Chapter 25: Carbohydrates
Mutarotation : interconversion of α- and β- anomers
The
α- and β- anomers
of carbohydrates are typically stable solids.
However, in aqueous solution, they quickly equilibrate to an equilibrium mixture of the two forms.
For example, in aqueous solution, glucose exists as a mixture of 36% α- and 64% β- (>99% of the
pyranose forms
exist in solution).
The equilibration occurs via the ring opening of the cyclic sugar at the anomeric center with the acyclic form as the intermediate.
Or, in a simplified form with all the "extra" hydroxy groups removed:
The curly arrow mechanism involved here is essentially the same as that for acetal formation (
review
?)
©
Dr. Ian Hunt
, Department of Chemistry