Betahydroxy

Betahydroxy is a term used in organic chemistry to describe a hydroxyl group positioned on the beta carbon of a carbon chain relative to a reference functional group, such as a carboxyl or carbonyl group. The beta (β) position is the second carbon away from the functional group, so a β-hydroxy designation indicates the presence of an –OH group on that carbon. In practice, betahydroxy is commonly encountered in names such as beta-hydroxy acids and beta-hydroxy ketones, and it is often written with the Greek letter β or spelled out as beta-hydroxy.

The concept is most familiar in the context of beta-hydroxy acids, where the hydroxyl-bearing carbon is three atoms away from the carboxyl carbon (for example, 3-hydroxypropionic acid, also called β-hydroxypropionic acid). Beta-hydroxybutyric acid (3-hydroxybutanoic acid) is another well-known example, contributing to metabolic pathways as a ketone body when reduced or oxidized in physiological conditions. Beta-hydroxylated compounds can arise through enzymatic beta-hydroxylation, chemical hydration of beta-keto derivatives, or other synthetic routes.

Nomenclature notes: betahydroxy is sometimes written as beta-hydroxy or β-hydroxy, reflecting the position of the hydroxyl group relative to the functional group. The descriptor helps distinguish isomers that differ only in the position of the hydroxyl group along the carbon chain. See also hydroxy groups, beta-hydroxy acids, and beta-hydroxy ketones.