Furan

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Furan
Chemical name	Furan
Other names	oxole, furfuran, divinyl oxide
Chemical formula	C₄H₄O
Molecular mass	68.07 g/mol
Melting point	−85.6 °C
Boiling point	31.4 °C
Density	0.936 g/cm³
CAS number	110-00-9
SMILES	C1=CC=CO1

Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Furan, also known as furane and furfuran, is a heterocyclic organic compound, produced when wood, especially pine-wood, is distilled. Furan is a clear, colorless, very volatile and highly flammable liquid with a boiling point close to room temperature. It is toxic and may be carcinogenic. Catalytic hydrogenation (see redox) of furan with a palladium catalyst gives tetrahydrofuran.

Furan is aromatic because one of the lone pairs of electrons on the oxygen atom is delocalized into the ring, creating a 4n+2 aromatic system (see Hückel's rule) similar to benzene. This aromatic system forms two rings of electrons above and below the flat structure with no discrete double bonds. The other lone pair of electrons of the oxygen atom extends in the plane of the flat ring system.

1 Synthesis
2 Reactions
3 See also
4 External links
5 References

[edit] Synthesis

A classic furan organic synthesis is the Feist-Benary synthesis.
One of the most simple synthesis methods for furans is the reaction of 1,4-diketones with diphosphorus pentoxide (P_{2_{O_{5_{) in the Paal-Knorr Synthesis. It is interesting that the thiophene formation reaction of 1,4-diketones with lawesson's reagent also forms furans as side products.}}}}

[edit] Reactions

Due to its aromaticity, furan's behavior is quite dissimilar to that of the more typical heterocyclic ethers such as tetrahydrofuran. It is considerably more reactive than benzene in electrophilic substitution reactions.
Furan is a diene in Diels-Alder reactions with electron-deficient dienophiles such as ethyl (E)-3-nitroacrylate.<ref>The oxanorbornene approach to 3-hydroxy, 3,4-dihydroxy and 3,4,5-trihydroxy derivatives of 2-aminocyclohexanecarboxylic acid Masesane I, Batsanov A, Howard J, Modal R, Steel P Beilstein Journal of Organic Chemistry, 2006 2:9 Online Article</ref> The reaction product is a mixture of isomers with preference for the endo isomer: