Question

What effect do double and triple bonds have on rotation within molecules compared to single bonds?

Answer 1

The presence of the double and triple bond does not allow the molecule to rotate since double and triple bond contains Pi bonds where the electron density lies above and below the plane of the bonded atoms and for a molecule to rotate these pi bonds must break and therefore the rotation is restricted in molecules containing double and triple bonds. In case of single bonds, these are formed by the side overlap of the atomic orbitals which can be rotated without any difficulty and thus single bonds are free to rotate.