Pyridinium
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188197242
2008-01-31T18:26:24Z
72.5.24.11
[[Image:Pyridinium.svg|frame|right|Pyridinium cation]]
'''Pyridinium''' refers to the [[cationic]] form of [[pyridine]]. This can either be due to [[protonation]] of the ring nitrogen or because of addition of a substituent to the ring nitrogen, typically via [[alkylation]]. The [[lone pair]] of [[electron]]s on the [[nitrogen]] [[atom]] of pyridine is not [[delocalized]], and thus pyridine can be protonated easily. Pyridine is often used as an organic base in chemical reations, thus the pyridinium [[ion]] is produced as the counter ion to the leaving group in the reaction. This complex is often [[insoluble]] in the organic solvent, so precipitation of the pyridinium leaving group complex is an indication of the progress of the reaction.
The pyridinium ion also plays a role in [[Friedel-Crafts acylation]]. When pyridine is included, it forms a complex with the electrophillic [[acylium]] ion, rendering it even more reactive.
==See also==
* [[Pyridinium chlorochromate]]
[[Category:nitrogen heterocycles]]
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