https://doi.org/10.1351/goldbook.T06434
In medium-sized ring compounds, the @[email protected] due to repulsive @[email protected] between substituents or hydrogen atoms attached to non-adjacent ring atoms.
Source:
PAC, 1996, 68, 2193. (Basic terminology of stereochemistry (IUPAC Recommendations 1996)) on page 2221 [Terms] [Paper]