Definition of Homotopic

1. Atoms or groups of a molecule which are related by an n-fold rotation axis (n = 2, 3, etc) are called homotopic. For example, chiral tartaric acid (C2 axis), chloroform (C3 axis) and cyclohexaamylose (-cyclodextrin, C6 axis) have respectively two homotopic carboxyl groups, three homotopic chlorine atoms and six homotopic D-glucose residues. See prochirality.