Benzopyran is an polycyclic

Polycyclic compound

In organic chemistry, a polycyclic compound is a cyclic compound with more than one hydrocarbon loop or ring structures . In general, the term includes all polycyclic aromatic compounds, including the polycyclic aromatic hydrocarbons, the heterocyclic aromatic compounds containing sulfur,...

 organic compound

Organic compound

An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 that results from the fusion of a benzene

Benzene

Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....

 ring to a heterocyclic pyran

Pyran

In chemistry, a 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...

 ring. According to IUPAC nomenclature it is called chromene. There are two isomers of benzopyran depending on the orientation of the fusion of the two rings, resulting in 1-benzopyran (chromene) and 2-benzopyran (isochromene). Due to a single unpaired electron, benzopyran has is found to be paramagnetic. The unpaired electron is delocalized over the whole benzopyran molecule, rendering it less reactive than one would expect otherwise, a similar example is cyclopentadienyl. Commonly, benzopyran is encountered in the reduced state, where it is partially saturated with one hydrogen. This reduced state has four structural isomers depending on where the hydrogen is attacking:

2H-Chromene

4H-Chromene

5H-Chromene

7H-Chromene

8aH-Chromene