Chapter 20.3, Problem 4P

a)

Interpretation Introduction

Interpretation:

Whether D-erythrose and L-erythose are enantiomers or diastereomers has to be stated.

Concept Introduction:

Enantiomers are the compounds with same chemical formula.  These are known as optical isomers.  Enantiomers are basically stereo-isomers of the same compound.  Two compounds are called enantiomers of each other if these are formed a non-superimposable mirror images.

Diastereomers are also the compounds with the same chemical formula.  These are also the types of stereo-isomers.  Two compounds are called diastereomers of each other if both the compounds have different configuration at the one or more (not all) equivalent stereo centers.  These are not mirror images of each other.

b)

Interpretation Introduction

Interpretation:

Whether L-erythrose and L-threose, enantiomers or diastereomers are to be stated.

Concept Introduction:

Enantiomers are the compounds with same chemical formula.  These are known as optical isomers.  Enantiomers are basically stereo-isomers of the same compound. Two compounds are called enantiomers of each other if these are formed a non-superimposable mirror images.

Diastereomers are also the compounds with the same chemical formula.  These are also the types of stereo-isomers.  Two compounds are called diastereomers of each other if both the compounds have different configuration at the one or more (not all) equivalent stereo centers.  These are not mirror images of each other.