\b[<Pyrazine> belongs to $D_{2h}$], the <D2h point group>. With the printed axes, its three twofold axes are $x,y,z$; it also has an <inversion centre> and the three coordinate mirror planes. The nitrogen atoms occupy sites 1 and 4 on the $y$ axis. Interchanging carbon and nitrogen is not a <molecular symmetry operation>, so the sixfold <benzene> symmetry is lost.

Solution

Past exam of the chemistry A course of the University of Cambridge / 2023 / Paper 1 / A5 / b / i / Solution

 Solution (source code)