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 |
| Flash Point | -35 C |
| CAS number | 110-00-9 |
| SMILES | C1=CC=CO1 |
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| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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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. Note that this implies that oxygen is sp2 hybridized whereas one would normally believe it to be sp3. The sp2 hybridization is to allow one of the lone pairs of oxygen to reside in a p orbital and thus allow it to interact within the pi system. This allows the extra aromatic stabilization.
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[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 phosphorus pentoxide (P2O5) 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.[1] The reaction product is a mixture of isomers with preference for the endo isomer:
- Furans are hydrogenated to dihydrofurans and tetrahydrofurans.
[edit] See also
- Tetrahydrofuran (THF), the fully hydrogenated analog of furan and a common solvent.
- Pyrrole, the nitrogen analog of furan.
- Thiophene, the sulfur analog of furan.
- Selenophene, the selenium analog of furan.
- Tellurophene, the tellurium analog of furan.
- Benzofuran, furan with a fused benzene ring.
- Dibenzofuran, a compound class similar to dibenzodioxins.
- Simple aromatic rings
[edit] External links
[edit] References
- ^ 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
