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In
chemistry, a
nitrogen compound like
ammonia in a
trigonal pyramid geometry undergoes rapid
nitrogen inversion whereby the
molecule turns inside out. This interconversion is a room
temperature process because the energy barrier (24.2 kJ/mol) is relatively small. Contrast this to
phosphine which does not show inversion at room temperature (energy barrier: 132 kJ/mol) <ref>Kölmel, C.; Ochsenfeld, C.; Ahlrichs, R. An ab initio investigation of structure and inversion barrier of triisopropylamine and related amines and phosphines.
Theor. Chim. Acta. 1991,
82, 271-284.
doi:10.1007/BF01113258</ref>. Even if all three substituents on the nitrogen in an
amine are different, rapid inversion would prevent the nitrogen
atom from becoming a permanent
chiral center, since such inversion becomes effectively like a conformational change.
However, if the nitrogen is a bridgehead atom in a bicyclo or a similar compound where it cannot invert around the lone electron pair, then the nitrogen atom could be a chiral center if all three substituents on it are effectively different. An example of such a compound is Tröger's base.
In one study the inversion in an aziridine was slowed down by a factor of 50 by placing the nitrogen atom in the vicinity of an phenolic alcohol group compared to the oxidized hydroquinone <ref>Control of Pyramidal Inversion Rates by Redox Switching Mark W. Davies, Michael Shipman, James H. R. Tucker, and Tiffany R. Walsh J. Am. Chem. Soc.; 2006; 128(44) pp 14260 - 14261; (Communication) DOI:10.1021/ja065325f</ref> :
- Image:Nitrogeninversionexample.png
The system interconverts by oxidation by oxygen and reduction by sodium dithionate.
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