Question

For the structure below, determine the total number of Pi electrons and the number of Pi electrons delocalized in the ring. Indicate whether the compound is aromatic, nonaromatic, or antiaromatic. Assume the structure is planar.

For the structure below, determine the total number of ? electrons and the number of ? electrons delocalized in the ring. Indicate whether the compound is aromatic, nonaromatic, or antiaromatic. Assume the structure is planar.

Answer 1

Concepts and reason

The concept used in this problem is of aromaticity. The compounds which contain $4n + 2$ delocalized $\pi$ electrons are aromatic where, n is any whole number. Anti-aromatic compounds contain $4n$ delocalized $\pi$ electrons.

Fundamentals

One $\pi$ bond contains two $\pi$ electrons. A double bond contains one sigma bond and one $\pi$ bond. A triple bond contains one sigma bond and two $\pi$ bonds.

The total number of $\pi$ bonds is 8. Each bond contains two electrons. So, the number of $\pi$ electrons are 16.

Out of two $\pi$ bonds of one alkyne in structure, only electrons of one $\pi$ bond participate in delocalization. The delocalization is shown as follows:

Total 7 $\pi$ bonds participate in delocalization out of total 8. So, 14 $\pi$ electrons delocalize in the structure.

Total 7 $\pi$ bonds participate in delocalization out of total 8. So, 14 $\pi$ electrons delocalize in the structure.

When n is 3, $4n + 2$ would be 14. So, the compound is aromatic.

Ans:

Total number of $\pi$ electrons are 16.