question_answer 1)

  The ring systems having following characteristics are aromatic. (i) Planar ring containing conjugated \[\pi \]-bonds. (ii) Complete delocalization of the \[\pi \]-electrons in ring system, i.e., each atom in the ring has unhybridised p-orbital and (iii) Presence of (4n + 2)\[\pi \]-electrons in the ring where n is an integer (n = 0, 1, 2,......) (Huckel?s rule). Using this information classify the following compounds as aromatic/non aromatic.

Answer:

     

Compound	Planar ring	Complete delocalisation of \[\pi \]-electron	Huckel rule \[(4n+2)\pi \]electrons	Aromatic or Non-aromatic
(A)	Ö	Ö	(\[6\pi e\])Huckel rule obeyed	Aromatic
(B)	Ö	x Incomplete (Hybrid carbon)	(\[6\pi e\])	Non-aromatic
(C)	Ö	Ö	\[6\pi {{e}^{-}}\] (\[4\pi +2\] lone pair) Huckel rule verified	Aromatic
(D)	Ö	x (In-complete)	\[4\pi {{e}^{-}}\]	Non- aromatic
(E)	Ö	Ö	Ö	Aromatic
(F)	Ö	Ö	\[2\pi {{e}^{-}}\]Huckel rule verified for \[n=0\]	Aromatic
(G)	Ö	x	\[8\pi {{e}^{-}}\]Huckel rule not verified	Non- aromatic