Q.49. - Organic Chemistry

Question

Question: Label the sites of torsional and steric strain in each conformation.

a.

b.

c.

Step-by-Step Solution

Answer

Answer

a.

b. 

c. 

Step 1: Torsional strain

Torsional strain arises due to the great repulsion between two molecules or atoms that do not have a common bonded atom. Therefore, torsional strain arises in the eclipsed conformation.

Step 2: Steric strain

Steric strain occurs due to the overlapping of electron clouds of bulky groups (gauche interaction).

Step 3: Explanation

a. 

The molecule has no eclipsed conformation but gauche interaction. Therefore, it has a steric strain, not a torsional strain.

Steric strain sites

 

b.

 

The molecule has an eclipsed conformation,  not a gauche interaction (heavy groups interaction). Therefore, it only has a torsional strain.  

Torsional strain sites

 

c.

 

The molecule has an eclipsed conformation and heavy groups interaction. Therefore, it has both torsional and steric strains.  

Torsional strain and steric strain site