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Hydrocarbons
Aromaticity – Huckel's Rule
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All Questions
2023 1 question
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Consider the following compounds/species:
The number of compounds/species which obey Huckel's rule is _______.Species with $(4n+2)\ \pi$ electrons that are cyclic, planar and conjugated obey Huckel's rule; four qualify.
According to Huckel rule, a compound/molecule is said to be aromatic if it is cyclic, planar, fully conjugated ($sp^2$ hybridised) and has $[4n+2]\ \pi$ electrons. The aromatic species have $10\pi$, $6\pi$, $2\pi$ and $14\pi$ electrons: all these are aromatic species according to Huckel rule.
2022 1 question
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Which compound amongst the following is not an aromatic compound?
Tropylium cation (6 $\pi$e), cyclopropenyl cation (2 $\pi$e) and cyclopentadienyl anion (6 $\pi$e) are planar, fully conjugated and obey Huckel's (4n + 2) rule – aromatic.
Cycloheptatriene has an $sp^3$ ($CH_2$) carbon, so it is not fully conjugated – non-aromatic.