Editing Glucose (section)

===Mutarotation===
{{See also|Mutarotation}}
[[File:Mutarotation D-Glucose V.1.png|thumb|upright=2|class=skin-invert-image|Mutarotation: {{sm|d}}-glucose molecules exist as cyclic hemiacetals that are epimeric (= diastereomeric) to each other. The epimeric ratio α:β is 36:64. In the α-D-glucopyranose (left), the blue-labelled hydroxy group is in the axial position at the anomeric centre, whereas in the β-D-glucopyranose (right) the blue-labelled hydroxy group is in equatorial position at the anomeric centre.]]
Mutarotation consists of a temporary reversal of the ring-forming reaction, resulting in the open-chain form, followed by a reforming of the ring. The ring closure step may use a different {{chem2|\sOH}} group than the one recreated by the opening step (thus switching between pyranose and furanose forms), or the new hemiacetal group created on C-1 may have the same or opposite handedness as the original one (thus switching between the α and β forms). Thus, though the open-chain form is barely detectable in solution, it is an essential component of the equilibrium.

The open-chain form is [[Chemical stability|thermodynamically unstable]], and it spontaneously [[isomer]]izes to the cyclic forms. (Although the ring closure reaction could in theory create four- or three-atom rings, these would be highly strained, and are not observed in practice.) In solutions at [[room temperature]], the four cyclic isomers interconvert over a time scale of hours, in a process called [[mutarotation]].<ref>{{McMurry2nd | page = 866}}.</ref> Starting from any proportions, the mixture converges to a stable ratio of α:β 36:64.<!--AT ANY TEMPERATURE?--> The ratio would be α:β 11:89 if it were not for the influence of the [[anomeric effect]].<ref>{{citation | title = The Anomeric Effect | last1 = Juaristi | first1 = Eusebio | first2 = Gabriel | last2 = Cuevas | year = 1995 | publisher = CRC Press | pages = 9–10 | isbn = 978-0-8493-8941-2}}</ref> Mutarotation is considerably slower at temperatures close to {{convert|0|C}}.