The relationship between a molecule's stereoisomers and its optical activity lies in the fact that certain stereoisomers, specifically enantiomers, can rotate plane-polarized light in different directions. Optical activity is the ability of a chiral molecule to rotate the plane of polarization of plane-polarized light. Chiral molecules are those that have a non-superimposable mirror image, meaning they have a central carbon atom with four different groups attached to it.Enantiomers are a type of stereoisomer that are mirror images of each other but are not superimposable. They have the same chemical and physical properties, except for their interaction with plane-polarized light and their reactions with other chiral molecules. One enantiomer will rotate plane-polarized light in a clockwise direction dextrorotatory or + -enantiomer , while the other enantiomer will rotate it in a counterclockwise direction levorotatory or - -enantiomer .A common example of a chiral molecule is 2-butanol CH3CH OH CH2CH3 . It has a chiral center at the second carbon atom, which is bonded to four different groups: a hydrogen atom, a hydroxyl group, a methyl group, and an ethyl group. The two enantiomers of 2-butanol are:1. R -2-butanol: The dextrorotatory + enantiomer, which rotates plane-polarized light in a clockwise direction.2. S -2-butanol: The levorotatory - enantiomer, which rotates plane-polarized light in a counterclockwise direction.These two enantiomers have the same chemical and physical properties, but their optical activities differ due to their distinct spatial arrangements. When a mixture contains equal amounts of both enantiomers, it is called a racemic mixture, and it exhibits no net optical activity because the rotations caused by the two enantiomers cancel each other out.