Imagine that you could hold two atoms that are bonded together, twist them, and not change the bond length. Would it be easier to twist (rotate) around a single σ bond or around a double σ plus π bond, or would they be the same?
it is easier to rotate and single bond rather than a double bond made of a sigma bond and pi bond
Explanation:
Rotation around a single bond happens easily but it is very limited around a double bond because of the overlapping electron cloud above and below the imaginary axis between the two atoms.
