Which of the following compounds is aromatic?

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

Answer: (C)

Verified step by step guidance

1. Recall the criteria for aromaticity: a compound 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, ...).
2. Analyze each compound to determine if it meets these criteria. First, check if the compound is cyclic and planar. For example, benzene is cyclic and planar, while cyclooctatetraene adopts a non-planar 'tub' shape, which affects conjugation.
3. Count the number of π electrons in each compound. Each double bond contributes 2 π electrons. For instance, benzene has 3 double bonds, so it has 6 π electrons.
4. Apply Hückel's rule to the π electron count. For benzene, 6 π electrons fit the formula (4n + 2) with n=1, indicating aromaticity. For cyclobutadiene, 4 π electrons correspond to n=0.5, which does not satisfy the rule, making it antiaromatic or non-aromatic depending on geometry.
5. Conclude which compound is aromatic based on the above analysis. Benzene meets all criteria, while the others do not due to either geometry or electron count.