Question

For each structure shown below, determine the number of pi electrons. Indicate whether the structure is aromatic,

Answer 1

Concepts and reason

The concept used in solving the given problem is the Huckel’s rule and estimation of lone pairs and the ${\rm{\pi }}$ bonds. The presence of ${\rm{\pi }}$ -bonds and lone pair of the electrons helps in determining the number of electrons and the Huckel’s rule help in the determination of the aromaticity of the compound.

Fundamentals

A ${\rm{\pi }}$ -bond consists of $2$ ${\rm{\pi }}$ -electrons and two electrons are present in a lone pair of electrons.

• Aromatic compounds:

1.It should follow Huckel’s rule, that is, the compound should contain $\left( {4n + 2} \right)\pi$ electrons in cyclic conjugation where is a whole number.

2.It should be planar.

3.It should be cyclic.

4.It should have continuous delocalization of electrons.

• Antiaromatic compounds do not follow $\left( {4n + 2} \right)\pi$ electrons instead they have $\left( {4n} \right)\pi$ electrons in cyclic conjugation.

• Non-aromatic compounds are the one which are not planar and neither belongs to aromatic nor antiaromatic compounds.

The number of ${\rm{\pi }}$ (pi) electrons present in the structure given below is $4$ .

Furthermore, the given compound is antiaromatic in nature.

The number of ${\rm{\pi }}$ -electrons present in the structure given below is $6$ .

Furthermore, the given compound is aromatic in nature.

The number of ${\rm{\pi }}$ -electrons present in the structure given below is $6$ .

Furthermore, the given compound is aromatic in nature.

Ans:

The compound mentioned below has $4$ ${\rm{\pi }}$ -electrons present and is nonaromatic in nature.

The compound mentioned below has $6$ ${\rm{\pi }}$ -electrons present and is aromatic in nature.

The compound mentioned below has $6$ ${\rm{\pi }}$ -electrons present and is aromatic in nature.