Which of the following is not an aromatic com | vedclass

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(B) To determine if a compound is aromatic,it must follow $H$ückel's rule: it must be cyclic,planar,fully conjugated,and have $(4n + 2) \pi$ electrons

Vedclass · Accepted Answer

Cyclopentadienyl cation $(C_5H_5^+)$

Vedclass · Answer

(B) To determine if a compound is aromatic,it must follow $H$ückel's rule: it must be cyclic,planar,fully conjugated,and have $(4n + 2) \pi$ electrons,where $n = 0, 1, 2, ...$ $A$. Cyclopentadienyl anion $(C_5H_5^-)$: It has $6 \pi$ electrons ($4 \pi$ from two double bonds + $2 \pi$ from the lone pair on the carbon atom with the negative charge). It follows $(4n + 2)$ rule with $n = 1$. Thus,it is aromatic.$B$. Cyclopentadienyl cation $(C_5H_5^+)$: It has $4 \pi$ electrons. It follows $4n$ rule with $n = 1$. Thus,it is anti-aromatic.$C$. Cyclopropenyl cation $(C_3H_3^+)$: It has $2 \pi$ electrons. It follows $(4n + 2)$ rule with $n = 0$. Thus,it is aromatic.$D$. Cycloheptatrienyl cation $(C_7H_7^+)$: It has $6 \pi$ electrons. It follows $(4n + 2)$ rule with $n = 1$. Thus,it is aromatic.Therefore,the cyclopentadienyl cation is not aromatic (it is anti-aromatic).

Which of the following is not an aromatic compound?

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