Which of the following compounds is aromatic?

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

Answer: (B)

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 check if it meets these criteria. Start with cyclohexane (C\6H\12): it is cyclic but saturated (no double bonds), so it has no π electrons and is not aromatic.
3. Next, consider benzene (C\6H\6): it is cyclic, planar, has alternating double bonds providing 6 π electrons, and 6 fits Hückel's rule with n=1 (4(1)+2=6). Thus, benzene is aromatic.
4. Examine cyclobutadiene (C\4H\4): it is cyclic and conjugated with 4 π electrons, but 4 does not satisfy Hückel's rule (4n+2 ≠ 4 for any integer n). Also, it is antiaromatic or non-aromatic due to instability.
5. Finally, look at cyclooctatetraene (C\8H\8): although it has 8 π electrons, it is not planar in its usual conformation, so it does not have continuous overlap of p orbitals and is not aromatic.