Eclipsed conformation
In chemistry an eclipsed conformation is a conformation in which two substituents X and Y on adjacent atoms A, B are in closest proximity, implying that the torsion angle X–A–B–Y is 0°.[1] Such a conformation exists in any open chain, single chemical bond connecting two sp3-hybridised atoms, and it is normally a conformational energy maximum. This maximum is often explained by steric hindrance, but its origins sometimes actually lie in hyperconjugation (as when the eclipsing interaction is of two hydrogen atoms).
![](../I/Eclipsed_Conformation.svg.png.webp)
(image right in Newman projection)
In the example of ethane in Newman projection it shows that rotation around the carbon-carbon bond is not entirely free but that an energy barrier exists. The ethane molecule in the eclipsed conformation is said to suffer from torsional strain and by a rotation around the carbon carbon bond to the staggered conformation around 12.5 kJ/mol of torsional energy is released.
See also
References
- Eliel, Ernest L.; Wilen, Samuel H. (1994). Stereochemistry of Organic Compounds. Wiley. p. 1197. ISBN 978-0-471-01670-0.