Term: anti
https://doi.org/10.1351/goldbook.A00381

Definition:
Two substituents attached to atoms joined by a single bond are anti if the torsion angle (dihedral angle) between the bonds to the substituents is greater than 90°, or syn if it is less than 90°. (A further distinction is made between antiperiplanar, synperiplanar, anticlinal and synclinal.)

Related Terms:
1) torsion angle (http://doi.org/10.1351/goldbook.T06406).
2) dihedral angle (http://doi.org/10.1351/goldbook.D01730).
3) syn (http://doi.org/10.1351/goldbook.S06216).
4) antiperiplanar (http://doi.org/10.1351/goldbook.T06406-1).
5) synperiplanar (http://doi.org/10.1351/goldbook.T06406-2).
6) anticlinal (http://doi.org/10.1351/goldbook.T06406-3).
7) synclinal (http://doi.org/10.1351/goldbook.T06406-4).

Source: 

Citation: 'anti' 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.A00381

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