Specific rotation, [α]D

Definition

Specific rotation, [α]D, is a standardized measure of a compound's ability to rotate plane-polarized light, reported in degrees. It is calculated at a specified temperature and wavelength, usually 589 nm (the D line of sodium).

Related terms

Optical Activity:

The ability of a substance to rotate the plane of polarization of plane-polarized light.

Chirality:

A property of a molecule that is not superimposable on its mirror image, often leading to optical activity.

Enantiomers:

Pairs of molecules that are non-superimposable mirror images of each other, often with different specific rotations