Problem
15-4
Pyridine has an aromatic sextet of electrons.
Problem
15-5
Cyclodecapentaene is not flat because of steric interactions.
Problem
15-6
All C – C bonds are equivalent; one resonance line in both 1H and 13C NMR spectra.
Problem
15-7
The cyclooctatetraenyl dianion is aromatic (ten π electrons) and flat.
Problem
15-10
The thiazolium ring has six π electrons.
Problem
15-11
Yes, it's aromatic.
Problem
15-12
The three nitrogens in double bonds each contribute one; the remaining nitrogen contributes two.