Import Question JSON

$\text{Hint: Use Huckel's Rule of aromaticity.}$ $\text{Step 1: There are four criteria for aromaticity as follows:}$ $\text{(a) The molecule is cyclic (a ring of atoms)}$ $\text{(b) The molecule is planar (all atoms in the molecule lie in the same plane)}$ $\text{(c) The molecule is fully conjugated (p orbitals at every atom in the ring)}$ $\text{(d) The molecule has } (4n + 2) \pi \text{ electrons (n=0 or any positive integer)}$ $\text{Step 2:}$ $\text{Among the given compounds, only phenanthrene is an aromatic compound. Other compounds have } sp^3 \text{ hybridized carbon atoms which makes them non-aromatic.}$ $\text{Phenanthrene is another polycyclic aromatic hydrocarbon but unlike anthracene, its three benzene rings are fused in an angular arrangement.}$ $\text{Although phenanthrene's structure is slightly non-planar due to steric interactions between hydrogen atoms at the fusion points of the rings, it is still sufficiently planar for the } \pi \text{-electrons to be delocalized across the molecule.}$ $\text{Although phenanthrene is slightly less stable than benzene due to the strain introduced by the angular fusion of the rings. The slight non-planarity of phenanthrene does not completely disrupt the conjugation of } \pi \text{-electrons. The delocalization of } \pi \text{-electrons still occurs, making the molecule aromatic.}$ $\text{Phenanthrene is more stable than anthracene due to the larger stability of the } \pi \text{-system of the former, which is more aromatic.}$ $\text{Hence, option 2 is the correct answer.}$