Optical activity of lactic acid : In lactic acid molecule there is an asymmetric chiral carbon atom with four different groups which lead to spatial configurations (d-lactic acid and l-lactic acid) which are super imposable mirror images of each other.
`H-underset("* Chiral Carbon atom")underset(" "CH_(3))underset(|)overset(" "COOH)overset(|**)(C)-OH`
The structures of two enantiomers of lactic acid are as follows :
When a plane polarized light is passed through a lactic acid solution, the plane of polarized light gets ratated through a certain angle. This property of rotating the plane of polarized light towards right rotating the plane of polarized light towards right (clockwase) or towards (left) (anticlockwise) is called optical activity.
d-lactic acid rotates the plane of polarized light towards right whereas l-lactic acid rotates the plane of polarized light towards left, which can be detected by polarimeter. In above structures, structure (I) is representing the (+) isomeric from or dextro rotatory from of lactic acid, while structure (II) is representing (-) isomeric from or leavo rotatory from of lactic acid.
