Which of the following compounds is aromatic?

• A. $C_6{H}_{12}$ (cyclohexane)
• B. $C_6{H}_6$ (benzene)
• C. $C_7{H}_{16}$ (heptane)
• D. $C_5{H}_{10}$ (cyclopentene)

Answer: (B)

Verified step by step guidance

1. Recall the definition of aromaticity: a compound is aromatic if it is cyclic, planar, fully conjugated (p orbitals at every atom in the ring), and follows Hückel's rule, which states it must have \$4n + 2\( π electrons, where \)n$ is a non-negative integer.
2. Examine each compound to check if it meets these criteria. Start with cyclohexane (\(C_6H_{12}\)): it is cyclic but saturated (only single 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 a conjugated π system, and contains 6 π electrons. Check if 6 fits Hückel's rule by solving \$4n + 2 = 6$.
4. Look at heptane (\(C_7H_{16}\)): it is an acyclic alkane (no ring), so it cannot be aromatic.
5. Finally, analyze cyclopentene (\(C_5H_{10}\)): it is cyclic and has one double bond, but it is not fully conjugated around the ring and does not have the required number of π electrons to satisfy Hückel's rule, so it is not aromatic.