Pyran
Encyclopedia
In chemistry
, a pyran, or oxine, is a six-membered heterocyclic, non-aromatic ring, consisting of five carbon
atoms and one oxygen
atom and containing two double bond
s. The molecular formula is C5H6O. There are two isomer
s of pyran that differ by the location of the double bonds. In 2H-pyran, the saturated carbon is at position 2, whereas, in 4H-pyran, the saturated carbon is at position 4.
Although the pyrans themselves have little significance in chemistry, many of their derivatives are important biological molecules: 4H-Pyran easily disproportionates to the corresponding dihydropyran 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
(oxane). In this context, the monosaccharide
s containing a six-membered ring system are known as pyranose
s.
Chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....
, a pyran, or oxine, is a six-membered heterocyclic, non-aromatic ring, consisting of five carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
atoms and one oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
atom and containing two double bond
Double bond
A double bond in chemistry is a chemical bond between two chemical elements involving four bonding electrons instead of the usual two. The most common double bond, that between two carbon atoms, can be found in alkenes. Many types of double bonds between two different elements exist, for example in...
s. The molecular formula is C5H6O. There are two isomer
Isomer
In chemistry, isomers are compounds with the same molecular formula but different structural formulas. Isomers do not necessarily share similar properties, unless they also have the same functional groups. There are many different classes of isomers, like stereoisomers, enantiomers, geometrical...
s of pyran that differ by the location of the double bonds. In 2H-pyran, the saturated carbon is at position 2, whereas, in 4H-pyran, the saturated carbon is at position 4.
Although the pyrans themselves have little significance in chemistry, many of their derivatives are important biological molecules: 4H-Pyran easily disproportionates to the corresponding dihydropyran 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
Tetrahydropyran
Tetrahydropyran is the organic compound consisting of a saturated six-membered ring containing five carbon atoms and one oxygen atom. The compound is a colourless volatile liquid, but is obscure. Derivatives of tetrahydropyran are, however, more common. Tetrahydropyranyl ethers derived from the...
(oxane). In this context, the monosaccharide
Monosaccharide
Monosaccharides are the most basic units of biologically important carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose , fructose , galactose, xylose...
s containing a six-membered ring system are known as pyranose
Pyranose
Pyranose is a collective term for carbohydrates that have a chemical structure that includes a six-membered ring consisting of five carbon atoms and one oxygen atom. The name derives from its similarity to the oxygen heterocycle pyran, but the pyranose ring does not have double bonds...
s.