Polyhydric Alcohols

alcohols of the fatty series that contain several —OH groups in the molecule. Polyhydric alcohols, as well as other polyatomic compounds containing more than one functional group per molecule, are classified as dihydric (glycols), trihydric (glycerols), tetrahydric (tetritols), pentahydric (pentitols), hexahydric (hexitols), and so on. The most important alcohols that contain no fewer than four —OH groups are pentaerythritol, C(CH₂OH)₄, and the pentitols (for example, xylitol, adonitol, and arabitol) and hexites (mannitol, sorbitol, and dulcitol), which are genetically related to monosaccharides.

Polyhydric alcohols are colorless crystalline substances with a sweet taste that are readily soluble in water. Many of them are synthesized in plants. A large number of stereoisomers are known to exist for each type of alcohol. Polyhydric alcohols exhibit all the properties characteristic of monohydric alcohols (for example, they readily undergo esterification and oxidation). Nitrates of polyhydric alcohols are explosive.

Polyhydric alcohols are usually prepared commercially by the reduction of aldoses and ketoses. They are used in the manufacture of polymers (pentaerythritol and xylitol) and explosives, and also as sugar substitutes for diabetics (sorbitol and xylitol). They are also used as moistening agents in the manufacture of cosmetics and pharmaceuticals; their ethers are used as emulsifiers.