I am trying to learn how to determine if a molecule is aromatic, antiaromatic, or neither, by counting the number of electrons in the pi system. When oxygen has two lone pairs, how do I determine how many lone pairs participate in the aromaticity. In a problem set, one examples says one lone pair participates, but another example says no lone pairs participate. Both had oxygens with two lone pairs and two sigma bonds, I do not understand why it's different?
Should one exclude counting oxygen's lone pairs in the pi system if it will make the compound aromatic? Or if it will prevent it from being antiaromatic? This is the only reasoning I can think of.
Also I am so not sure if the second example would be considered antiaromatic or neither?