Q54 E_d. - Organic Chemistry (Mcmurry)

Question

Ribose, an essential part of ribonucleic acid (RNA), has the following structure:

(a) How many chirality centers does ribose have? Identify them.

(b) How many stereoisomers of ribose are there?

(c) Draw the structure of the enantiomer of ribose.

(d) Draw the structure of a diastereomer of ribose.

Step-by-Step Solution

Answer

(d) There are a total of six diastereomers of ribose, and the structures are shown below.

Diastereomers

Diastereomers are the stereoisomers that have non-identical configurations and look different at one or more than one stereocenters. Only one chiral carbon is needed to change its configuration for a molecule to call a diastereomer.

The structure of the diastereomer of ribose

(d) The structure of the diastereomer of ribose is drawn by taking the mirror image of the given ribose. The groups above the plane go below, and those below the plane go above.

                                                    Diastereomers of ribose