MCAT Question A Day - 1/28/14 - Answer!

What is always true about an aromatic compound?

A. It contains only carbon and hydrogen atoms.

B. It undergoes addition reactions at room temperature.

C. It has delocalized electrons.

D. It has cis and trans isomers.

The correct answer is (C). Aromatic compounds have 4n+2 delocalized electrons. Nitrogen atoms, for example, can also participate in the ring, as in pyridine. Because the ring or rings are flat, cis and trans isomers do not exist. Aromatic compounds tend to undergo substitution reactions so as to maintain the stable aromatic character of the rings.

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