Pyridinium

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Pyridinium
IUPAC name pyridinium
Identifiers
CAS number	16969-45-2 Y
PubChem	4989215
ChemSpider	4169387 Y
Jmol-3D images	Image 1
SMILES [nH+]1ccccc1
InChI InChI=1S/C5H5N/c1-2-4-6-5-3-1/h1-5H/p+1 Y Key: JUJWROOIHBZHMG-UHFFFAOYSA-O Y InChI=1S/C5H5N/c1-2-4-6-5-3-1/h1-5H/p+1 InChI=1S/C5H5N/c1-2-4-6-5-3-1/h1-5H/p+1 Key: JUJWROOIHBZHMG-UHFFFAOYSA-O
Properties
Molecular formula	C5H6N
Molar mass	80.11 g mol−1
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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 electrons 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 reactions, 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

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