Question

Considering cyclobutane to be planar, the number of planes of symmetry in the following compound is _______ (in integer).

Hint:

Start with the parent ring’s symmetry (planar cyclobutane has multiple mirror planes) and then remove any plane that does not map substituents onto identical positions.

Answer 1

Treat the cyclobutane ring as a planar square with two identical Me substituents on adjacent ring carbons. This substitution pattern retains only one mirror plane: the plane that bisects the C–C bond connecting the substituted carbons and the opposite bond (passing through the ring center). The second mirror plane of unsubstituted planar cyclobutane is lost due to unequal substitution across that plane.
Therefore, the molecule has exactly one plane of symmetry.