What does the term anomeric effect refer to?
In organic chemistry, the anomeric effect or Edward-Lemieux
effect is a stereoelectronic effect that describes the tendency of
heteroatomic substituents adjacent to a heteroatom within a
cyclohexane ring to prefer the axial orientation instead of the
less hindered equatorial orientation that would be expected from
steric considerations.
This effect was originally observed in pyranose rings by J. T.
Edward in 1955; at that time, N.-J. Chii and R. U. Lemieux began to
study the anomerization equilibria of the fully acetylated
derivatives of several aldohexopyranoses. The term "anomeric
effect" was introduced in 1958.
The anomeric effect received its name from the term used to
designate the C-1 carbon of a pyranose, the anomeric carbon.
Isomers that differ only in the configuration at the anomeric
carbon are called anomers.