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In
chemistry Chemistry is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in the real world. T ...

chemistry
, pyran, or oxine, is a six-membered
heterocyclic 125px, Pyridine, a heterocyclic compound A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different chemical element, elements as members of its ring(s). Heterocyclic chemistry is the branch of organi ...
, non-aromatic ring, consisting of five
carbon Carbon (from la, carbo "coal") is a with the C and 6. It is lic and —making four s available to form s. It belongs to group 14 of the periodic table. Carbon makes up only about 0.025 percent of Earth's crust. Three occur naturally, ...

carbon
atoms and one
oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

oxygen
atom and containing two
double bond In chemistry, a double bond is a between two s involving four s as opposed to two in a . Double bonds occur most commonly between two carbon atoms, for example in s. Many double bonds exist between two different elements: for example, in a group ...

double bond
s. The
molecular formula A chemical formula is a way of presenting information about the chemical proportions of atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes ...
is C5H6O. There are two
isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formulas — that is, same number of atoms of each element (chemistry), element — but distinct arrangements of atoms in space. Isomerism is existence or possibil ...

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. 4''H''-Pyran was first isolated and characterized in 1962 via
pyrolysis The pyrolysis (or devolatilization) process is the of materials at elevated temperatures in an inert atmosphere. It involves a change of . The word is coined from the -derived s ''pyro'' "fire" and ' "separating". Pyrolysis is most commonly us ...

pyrolysis
of 2-acetoxy-3,4-dihydro-2''H''-pyran. It was found too unstable, particularly in the presence of air. 4''H''-pyran easily disproportionates to the corresponding
dihydropyranIn organic chemistry, dihydropyran refers to two heterocyclic compounds with the chemical formula, formula C5H8O: *3,4-Dihydropyran, 3,4-Dihydro-2''H''-pyran *3,6-dihydro-2''H''-pyran Nomenclature In IUPAC names, "dihydro" refers to the two added ...
and the
pyrylium Pyrylium is a cation An ion () is a particle, atom or molecule with a net electric charge, electrical charge. The charge of the electron is considered negative by convention. The negative charge of an ion is equal and opposite to charged p ...

pyrylium
ion, which is easily hydrolyzed in aqueous medium. Although the pyrans themselves have little significance in chemistry, many of their derivatives are important biological molecules, such as the pyranoflavonoids. The term pyran is also often applied to the saturated ring analog, which is more properly referred to as
tetrahydropyran Tetrahydropyran (THP) is the organic compound consisting of a saturated six-membered ring containing five carbon atoms and one oxygen atom. It is named by reference to pyran, which contains two double bonds, and may be produced from it by adding ...

tetrahydropyran
(oxane). In this context, the
monosaccharide Monosaccharides (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is ap ...
s containing a six-membered ring system are known as
pyranosePyranose is a collective term for saccharides that have a chemical structure that includes a six-membered ring consisting of five carbon atoms and one oxygen atom. There may be other carbons external to the ring. The name derives from its similarity ...
s.


See also

*
Furan Furan is a heterocyclic 125px, Pyridine, a heterocyclic compound A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different chemical element, elements as members of its ring(s). Heterocyclic chemis ...

Furan
*
Furfural Furfural is an organic compound with the formula C4H3OCHO. It is a colorless liquid, although commercial samples are often brown. It has an aldehyde group attached to the 2-position of furan. It is a product of the dehydration reaction, dehydrat ...

Furfural
*
Pyrone
Pyrone
*
Thiopyran Thiopyran is a heterocyclic compound 125px, Pyridine, a heterocyclic compound A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different chemical element, elements as members of its ring(s). Heteroc ...


References

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