Atoms or groups of a molecule which are related by an n-fold rotation axis (n = 2, 3, etc.) are called homotopic. For example, @[email protected] tartaric acid (\(C_{2}\) axis), chloroform (\(C_{3}\) axis) and cyclohexaamylose (α-cyclodextrin, \(C_{6}\) axis) have respectively two homotopic carboxyl groups, three homotopic chlorine atoms and six homotopic d-glucose residues.
PAC, 1996, 68, 2193. (Basic terminology of stereochemistry (IUPAC Recommendations 1996)) on page 2210 [Terms] [Paper]