Chemistry - GOC Question with Solution | TestHub

In triphenylene, all three outer rings are benzene sextets and the central ring has no extra double bond, so it has three intact benzene rings (about 108 kcal/mol). In phenanthrene only two intact benzene rings (72 kcal/mol) coexist with the central 9,10 double bond, so its total resonance energy (92 kcal/mol) is smaller than that of triphenylene.