Classify the following compounds as aromatic, antiaromatic, or nonaromatic

(a)

(b)

(c)

(d)

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.

(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.