Furan
In chemistry, furan, C4H4O is a pentacyclic ring compound with four carbon atoms and one oxygen atom forming the ring.
It is often drawn with each carbon atom within the ring having a single bond to another atom in the ring, one externally to hydrogen, and a double bond to another carbon.
The lone pair of the oxygen atom is delocalised into the ring, creating a 4n+2 aromatic system, in a similar way to which a carbon-carbon double bond is in benzene, thereby creating a ring of electrons around the structure with no discrete double or single bonds.
Often used as a solvent the most commonly used derivative of a furan is tetra-hydrofuran, C4H8O (often abbreviated to THF).
