Question

Stereoisomers,' . which can be interconverted simply by rotation about- sigma bonds, are conformational isomers' while those, which can be converted only by breaking and remaking of bonds and not simply by rotation, are called configurational isomers. The angle between C-C and C-H bonds on adjacent carbon atoms in any conformation is' called· dihedral· angle.
The cyclic compounds most commonly found in nature containing 'six membered rings can exist in a conformation that is almost Completely free of strain. The most stable conformation of cyclohexane.is chair form, According to Bayer strain theory, the greater deviation from the normal tetrahedral angle;. greater is the angle strain or torsional strain and hence lesser is the stability of the cycloalkane.
Dihedral angle in staggered and eclipsed conformations are:

1. and    
2. and    
3. ,    
4. ,