Term: homotopic https://doi.org/10.1351/goldbook.H02857 Definition: 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 (α-cyclodextrin, C6 axis) have respectively two homotopic carboxyl groups, three homotopic chlorine atoms and six homotopic d-glucose residues. Related Terms: 1) chiral (http://doi.org/10.1351/goldbook.C01057). 2) prochirality (http://doi.org/10.1351/goldbook.P04859). Source: PAC, 1996, 68, 2193. 'Basic terminology of stereochemistry (IUPAC Recommendations 1996)' on page 2210 (https://doi.org/10.1351/pac199668122193) Citation: 'homotopic' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.H02857 License: The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.