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| colspan=3 |'''Inversion of an amine.''' <small>The C<sub>3</sub> axis of the amine is presented as horizontal, and the pair of dots represent the lone pair of the nitrogen atom collinear with that axis. A mirror plane can be imagined to relate the two amine molecules on either side of the arrows. If the three R groups attached to the nitrogen are all unique, then the amine is chiral; whether it can be isolated depends on the [[Gibbs energy|free energy]] required for the molecule's inversion.</small>
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Pyramidal inversion in [[nitrogen]] and [[amine]]s is known as '''nitrogen inversion'''.<ref>{{Cite journal|last1=Ghosh|first1=Dulal C.|last2=Jana|first2=Jibanananda|last3=Biswas|first3=Raka|date=2000|title=Quantum chemical study of the umbrella inversion of the ammonia molecule|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/1097-461X%282000%2980%3A1%3C1%3A%3AAID-QUA1%3E3.0.CO%3B2-D|journal=International Journal of Quantum Chemistry|language=en|volume=80|issue=1|pages=1–26|doi=10.1002/1097-461X(2000)80:1<1::AID-QUA1>3.0.CO;2-D|issn=1097-461X|url-access=subscription}}</ref> It is a [[Molecular vibration|rapid oscillation]] of the nitrogen atom and substituents, the nitrogen "moving" through the plane formed by the substituents (although the substituents also move - in the other direction);<ref>{{Greenwood&Earnshaw2nd|page=423}}</ref> the molecule passing through a [[Trigonal planar molecular geometry|planar]] [[transition state]].<ref>{{ cite journal | author = J. M. Lehn | author-link = Jean-Marie Lehn | title = Nitrogen Inversion: Experiment and Theory | journal = [[Fortschritte der Chemischen Forschung|Fortschr. Chem. Forsch.]] | year = 1970 | volume = 15 | pages = 311–377 | doi = 10.1007/BFb0050820 }}</ref> For a compound that would otherwise be [[Chirality (chemistry)|chiral]] due to a nitrogen [[stereocenter]], nitrogen inversion provides a low energy pathway for [[racemization]], usually making [[chiral resolution]] impossible.<ref>{{March6th|pages=142–145}}</ref>
===Quantum effects===
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