Benzopyran is a polycyclic organic compound that results from the fusion of a benzene ring to a heterocyclic pyran ring. According to current IUPAC nomenclature, the name chromene used in previous recommendations is retained; however, systematic ‘benzo’ names, for example 2''H''-1-benzopyran, are preferred IUPAC names for chromene, isochromene, chromane, isochromane, and their chalcogen analogues. 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 Naphthalene is an organic compound with formula . It is the simplest polycyclic aromatic hydrocarbon, and is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromati ...

-like nomenclature. Some benzopyrans have shown anticancerous activity '' in vitro''. The

radical Radical may refer to: Politics and ideology Politics *Radical politics, the political intent of fundamental societal change *Radicalism (historical), the Radical Movement that began in late 18th century Britain and spread to continental Europe and ...

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 Cyclopentadienyl can refer to *Cyclopentadienyl anion, or cyclopentadienide, **Cyclopentadienyl ligand *Cyclopentadienyl radical, • *Cyclopentadienyl cation, See also *Pentadienyl In organic chemistry, pentadienyl refers to the organic radic ...

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:

References

{{Authority control Benzopyrans