Which of the following structures is aromatic?

• A. Cyclohexane ($C_6{H}_{12}$)
• B. Cyclobutadiene ($C_4{H}_4$)
• C. Benzene ($C_6{H}_6$)
• D. Cyclooctatetraene ($C_8{H}_8$)

Answer: (C)

Verified step by step guidance

1. 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.
2. Analyze Cyclohexane (C\6H\12): It is a saturated ring with only single bonds, so it has no π electrons and is not conjugated. Therefore, it is not aromatic.
3. Analyze Cyclobutadiene (C\4H\4): It is cyclic and conjugated with 4 π electrons, but 4 does not satisfy Hückel's rule (4n + 2). This makes it antiaromatic or non-aromatic due to instability.
4. Analyze Benzene (C\6H\6): It is cyclic, planar, fully conjugated with 6 π electrons. Since 6 fits Hückel's rule (4n + 2 with n=1), benzene is aromatic.
5. Analyze Cyclooctatetraene (C\8H\8): Although it has conjugated double bonds, it adopts a non-planar 'tub' shape to avoid antiaromaticity, so it is not aromatic.