polyhydric

Polyhydric is an adjective used in chemistry to describe molecules that contain more than one hydroxyl (-OH) group. The term is most often applied to polyhydric alcohols, also called polyols, which include dihydric, trihydric, and higher-hydric compounds. The presence of multiple hydroxyl groups makes these substances highly polar, increases hydrogen bonding, and generally enhances water solubility. In practice, polyhydric compounds include diols such as glycols, as well as trihydric and higher polyols, including glycerol and many sugar alcohols.

In common usage, polyhydric compounds encompass substances with two or more hydroxyls, including glycerol (propane-1,2,3-triol), sorbitol, xylitol, and related molecules. They are valued for their chemical reactivity, stability, and properties as humectants, solvents, sweeteners, and plasticizers. In polymer chemistry, polyols serve as building blocks and crosslinkers for polyurethane and related polymers. In biology and biochemistry, polyhydric compounds participate in metabolic pathways, such as glycerol-derived intermediates in lipid metabolism.

Notes on terminology: the term polyhydric appears more frequently in older or more formal literature. Modern nomenclature often uses polyol or polyhydroxy compound to describe molecules with multiple hydroxyl groups. Safety and physiological effects vary among polyhydric compounds; many are relatively non-toxic, but certain polyols can cause laxative effects or osmotic imbalances at high intakes.