Q37E - Organic Chemistry (Mcmurry)

Question

Which of the following pairs of structures represent the same enantiomer, and which represent different enantiomers?

Step-by-Step Solution

Answer

Part (a) structures are enantiomers

Part (b) structures are identical

Part (c) structures are identical

Part (d) structures are identical

Step 1:Enantiomers

Enantiomers are the pair of “optical isomers’’ having the opposite alpha value $\left(\alpha \right)$, representing the optical rotation.

 

Enantiomers are identified by experimenting with the help of plane-polarized light (PPL).

Step 2: Pair (a) structures

Enantiomers are the mirror images of each other,and that is non-superimposable on each other.

 

 The part (a) structures are of the different configurations, s-configuration, and R-configuration, around the chiral center, and there is the absence of symmetry in the molecule.

• Lack of center of symmetry
• Lack of plane of symmetry

Therefore both structures of the part (a) are enantiomers.

Enantiomers (a)

Step 3: Pair (b) structures

Enantiomers are the mirror images of each other, and that is non-superimposable on each other.

 The part (b) structures are of the same configuration,s-configuration, around the chiral center; thus, the molecule has a plane of symmetry.

Therefore both structures of part (b) are identical.

Identical (b)

Step 4: Pair (c) structures

Enantiomers are the mirror images of each other,and that is non-superimposable on each other.

 

 The part (c) structures are of the same configuration,R-configuration, around the chiral center; thus, the molecule has a plane of symmetry.

Therefore both structures of part (c) are identical.

Identical (c)

Step 5: Pair (d) structures

Enantiomers are the mirror images of each other,and that is non-superimposable on each other.

 

The part (d) structures are of the same configuration, s-configuration, around the chiral center; thus, the molecule has a plane of symmetry.

Therefore both structures of part (d) are identical.

Identical (d)