3Hydroxyl

3-hydroxyl, or 3-hydroxy, refers to a hydroxyl group (-OH) attached to the third carbon atom of a molecule. In IUPAC naming, the prefix 3-hydroxy- indicates substitution at carbon 3, and the locants for other functional groups modify accordingly. The presence of a hydroxyl group at this position contributes to the molecule’s polarity and ability to form hydrogen bonds, often increasing solubility in water relative to nonpolar compounds.

In practice, 3-hydroxy can appear in a wide range of chemical contexts, including linear, branched, and cyclic structures. The stereochemistry of a 3-hydroxyl-bearing center depends on the surrounding framework; in cyclic systems, the hydroxyl can be oriented axial or equatorial, influencing reactivity and interaction with enzymes and receptors. In biochemistry and organic synthesis, a 3-hydroxy group enables reactions such as esterification, phosphorylation, or oxidation to carbonyl-containing motifs, and it can participate in the formation of glycosidic or other linkages in complex biomolecules.

The term is used as a locational descriptor rather than naming a single compound. Many natural products, metabolic intermediates, and biomolecules feature hydroxyl groups at various carbon positions, including position 3. Thus, 3-hydroxyl serves as a useful specification in describing structure, reactivity, and potential biological roles of a molecule.

See also: hydroxyl group; IUPAC nomenclature; carbohydrate stereochemistry; beta-hydroxy and gamma-hydroxy classifications.