`(pm)`-2 Butanol is a racemic mixture and hence contains equal amounts of the two enantiomers, i.e, (+)-2- butanol and (-)-2- butanol. Whereas (+)-2-butanol rotates the plane of polarized light toward right, (-)-2-butanol rotates the plane of polarized light towards left but to the same extent. The overall rotation is zero and hence `(pm)`-2-butanol is optically inactive.
