Pyridine N-oxide

Pyridine-N-oxide

Names
IUPAC name Pyridine-N-oxide
Other names pyridine-1-oxide
Identifiers
CAS Number	694-59-7 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:29136 Y
ChemSpider	12229 Y
ECHA InfoCard	100.010.705
PubChem	12753
InChI InChI=1S/C5H5NO/c7-6-4-2-1-3-5-6/h1-5H Y Key: ILVXOBCQQYKLDS-UHFFFAOYSA-N Y InChI=1/C5H5NO/c7-6-4-2-1-3-5-6/h1-5H Key: ILVXOBCQQYKLDS-UHFFFAOYAZ
SMILES c1cc[n+](cc1)[O-]
Properties
Chemical formula	C5H5NO
Molar mass	95.101
Appearance	colourless solid
Melting point	65 to 66 °C (149 to 151 °F; 338 to 339 K)
Boiling point	270 °C (518 °F; 543 K)
Solubility in water	high
Acidity (pKa)	0.8 (of conjugate acid)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

Pyridine-N-oxide is the heterocyclic compound with the formula C₅H₅NO. This colourless, hygroscopic solid is the product of the oxidation of pyridine. It was originally prepared using peracids as the oxidising agent. The molecule is planar. The compound is used infrequently as an oxidizing reagent in organic synthesis. It also serves as a ligand in coordination chemistry, and to activate the pyridine ring towards aromatic electrophilic substitution.

The oxidation of pyridine can be achieved with a number of peracids including peracetic acid and perbenzoic acid in a reaction that affords the protonated derivative. Subsequent treatment with heating under low pressure removes acids as gases to liberates the neutral oxide. More recent reported approaches include a modified Dakin reaction using a urea-hydrogen peroxide complex, and oxidation by sodium perborate or, using methylrhenium trioxide (CH
3ReO
3) as catalyst, with sodium percarbonate. Pyridine N-oxide is five orders of magnitude less basic than pyridine, but it is isolable as a hydrochloride salt, [C₅H₅NOH]Cl, via a synthesis reported in Organic Syntheses: