Benzopyran

Benzopyran

200px
Identifiers
CAS Number	254-04-6 N
ChemSpider	10651828 Y
InChI InChI=1S/C9H7O/c1-2-6-9-8(4-1)5-3-7-10-9/h1-7H Y Key: QZHPTGXQGDFGEN-UHFFFAOYSA-N Y
Properties
Chemical formula	C9H8O
Molar mass	132.16 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

Benzopyran is an polycyclic organic compound that results from the fusion of a benzene ring to a heterocyclic pyran ring. According to IUPAC nomenclature it is called chromene. There are two isomers of benzopyran that vary by the orientation of the fusion of the two rings compared to the oxygen, resulting in 1-benzopyran (chromene) and 2-benzopyran (isochromene)—the number denotes where the oxygen atom is located by standard naphthalene-like nomenclature.

The radical form of benzopyran is paramagnetic. The unpaired electron is delocalized over the whole benzopyran molecule, rendering it less reactive than one would expect otherwise, a similar example is the cyclopentadienyl radical. Commonly, benzopyran is encountered in the reduced state, in which it is partially saturated with one hydrogen atom, introducing a tetrahedral CH₂ group in the pyran ring. Therefore, there are many structural isomers owing to the multiple possible positions of the oxygen atom and the tetrahedral carbon atom:

Structural isomers of chromene

120px 2H-chromene (2H-1-benzopyran)	120px 4H-chromene (4H-1-benzopyran)
5H-chromene	7H-chromene
8aH-chromene

Structural isomers of isochromene

120px 1H-isochromene (1H-2-benzopyran)

120px 3H-isochromene (3H-2-benzopyran)

See also

• Benzofuran
• Benzopyrone