Which one 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, cyclooctatetraene is cyclic but adopts a non-planar 'tub' shape, so it is not planar.
3. Count the number of π electrons in the ring for each compound. Each double bond contributes 2 π electrons. For example, 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 Hückel's rule, making it antiaromatic or non-aromatic depending on planarity.
5. Conclude which compound is aromatic by confirming it meets all criteria: cyclic, planar, fully conjugated, and has (4n + 2) π electrons. Among the options, benzene satisfies all these conditions and is aromatic.