Can you please explain D and L designation for ENANTIOMERS?

Answer 1

The term D and L orginally came from a chemist that found that different molecules of tartaric acid rotated light in different directions. Both types of molecules were identical in their chemical make-up one molecule would rotate polarized light to the right and on would rotate polarilzed light to the left. If you had an equal amount of both molecules light would not rotate at all. This opened the branch of chemistry called stereochemistry. Molecules with the same formula but can be considered left and right hand molecules based on the light rotation. D is dextrorotary and rotates light to the right, the L is levorotary and rotates light to the left.

Answer 2

Dextarotary

and

Levarotary

Not sure on the spelling but this indicates the way that the enantiomers rotate polarized light.

Opposite enantiomers rotate light in opposite directions.

Answer 3

D- means H-C-OH at the second-from the bottom carbon of a simple sugar. L- means HO-C-H. In amino acids, D- means H2N-C-H, if COOH is at the top of the C, and the rest of the amino acid is at the bottom. D- and L- describe configurations of atoms in space. There are lower-case letters, d- and l-, sometimes given as (+)- and (-)- to denote the rotation of the plane of plane-polarized light to right (dextrorotatory) or left (levorotatory). Configuration has nothing to do with rotation.