Assertion : Rotation about C = C is restricted.
Reason : Electron charge cloud of the `pi` bond is located above and below the plane of bonding atoms.

Options

A. If both (A) and (R ) are correct and (R ) is the correct explanation of (A)
B. If both (A) and (R ) are correct, but (R ) is not the correct explanation of (A)
C. If (A) is correct, but (R ) is incorrect
D. If both (A) and (R ) are incorrect

Answer

B

Explanation

In a `pi`-bond formation, parallel orientation of the two p-orbitals on adjacent atoms is necessary for proper sideways overlap. The p-orbitals are mutually parallel and both the p-orbitals are perpendicular to the plane of the molecule. Rotation of one `CH_(2)` fragment with respect to other, interferes with maximum overlap of p-orbitals and hence such rotation is restricted.