Answer
Axial chirality, a unique form of chirality, was predicted by van't Hoff for cumulenes, compounds with consecutive double bonds. This chirality arises from the restricted rotation around the double bonds, leading to non-superimposable mirror images. The axial chirality of cumulenes is distinct from the planar chirality observed in alkenes and the helical chirality of helicenes, demonstrating the diverse range of chirality in organic molecules.