Question

Which of the following is the correct order for the stability of anthracene and phenanthrene?

• A. Anthracene > Phenanthrene
• B. Anthracene < Phenanthrene
• C. Anthracene $\approx$ Phenanthrene
• D. Cannot be predicted

Answer 1

The correct option is A Anthracene > Phenanthrene

According to Fries' rule, the most stable form of the bonds of a polycyclic compound is that arrangement which has the maximum number of rings in the benzenoid form.

Number of benzenoid forms in anthracene = 6

Number of benzenoid forms in phenanthrene = 10

Since phenanthrene has more number of benzenoid rings than anthracene, hence according to Fries' rule, phenanthrene is more stable than anthracene.