Pyran 808932 198694839 2008-03-16T20:04:01Z McM.bot 3453363 robot Adding: [[pl:Piran (związek chemiczny)]] {{Chembox new |ImageFileL1=2H-Pyran.png |ImageSizeL1=75px |ImageFileR1=Pyran3d.png |ImageSizeR1=100px |ImageFileL2=4H-Pyran.png |ImageSizeL2=75px |ImageFileR2=4HPyran3d.png |ImageSizeR2=100px |IUPACName=Pyran |OtherNames=2H-Pyran, 4H-Pyran |Section1= {{Chembox Identifiers | CASNo= | PubChem= | SMILES= }} |Section2= {{Chembox Properties | Formula=C<sub>5</sub>H<sub>6</sub>O | MolarMass= | Appearance= | Density= | MeltingPt= | BoilingPt= | Solubility= | pKa = | pKb = }} |Section3= {{Chembox Hazards | MainHazards= | FlashPt= | Autoignition= }} | Section8 = {{Chembox Related | OtherCpds = [[Tetrahydropyran]] }} }} In [[chemistry]], a '''pyran''' is a six membered [[heterocyclic]] ring consisting of five [[carbon]] atoms and one [[oxygen]] atom and containing two [[double bond]]s. The [[molecular formula]] is C<sub>5</sub>H<sub>6</sub>O. There are two [[isomer]]s of pyran that differ by the location of the double bonds. In 2''H''-pyran, the saturated carbon is at position 2, whereas in 4''H''-pyran, the saturated carbon is at position 4. Although the pyrans themselves have little significance in chemistry, a variety of their derivatives are important biological molecules. 4H-pyrane easily disproportionates to the corresponding [[dihydropyrane|dihydropyrane]] and the [[pyrylium]] ion which is easily hydrolyzed in aqueous medium. The term pyran is also often applied to the saturated ring analog which is more properly referred to as [[tetrahydropyran]]. In this context, the [[monosaccharide]]s containing a six-membered ring system are known as [[pyranose]]s. Hence, the six-membered ring form of [[glucose]] is known as D-glucopyranose. == See also == * [[Furan]] [[Category:Oxygen heterocycles]] [[de:Pyrane]] [[fr:Pyrane]] [[it:Pirano (chimica)]] [[nl:Pyraan]] [[ja:ピラン (化学)]] [[pl:Piran (związek chemiczny)]]