Compounds with several chiral centres may have configurations referred to as meso. Meso configurations arise when the molecule can adopt a configuration with an internal mirror plane. When this occurs, the mirror image of a molecule with an internal mirror plane is an identical configuration. Thus, even though the molecule may possess several chiral centres, they are reflection of each other (within the molecule) thus resulting in an achiral meso form. This occurs for example for tartaric acid (Figure 3.1). Because of this, tartaric acid only has three stereoisomers instead of four. It has the two chiral (R,R) and (S,S) enantiomers, and the meso form. Figure 3.1. Stereoisomers of tartaric acid. Given the information above on meso forms, how many different stereoisomers do compounds A to D (Figure 3.2) have? Figure 3.2. Structure of compounds A, B, C and D.
Compounds with several chiral centres may have configurations referred to as meso. Meso configurations arise when the molecule can adopt a configuration with an internal mirror plane. When this occurs, the mirror image of a molecule with an internal mirror plane is an identical configuration. Thus, even though the molecule may possess several chiral centres, they are reflection of each other (within the molecule) thus resulting in an achiral meso form.
This occurs for example for tartaric acid (Figure 3.1). Because of this, tartaric acid only has three stereoisomers instead of four. It has the two chiral (R,R) and (S,S) enantiomers, and the meso form.
Figure 3.1. Stereoisomers of tartaric acid.
Given the information above on meso forms, how many different stereoisomers do compounds A to D (Figure 3.2) have?
Figure 3.2. Structure of compounds A, B, C and D.
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