Question

The aromatic compound/species with maximum number of x ^- electrons is

• A. Phenanthrene
• B. Naphthalene
• C. Cyclopentadienyl anion
• D. Cycloheptatrienyl cation

Answer 1

The Correct Option is A

The correct option is: (A): Phenanthrene.

Phenanthrene is indeed an aromatic compound with a substantial number of pi (π) electrons, which are often represented by "x" in this context. This property contributes to its aromaticity. Aromaticity is a concept in organic chemistry where a compound's molecular structure and electron arrangement fulfill specific criteria that lead to enhanced stability.

Phenanthrene is composed of three fused benzene rings, forming a polycyclic aromatic hydrocarbon. Each benzene ring contributes 6 π electrons to the aromatic system. The central benzene ring shares two of its π electrons with each adjacent ring. Thus, the total number of π electrons in phenanthrene's aromatic system is:

3 rings × 6 π electrons/ring = 18 π electrons

This 18 π electron system fulfills Hückel's rule for aromaticity, which states that for a ring to be aromatic, it must have 4n + 2 π electrons, where "n" is a whole number. In this case, when n is 4, the expression becomes 4n + 2 = 18, confirming the aromatic nature of phenanthrene.

In summary, phenanthrene possesses a maximum number of x - electrons (π electrons) which adds up to 18, satisfying the criteria for aromaticity according to Hückel's rule. This makes phenanthrene a suitable example of an aromatic compound with a significant electron delocalization and enhanced stability.