Optical isomer

Optical Isomerism

Optical isomerism is a form of stereoisomerism, a phenomenon in chemistry that describes the spatial arrangement of atoms or groups within molecules. This type of isomerism is specifically related to the properties of chirality (handedness) and the ability of certain compounds to rotate the plane of polarized light.

Overview

Optical isomers, also known as enantiomers, are non-superimposable mirror images of each other, much like left and right hands. This characteristic is due to the presence of a chiral center, typically a carbon atom bonded to four different groups. The term "optical" is derived from the historical use of polarized light to distinguish between these isomers.

Chirality

Chirality in chemistry refers to a molecular asymmetry where the molecule and its mirror image are not superimposable. Chiral molecules lack an internal plane of symmetry and have a stereocenter, most commonly a carbon atom with four different substituents. The two mirror images of a chiral molecule are called enantiomers or optical isomers.

Optical Activity

Optical isomers can exhibit optical activity, the ability to rotate the plane of polarized light. When a beam of plane-polarized light passes through a solution of an optical isomer, the plane of polarization is rotated. The direction and degree of rotation depends on the nature of the isomer. One enantiomer will rotate the plane of polarization in a clockwise direction (dextrorotatory), while the other will rotate it in a counterclockwise direction (levorotatory).

Applications

Optical isomerism has significant implications in many fields, particularly in pharmaceuticals and biochemistry. Many biological molecules are chiral, including amino acids and sugars, and often only one optical isomer is biologically active. In pharmaceuticals, the different enantiomers of a drug can have different levels of efficacy and side effects.

See Also

• Stereochemistry
• Chirality (chemistry)
• Polarized light
• Pharmaceuticals
• Biochemistry