Furan

• Furfurane
• Divinylenoxid
• Oxacyclopentadien
• Oxol

Colorless liquid Odor chloroformartigem

Liquid

0.94 g · cm -3

-86 ° C

32 ° C.

658 hPa ( 20 ° C)

Poorly in water (10 g · l-1 at 20 ° C)

1.421 (20 ° C)

Risk

-62.3 KJ / mol

Template: Infobox chemical / molecular formula search available

Furan ( furfurane ) is a poorly water -soluble organic liquid from the group of oxygen heterocycles or enol ethers.

History

The name of furan is derived from the Latin word furfur from sharps. First furan presented the chemist Carl Wilhelm Scheele in 1780 furan -2 -carboxylic acid ( furoic acid) ago. Johann Wolfgang Dobereiner reported in 1831 by another important derivative, the furfural, nine years later it was the Scottish chemist John Stenhouse characterize. Furan introduced in 1870, the chemist Heinrich Limpricht ago. He called it incorrectly tetraphenol.

The World Health Organization (WHO ) has classified furan as possibly carcinogenic to humans. The exact effect in the human body, however, has yet to be clarified.

Production and representation

Furan is produced industrially from furfural ( furan -2-carbaldehyde ). This can be obtained by distillation of bran with sulfuric acid. Decarbonylation ( elimination of carbon monoxide ) of furfural, it is heated together with zinc oxide and chromium ( III) oxide at 400 ° C. In an alternative synthesis route, the furfural is first oxidized with oxygen to the furan-2 -carboxylic acid and then converted by decarboxylation to furan. A further possibility for the synthesis of furan and derivatives thereof provides the conversion of 1,4 -dicarbonyl compounds ( for furan butanedial required) with dry HCl gas or phosphorus ( V) oxide

Properties

Furan is an aromatic: A five-membered ring with oxygen hetero- atom, in which six π - electrons are delocalized over the ring. Here come four electrons from the two double bonds and two electrons from the p- orbital of the sp2 hybridized oxygen atom. Thus, it is one of the heteroaromatics and the heterocycles. The aromatic character is weaker than that of pyrrole and thiophene pronounced.

Furan has a low boiling point (32 ° C) and even at room temperature has a high vapor pressure. It is flammable and - due to the high vapor pressure - extremely flammable.

Use

An important reaction is the hydrogenation of furan to the cyclic ether is tetrahydrofuran, which is often used as the solvent.

Furan resins are in the casting, mixed with sand, used as a molding material into the mold boxes.

Furan is included among others in the coffee where it is used as a flavor carrier, what. ZDFzoom in a documentary series that relies on scientific investigations, as a potential health risk was classified The furan content is directly dependent on the applied Brühmethode.

Derivatives

Furan derivatives occur in flavors and fragrances and serve in nature as pheromones. Furanoid fatty acids are synthesized by various plants and fatty acids can be detected in a variety of organisms.

Similar structures form some carbohydrates (sugars), these are called furanose, but contain no double bonds in the ring.