Question

The order of stability of aromatic hydrocarbons given below is

• A. A < D < B < C
• B. D < A < B < C
• C. B < C < D < A
• D. A < D < B < C

Answer 1

Answer: (D)

Stability of benzene and polycyclic aromatic compounds is determined by resonance energy per ring. Benzene has resonance energy of $36kcal/mol$ per ring, naphthalene has $30.3$ kcal/mol, phenanthrene has $30.5kcal/mol$ and anthracene has $28kcal/mol$ resonance energy per ring. Stability of aromatic compound is directly proportional to resonance energy per ring. Hence, order of stability :

Benzene $(A)>$ phenanthrene $(D)>$ naphthalene $(B)>$ anthracene $(C)$