{"term":{"id":"12187","title":"rotational isomeric state","longtitle":"IUPAC Gold Book - rotational isomeric state","doi":"10.1351\/goldbook.12187","code":"12187","status":"current","synonym":"<em>synonym<\/em>: bond-conformational state (in polymer science)","definitions":[{"id":1,"text":"Rotamer defined by a relative rotation about a skeletal bond of a single-strand chain.","notes":{"1":"A rotational isomeric state is conventionally defined over a sequence of three contiguous skeletal bonds with reference to the dihedral (or torsion) angle (\\(\\phi\\)) between the planes defined by the first two bonds and the second two bonds. For example, for a chain composed of single \\(\\ce{C-C}\\) skeletal bonds, \\(\\phi \\approx 0^{\\circ}\\) can be used to define the (planar) trans (\\(t\\)) rotational isomeric state, and \\(\\phi \\approx \\pm 120^{\\circ}\\) to define the gauche\\(\\pm\\) (\\(g_{\\pm}\\)) rotational isomeric states.","2":"Alternative notations exist. For example, \\(\\phi = 180°, \\pm 60^{\\circ}\\), respectively, can be used to denote the \\(t\\) and \\(g_{\\pm}\\) states, which can also be given the symbols \\(\\rm{T}\\), \\(\\rm{G}^{+}\\), and \\(\\rm{G}^{-}\\). The trans and gauche states or conformers are also known as the \"antiperiplanar conformers\" and \"synclinal conformers\". The notation used in Note 1 is that introduced by Flory and co-workers and is now the one most frequently used in polymer science.","3":"The energies of rotational isomeric states are determined by short-range intramolecular interactions."},"contexts":[],"sources":["PAC, 2015, 87, 71. 'Definitions of terms relating to individual macromolecules, macromolecular assemblies, polymer solutions, and amorphous bulk polymers (IUPAC Recommendations 2014)' on page 74 (https:\/\/doi.org\/10.1515\/pac-2013-0201)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/12187\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/12187\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/12187\/plain"},"citation":"Citation: 'rotational isomeric state' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351\/goldbook.12187","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.","collection":"If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .","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.","accessed":"2026-08-10T08:08:19+00:00"}}