From my understanding you can use huckles rule if you see all of the aromatic compounds are cyclic (joined) and conjugated then you can use 4n+2 (Huckles rule) so if you had a benzene ring with 3 double bonds you know that those three double bonds have 6 e- so you can put the equation like this:
6=4n+2
-2 -2
________
4=4n
4/4 =n
n = 1
so benzene is aromatic since n= a whole number
If there was a cyclic compound with 8 e- or 4 double bonds then the equation would be:
8=4n+2
-2 -2
________
6=4n
6/4 =n which is not a whole number, thus not aromatic. But use huckles rule only after ruling out the first two criteria:
1.) cyclic
2.) conjugation
Hope this helps,
DesiDentist
