Question

Benzocyclicbutene is aromatic or not

Answer 1

Non-aromatic

Answer 2

Solution Explanation:

1. Structure Consideration: Benzocyclobutene (often referred to when one sees “benzocyclicbutene”) consists of a benzene ring fused to a cyclobutene ring.

2. Aromaticity Criteria: For a ring to be aromatic, it must be cyclic, planar, fully conjugated, and contain (4n+2) π electrons (Hückel's rule).

3. Analysis for Benzocyclobutene:

   • The benzene ring has 6 π electrons and is aromatic.
   • The cyclobutene ring, however, has a four‐membered ring structure. It does not possess a fully conjugated continuous π system due to geometric constraints and does not satisfy the (4n+2) π electron rule when considered as part of an extended delocalization.
   • Thus, the π electrons are localized mainly in the benzene part and the cyclobutene does not contribute to an overall (4n+2) system.

4. Conclusion: Although the benzene portion is aromatic, the entire bicyclic system does not have a continuous conjugated pathway fulfilling Hückel’s criterion. Overall, benzocyclobutene is non‐aromatic.