Butan-2-ol, or sec-butanol, is an organic compound with formula CH3CH(OH)CH2CH3. Its structural isomers are 1-butanol, isobutanol, and tert-butanol. 2-Butanol is chiral and thus can be obtained as either of two stereoisomers designated as (R)-(−)-butan-2-ol and (S)-(+)-butan-2-ol. It is normally encountered as a 1:1 mixture of the two stereoisomers — a racemic mixture.
This secondary alcohol is a flammable, colorless liquid that is soluble in three parts water and completely miscible with organic solvents. It is produced on a large scale, primarily as a precursor to the industrial solvent methyl ethyl ketone.