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4H-1-Benzopyran is an
organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...
with the formula . It is one of two isomers of benzopyran, the other being
2H-1-benzopyran 2H-1-Benzopyran is an organic compound with the formula . It is one of two isomers of benzopyran, the other being 4H-1-Benzopyran, 4H-1-benzopyran, which is less prevalent. It can be viewed as the fusion of a benzene ring to a heterocyclic pyran r ...
, 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:


Nomenclature

According to current
IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...
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-like nomenclature.


See also

* Benzofuran * Benzopyrone


References

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