What defines a chiral carbon?

A chiral carbon is defined specifically as a carbon atom that is bonded to four different substituents. This unique arrangement leads to non-superimposable mirror images of the molecule, known as enantiomers. The presence of four distinct substituents means that if you were to create a mirror image of the molecule, it would not be identical to the original, which is a key characteristic of chirality.

This property is foundational in biochemistry, as the interactions of chiral molecules, such as amino acids and sugars, often dictate their biological functions and behaviors. In contrast, carbon atoms with identical substituents or fewer than four substituents cannot exhibit this kind of isomerism and therefore do not qualify as chiral.