[Bemanos]

Hi ,can someone explain to me (in a practical way if possible) how to find if a molecule has an σh σv or σd symmetry operation?

-thanks in advance

[Corribus]

Let's start with the obvious. Do you know how to find a principal axis and mirror planes?

[Bemanos]

yes

[Corribus]

So then, find the principle axis and then look for mirror planes. If there is a mirror plane that contains the principle axis, it is a σ_v (or σ_d). If there is a mirror plane that is perpendicular to the principle axis, this is a σ_h. The distinction between the vertical and dihedral planes is that the latter bisects two rotation axes that are both perpendicular to the principle axis. The dihedral mirror planes are special types of vertical mirror planes. They are typically observed in conjunction with horizontal mirror planes, in molecules such as benzene.