Furan
Chemical name	Furan
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
Missing image Furan_chemical_structure.png Chemical structure of tetrahydrofuran

Furan, also known as furane and furfuran, is an aromatic heterocyclic organic compound. 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.

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. Due to its aromaticity, furan behaves not as a typical heterocyclic ether like tetrahydrofuran.

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.
• Benzofuran, furan with a fused benzene ring.
• Dibenzofuran, a compound class similar to dibenzodioxins.
• Simple aromatic rings

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