Question

Classify the following compounds as aromatic, antiaromatic, or nonaromatic

(a)

(b)

(c)

(d)

Short answer

(a)

(b)

(c)

(d)

Step-by-step solution

Aromaticity

The aromaticity of any planar and nonplanar molecule can be identified by Huckel’s rule, i.e., (4n+2)where n represents the number of pi electrons.

Classification of the aromatic and nonaromatic molecule

(a)

The total number of pi electrons in conjugation is 14 which shows that the compound obeys the Huckel rule, i.e., (4n+2)pi electrons. In this case, the value of n is 3. Thus, the given structure is non-aromatic.

(b)

As one of the carbons in the given ring is sp³hybridized, therefore, p orbital is not available for the delocalization of the pi electrons. Hence, the given structure is non-aromatic.

(c)

The total number of pi electrons in conjugation is 14 which shows that the compound obeys the Huckel rule, that is (4n+2)electrons. In this case, the value of n is 3.

The structure is cyclic and planar in nature as all the carbons are sp³hybridized. Thus, the given structure is aromatic.

(d)

The total number of pi electrons in conjugation is 14 which shows that the compound obeys the Huckel rule, that is(4n+2)electrons. In this case, the value of n is 3.

The structure is cyclic and planar in nature as all the carbons are sp²hybridized. Thus, the given structure is aromatic.