Which of the following are aromatic?
- B and D only
- A and C only
- C and D only
- A and B only
Answer
(1) B and D only
Solution
[figure]
A: two sp3 carbons (marked) break the cyclic conjugation, so A is non-aromatic
B: the benzene ring is planar with 6π electrons, so B (styrene) is aromatic
C: [10]annulene has 10π electrons, but its two inner H atoms clash and the ring is not planar, so C is non-aromatic
D: [14]annulene is cyclic and conjugated with 14 = (4n + 2) electrons (n = 3), so D is aromatic
Hence B and D only.
Answer: (1)