객관식
In the context of Hückel’s rule, which of the following species is aromatic?
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18. Aromaticity
Aromaticity
객관식
Which of the following cyclic species is NOT aromatic (i.e., not planar and fully conjugated with electrons)?
A
Cyclopentadienyl anion ()
B
Cyclobutadiene
C
Benzene
D
Pyridine
검증된 단계별 안내1
Step 1: Recall the criteria for aromaticity: a molecule must be cyclic, planar, fully conjugated (p orbitals overlapping continuously), and contain a total of \(4n + 2\) π electrons, where \(n\) is a non-negative integer (Hückel's rule).
Step 2: Analyze each species for these criteria. First, check if the molecule is cyclic and planar, allowing for continuous overlap of p orbitals (full conjugation).
Step 3: Count the number of π electrons in each species. For example, benzene has 6 π electrons, which fits \(4n + 2\) with \(n=1\); the cyclopentadienyl anion has 6 π electrons as well; pyridine is similar to benzene with 6 π electrons.
Step 4: Examine cyclobutadiene, which is cyclic and conjugated but has 4 π electrons. This fits the \$4n\( rule (with \)n=1$), not the \(4n + 2\) rule, indicating antiaromaticity or non-aromaticity due to instability and possible non-planarity.
Step 5: Conclude that cyclobutadiene is NOT aromatic because it does not satisfy Hückel's rule and is typically not planar and fully conjugated in its stable form, unlike the other species listed.
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