• # question_answer Which of the following is not aromatic [Pb. CET 2000] A) Benzene B) Naphthalene C) Pyridine D) 1,3,5 heptatriene

A compound is said to be aromatic if it is planar and there is complete delocalization of $\pi$ electrons, which is only possilble if it is a conjugated cyclic system and number of electrons used in delocalization is $(4n+2)$. 1, 3, 5 heptatriene is not an aromatic compound because complete delocalization of $\pi$ electrons, is not possible in it.