Pyran

2H-pyran

4H-pyran

Names

IUPAC name

2H-Pyran, 4H-Pyran

Other names

2H-Oxine, 4H-Oxine

Identifiers

CAS Number

289-66-7 (2H)^Y
289-65-6 (4H)^Y

3D model (JSmol)

(2H): Interactive image
(4H): Interactive image

ChemSpider

161812 (2H)^Y
119912 (4H)^Y

PubChem CID

186148 (2H)
136135 (4H)

UNII

CH5P2A5WTT^Y

CompTox Dashboard (EPA)

DTXSID80893659

InChI

(2H): InChI=1S/C5H6O/c1-2-4-6-5-3-1/h1-4H,5H2
Key: MGADZUXDNSDTHW-UHFFFAOYSA-N
(4H): InChI=1S/C5H6O/c1-2-4-6-5-3-1/h2-5H,1H2
Key: MRUWJENAYHTDQG-UHFFFAOYSA-N

SMILES

(2H): C1=CC=CCO1
(4H): C1=CCC=CO1

Properties

Chemical formula

C₅H₆O

Molar mass

82.102 g·mol⁻¹

Related compounds

Dihydropyran
Tetrahydropyran

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Infobox references

Chemical compound

In chemistry, pyran, or oxine, is a six-membered heterocyclic, non-aromatic ring, consisting of five carbon atoms and one oxygen atom and containing two double bonds. The molecular formula is C₅H₆O. There are two isomers of pyran that differ by the location of the double bonds. In 2H-pyran, the saturated carbon is at position 2, whereas, in 4H-pyran, the saturated carbon is at position 4.

4H-Pyran was first isolated and characterized in 1962 via pyrolysis of 2-acetoxy-3,4-dihydro-2H-pyran.^[1] It was found to be unstable, particularly in the presence of air. 4H-pyran easily disproportionates to the corresponding dihydropyran and the pyrylium ion, which is easily hydrolyzed in aqueous medium.

Although the pyrans themselves have little significance in chemistry, many of their derivatives are important biological molecules, such as the pyranoflavonoids.

The term pyran is also often applied to the saturated ring analog, which is more properly referred to as tetrahydropyran (oxane). In this context, the monosaccharides containing a six-membered ring system are known as pyranoses.