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Carbohydrate Nomenclature

Anomer

Refers to the orientation of the hydroxyl group at the carbonyl carbon which arises due to internal condensation to for a 5- or 6-membered hemiacetal or hemiketal ring. Assignment of spatial position was originally made on the basis of optical rotation. A more accurate designation would indicate axial or equatorial as well as ring form.
Hint: "think alpha or beta."

Diastereoisomers

Compounds with identical formulas which have different spatial distributions of atoms. E.g.: galactose and mannose.

Enantiomorphs

Mirror images, DL pair, a special case of diastereoisomers. E.g.: D-glucose and L-glucose

Epimer

A term that is useful when discussing molecules with several centers of asymmetry. Refers to the configuration at a single center (others are usually the same). E.g.: glucose and galactose are C-4 epimers. This is yet another special case of diastereoisomers.

Equatorial

Bonds radiating in the general plane of the ring formed by the C-1, -2, -4, and -5 in a strainless 6-membered ring. Their angles to the plane is not quite 0 degrees.

Isomers

Any pair or group of compounds with the same empirical formula.

Meso form

An internally compensated structure that possesses a plane of symmetry. It is not optically active.

Rotamoer

Refers to a specific conformation for a compound having free or relatively free rotation about C-C bonds.

"D" and "L" forms

"D" (dextro = right) is any sugar derivable from D-glyceraldehyde by addition of more carbons directly below the aldehyde carbon.

"L" (levo = left) is the converse of "D".

(It is the convention in the drawing of these Fisher structures to think of the vertical bonds as going into the plane of the paper, and the horizontal bonds as coming out of the plane of the paper.)