How many structural işomers of alcohol with molecular formula, `C_(4)H_(9)OH` are possible? Give their IUPAC name. Which one of the isomers is optically active?

Explanation

Structural isomers of `C_(4)H_(9)OH` alcohol.
`underset("Butan-1-ol")(CH_(3)-CH_(2)-CH_(2)-CH_(2)-OH)`
`underset("Butan-2-ol")(CH_(3)-CH_(2)-underset(OH)underset(|)CH-CH_(3)), underset("2-methyl propan-2-ol")(H_(3)C-underset(CH_(3))underset(|)overset(CH_(3))overset(|)C-OH)`
`underset("2-methyl propan-1-ol")(HO-CH_(2)-underset(CH_(3))underset(|)CH-CH_(3))`
Butan-2-ol is an optically active isomer.