A term used to describe the fact that a and b anomers of carbohydrates can equilibrate via the open-chain form.
The charge in the optical rotation because of the change in equilibrium between two anomers. The a- and B- anomers of carbohydrates are typically stable solids. However, in aqueous solution, they quickly equilibrate to an equilibrium mixture of the two forms. The equilibrium occurs in the ring opening of the cyclic sugar at the anomeric center with the acyclic form as the intermediate.