The planar <para-quinone> framework has three mutually perpendicular twofold axes, inversion through its centre, and the associated mirror planes. With $x$ horizontal, $y$ along the two C=O bonds and $z$ perpendicular to the molecule, it belongs to the <D2h point group>, $\boxed{D_{2h}}$.

Solution

Past exam of the chemistry A course of the University of Cambridge / 2025 / Paper 1 / A5 / a / Solution

 Solution (source code)