Conformations, definition

This conformer definition is maintained even in three-membered heterocyclic derivatives, although the presence of one heteroatom alters the ring symmetry. Location of the angle 0 for the s-cis and s-trans conformers is a priori not feasible. 

See Appendix under Carbohydrate Conformational Nomenclature for conformational definitions. The Ci conformation is the usual one as is found for both diastereomers of D-glucose (shown) where the terminal —CH2OH group is equatorial. 

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