객관식
Which of the following compounds is ?
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18. Aromaticity
Aromaticity
객관식
Which of the following molecules is aromatic? 1. (benzene) 2. (cyclobutadiene) 3. (cyclopentadienyl anion) 4. (tropylium cation)
A
1 and 2 are aromatic; 3 and 4 are nonaromatic
B
1, 3, and 4 are aromatic; 2 is antiaromatic
C
Only 1 is aromatic; 2, 3, and 4 are nonaromatic
D
All four molecules are aromatic
검증된 단계별 안내1
Recall the criteria for aromaticity: a molecule must be cyclic, planar, fully conjugated (p orbitals at every atom in the ring), and follow Hückel's rule, which states it must have (4n + 2) π electrons, where n is a non-negative integer (0, 1, 2, ...).
Analyze benzene (C\_6H\_6): It is a six-membered ring with alternating double bonds, planar, fully conjugated, and has 6 π electrons. Since 6 fits Hückel's rule (4n + 2 = 6 when n=1), benzene is aromatic.
Analyze cyclobutadiene (C\_4H\_4): It is a four-membered ring with 4 π electrons. Although it is cyclic and conjugated, 4 π electrons fit the 4n rule (n=1), which makes it antiaromatic if planar. Typically, cyclobutadiene is antiaromatic due to this electron count and planarity.
Analyze cyclopentadienyl anion (C\_5H\_5\^-): This five-membered ring has 6 π electrons (4 from double bonds plus 2 from the negative charge). It is cyclic, planar, and fully conjugated. Since 6 π electrons satisfy Hückel's rule, it is aromatic.
Analyze tropylium cation (C\_7H\_7\^+): This seven-membered ring cation has 6 π electrons (from three double bonds, with the positive charge removing one electron). It is cyclic, planar, and fully conjugated. With 6 π electrons, it satisfies Hückel's rule and is aromatic.
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