enantiotropy

Enantiotropy describes the relationship between two different forms of the same substance that can reversibly transform into each other at a specific transition point. This is a type of polymorphism, where a solid chemical compound can exist in multiple crystalline forms. These forms may have slightly different physical properties, but their solutions and vapors are identical.12

A related concept is enantiomorphism, which refers to mirror-image relationships, like those between a left and right hand. This can apply to crystals or to molecules, known as enantiomers. Molecular enantiomers have identical chemical properties, except when reacting with other chiral molecules or polarized light. This "handedness" is crucial in biological systems, where specific molecular shapes are required for interactions, as seen in the tragic case of thalidomide, where one enantiomer was harmful while the other was less so.345