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| Identifiers | |
|---|---|
3D model (JSmol) | |
| 111589 | |
| ChEBI | |
| ChemSpider |
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| |
| |
| Properties | |
| C9H8O | |
| Molar mass | 132.162 g·mol−1 |
| Appearance | colorless |
| Density | 1.0732 g/cm3 |
| Boiling point | 80 °C (176 °F; 353 K) 13 Torr |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
4H-1-Benzopyran is anorganic compound with the formulaC6H4C3H4O. It is one of two isomers of benzopyran, the other being2H-1-benzopyran, which is more prevalent. It can be viewed as the fusion of abenzene ring to aheterocyclicpyran ring.[1]
Some benzopyrans have shown anticancerous activityin vitro.[2]
Theradical form of benzopyran isparamagnetic. The unpaired electron is delocalized over the whole benzopyran molecule, rendering it less reactive than one would expect otherwise. A similar example is thecyclopentadienyl 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:
 2H-chromene (2H-1-benzopyran) | 4H-chromene (4H-1-benzopyran) |
| 5H-chromene | 7H-chromene |
| 8aH-chromene |
 1H-isochromene (1H-2-benzopyran) |  3H-isochromene (3H-2-benzopyran) |
According to currentIUPAC nomenclature, the namechromene used in previous recommendations is retained; however, systematic ‘benzo’ names, for example 2H-1-benzopyran, arepreferred IUPAC names for chromene, isochromene, chromane, isochromane, and their chalcogen analogues.[3] 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 standardnaphthalene-like nomenclature.
