2023 HydrocarbonsAromaticity – Huckel's Rule Hard Question 1 of 2 in Aromaticity – Huckel's Rule

Consider the following compounds/species: The number of compounds/species which obey Huckel's rule is _______.

Consider the following compounds/species:

The number of compounds/species which obey Huckel's rule is _______.
A 5
B 4
C 6
D 2

The answer is B.

Solution

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.

Concept counting aromatic species

Aromaticity – Huckel's Rule in past papers

2 questions from this chapter have appeared across 2 exam years.