11th Class Chemistry Hydrocarbons

  • question_answer 76)   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
     


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