Furan

Furan is a heterocyclic organic compound, consisting of a five-membered aromatic ring with four carbon atoms and one oxygen. Chemical compounds containing such rings are also referred to as furans.The name 'furan' comes from the Latin furfur, which means bran. The first furan derivative to be described was 2-furoic acid, by Carl Wilhelm Scheele in 1780. Another important derivative, furfural, was reported by Johann Wolfgang Döbereiner in 1831 and characterised nine years later by John Stenhouse. Furan itself was first prepared by Heinrich Limpricht in 1870, although he called it 'tetraphenol' (as if it were a four-carbon analog to phenol, C6H6O).Industrially, furan is manufactured by the palladium-catalyzed decarbonylation of furfural, or by the copper-catalyzed oxidation of 1,3-butadiene: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. Because of the aromaticity, the molecule is flat and lacks discrete double bonds. The other lone pair of electrons of the oxygen atom extends in the plane of the flat ring system. 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 π system.Furan is found in heat-treated commercial foods and is produced through thermal degradation of natural food constituents. It can be found in roasted coffee, instant coffee, and processed baby foods. Research has indicated that coffee made in espresso makers, and, above all, coffee made from capsules, contains more furan than that made in traditional drip coffee makers, although the levels are still within safe health limits.