Clearly species 2 is the least ”homoaromatic” or “anthracene-like” and the most “annulene-like”. The fact that carbon 7 is the thermodynamically favored protonation site in 3 but not in 2 follows the same pattern and agrees with simple frontier MO theory considerations. Most likely, in 2 the increased strain in the central ring caused by protonation at positions 7 or 14 is not com- pensated by transannular stabilization as it is in the case ...