides or by oxidation of diols.

Applications are diverse: antifreeze and coolants for automotive and industrial systems; production of polyesters such as polyethylene terephthalate via reaction with terephthalic acid; solvents for paints, inks, and cleaners; humectants and carries in cosmetics, foods, and pharmaceuticals; and intermediates in chemical synthesis.

Safety and environment: ethylene glycol is toxic if ingested, metabolized to glycolic and oxalic acids, which can cause acidosis and organ damage; treatment includes fomepizole or ethanol and, in severe cases, dialysis. Propylene glycol is less toxic and widely used in food and pharmaceutical products. Glycols are generally biodegradable but can pose hazards to aquatic life at high concentrations and require proper handling and spill response.