I'm currently looking at a problem that asks about the structural relationship between the 4 nitrogens the caffeine molecule. I am asked to identify whether they are in perpendicular planar, coplanar, or inverted planar formations.
I'm am a bit lost as to how I should approach this problem. Should I look at hybridization (3 Ns are sp3, 1 N is sp2)? Or resonance (seems that all Ns are involved in resonance)? Or should I be concerned with sterics?
Lastly, what are some examples that might assume a perpendicular planar, coplanar, and inverted planar formation? I don't think I've ever seen such shapes before...
Would someone please point me to the right direction?