Compound A

In the following compound (Pyrene) why isn't Huckle's (4n+2) rule applicable? I do know it is applicable to only mono-cyclic ring systems but what changes when there are more than 3 fused rings?


A similar question has been posted previously but that doesn't mention as to why only the peripheral bonds are to be considered.

  • $\begingroup$ @thewitness please do see the edit $\endgroup$
    – J_B892
    Nov 7, 2018 at 12:01
  • $\begingroup$ That is because the double bond in the centre doesn't take part in resonance. It is quite similar to the lone pair in pyridine and the "second" lone pair in furan where we don't consider them as a part of π electrons while applying Haeckel's Rule. We require a complete conjunction to classify a compound into aromatic or non aromatic. In case there is no complete conjugation, it is non aromatic. $\endgroup$
    – user600016
    Nov 7, 2018 at 12:24
  • $\begingroup$ So in any of such compounds the double bonds not along the periphery do not involve in resonance? $\endgroup$
    – J_B892
    Nov 7, 2018 at 12:26
  • $\begingroup$ It depends on whether or not it can participate in resonance. $\endgroup$
    – user600016
    Nov 7, 2018 at 12:29
  • $\begingroup$ So the peripheral rule isn't applicable everywhere? $\endgroup$
    – J_B892
    Nov 7, 2018 at 12:37