Chapter 24.2, Problem 6CC

(a)

Interpretation Introduction

Interpretation:

For the four stereo isomeric aldotetroses, the pair of enantiomers and stereo descriptors is needed to be drawn.

Concept introduction:

• Aldoses are monosaccharides, which contains Aldehyde group.
• The naming of monosaccharides,
  • Prefix: aldo or keto indicates whether the monosaccharide is containing aldehyde or ketone group.
  • Suffix: ose indicates the carbohydrates
  • Root word: indicate the number of carbons.
• The stereo-descriptor used for monosaccharides is D or L. it is based on the dextrorotatory glyceraldehyde or levorotatory glyceraldehyde.

  

  The stereo-descriptor for other carbohydrates of having more than one chiral center will be evaluated by the location of –OH group (right or left) of farthest chiral carbon from the carbonyl group. Such as,

  If the –OH group is located in right side then, the carbohydrate is a D-sugar.

  If the –OH group is located in left side then, the carbohydrate is a L-sugar.

• Enantiomers are non-super imposable mirror images of each other.

To determine: the structures of pair of enantiomers of stereo isomeric aldotetroses.

(b)

Interpretation Introduction

Interpretation:

For the four stereo isomeric aldotetroses, the pair of enantiomers and stereo descriptors is needed to be drawn.

Concept introduction:

• Aldoses are monosaccharides, which contains Aldehyde group.
• The naming of monosaccharides,
  • Prefix: aldo or keto indicates whether the monosaccharide is containing aldehyde or ketone group.
  • Suffix: ose indicates the carbohydrates
  • Root word: indicate the number of carbons.
• The stereo-descriptor used for monosaccharides is D or L. it is based on the dextrorotatory glyceraldehyde or levorotatory glyceraldehyde.

  

  The stereo-descriptor for other carbohydrates of having more than one chiral center will be evaluated by the location of –OH group (right or left) of farthest chiral carbon from the carbonyl group. Such as,

  If the –OH group is located in right side then, the carbohydrate is a D-sugar.

  If the –OH group is located in left side then, the carbohydrate is a L-sugar.

• Enantiomers are non-super imposable mirror images of each other.

To identify: the D sugar and L sugar from the four structures of stereo isomeric aldotetroses.