Chirality is generally understood as the property of an object to differ from its mirror image. An example for chirality are our hands. The right and left hand behave to each other like a mirror image.

In chemistry, chirality refers to a spatial arrangement of atoms in a molecule in which certain symmetry operations, their mirror image by rotation, cannot be made to coincide with the original. Objects with this property are called chiral.

If two molecules differ from each other only in that the substituents on the asymmetric carbon atom are arranged differently, then they behave to each other like image and mirror image, forming two structural isomers or enantiomers. For a molecule to be chiral, certain conditions must be met.

Accordingly, the different molecules can have different effects. Examples are: LSD-25 and ISO-LSD or the S- and R-ketamine.