Which class of hydrocarbons includes benzene as the simplest member?

• A. Alcohol
• B. Aromatic
• C. Alkyne
• D. Ether

Answer: (B)

Aromaticity is the key idea here. Benzene is the classic example of an aromatic hydrocarbon—a planar, cyclic structure with electrons delocalized around the ring. That delocalized pi-electron cloud gives extra stability and a distinctive chemistry that sets aromatic compounds apart from other hydrocarbons. Benzene has six pi electrons, fitting the 4n+2 rule (n = 1), which explains why the ring is especially stable and like a single cooperative unit.

Other classes described aren’t purely hydrocarbons in the same sense, or involve different structural features. Alcohols and ethers contain oxygen functional groups, so they’re not classified simply as hydrocarbons. Alkynes are hydrocarbons with a carbon–carbon triple bond, not aromatic rings with delocalized electrons. So the class that includes benzene as its simplest member is the aromatic hydrocarbons.