4H-1-Benzopyran
Chemical compound
4H-1-Benzopyran is an organic compound with the formula C6H4C3H4O. It is one of two isomers of benzopyran, the other being 2H-1-benzopyran, which is more prevalent. It can be viewed as the fusion of a benzene ring to a heterocyclic pyran ring.
Some benzopyrans have shown anticancerous activity in vitro.
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:
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) |
01Nomenclature
According to current IUPAC nomenclature, the name chromene used in previous recommendations is retained; however, systematic ‘benzo’ names, for example 2H-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-like nomenclature.
Sources and credits
This article is adapted from the Wikipedia article “4H-1-Benzopyran”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- 4H-Chromen.svg by NEUROtiker (talk), Public domain
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