question_answer 57)

  Four structures are given in options (a) to (d). Examine them and select the aromatic structures : (a)                        (b)                 (c)     (d)

Answer:

    (a, c) Cyclopropenyl cation has completely delocalized\[2\pi \]- electrons. Therefore, it obey's Huckel rule and is aromatic. Diphenyl has two benzene rings each one of which is planar and has \[6\pi \]-electrons. Therefore, like benzene, it is also aromatic.