Question

What is the difference between steric and torsional strain?

Answer 1

Hint :Steric strain is caused because the bulky substituents occupy large space around a carbon atom which makes the substituents come close to each other, so their electrons will repel. Torsional strain is caused because of the repulsion of the electrons forming the bonds of two adjacent carbon atoms. While drawing Newman’s projection in the case of eclipsed and staggered, we consider the torsional strain.

Complete Step By Step Answer:
As the bulky substituents occupy large space around a carbon atom, it results in getting the substituents closer to each other which makes the electrons to repel and this strain is called steric strain. Whereas the torsional strain results due to the repulsion of the electrons forming the bonds of two adjacent carbon atoms. In the case of eclipsed conformation, the steric strain is higher because the bonds are in the closest position to each other. Steric strain is the least in the case of staggered because the bonds are the farthest apart. An example of torsional strain is while drawing the Newman projections of butane, the torsional strain is the one which makes the anti conformation more favourable than the gauche conformation. The increase in potential energy of a molecule due to repulsion between electrons in atoms that are not directly bonded to each other is the steric strain.

Note :
The main difference between steric and torsional strain is that steric strain cannot be reduced by rotating the molecule around a bond whereas torsional strain can be reduced by rotating the molecule around a bond.