Which of the following is nonaromatic in natu | vedclass

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(A) To determine the aromaticity of a compound,we use $H$ückel's rule,which states that a planar,cyclic,fully conjugated system with $(4n+2) \pi$ elec

Vedclass · Accepted Answer

Pyrrole cation $(C_4H_6N^+)$

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(A) To determine the aromaticity of a compound,we use $H$ückel's rule,which states that a planar,cyclic,fully conjugated system with $(4n+2) \pi$ electrons is aromatic.$A$. Pyrrole cation $(C_4H_6N^+)$: The nitrogen atom is $sp^3$ hybridized because it is bonded to four atoms (two carbons and two hydrogens). Since it is not $sp^2$ hybridized,the ring is not fully conjugated and thus it is nonaromatic.$B$. Benzene $(C_6H_6)$: It is a planar,cyclic,fully conjugated system with $6 \pi$ electrons $(n=1)$,so it is aromatic.$C$. Cyclopentadienyl cation $(C_5H_5^+)$: It is a planar,cyclic,fully conjugated system with $4 \pi$ electrons ($n=1$ in $4n$ rule),so it is antiaromatic.$D$. Cyclopropenyl cation $(C_3H_3^+)$: It is a planar,cyclic,fully conjugated system with $2 \pi$ electrons $(n=0)$,so it is aromatic.Therefore,the pyrrole cation is nonaromatic.

Which of the following is nonaromatic in nature?

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