Question

Designate whether each of the following compounds is aromatic or not aromatic.

• A. e, g aromatic and a, b, c, d, f, h not aromatic
• B. b, e, f, g aromatic and a, c, d, h not aromatic
• C. a, b, c, d aromatic and e, f, g, h not aromatic
• D. a, c, d, e, h aromatic and b, f, g not aromatic

Hint:

\textbf{Huckel's Rule for Aromaticity:} \begin{itemize} \item Cyclic, planar molecule \item Fully conjugated $\pi$-system \item Contains 4n+2 $\pi$ electrons (n=0,1,2...) \end{itemize}

Answer 1

The Correct Option is D

Aromatic compounds (follow Huckel's rule):
(a) Cyclic, planar, conjugated with 6$\pi$ electrons (4n+2 where n=1)
(c) Cyclic, planar, conjugated with 6$\pi$ electrons
(d) Cyclic, planar, conjugated with 6$\pi$ electrons
(e) Cyclic, planar, conjugated with 6$\pi$ electrons
(h) Cyclic, planar, conjugated with 6$\pi$ electrons

Non-aromatic compounds:
(b) Not fully conjugated (sp$^3$ hybridized carbon breaks conjugation)
(f) Not planar (twisted structure prevents conjugation)
(g) Has 4$\pi$ electrons (doesn't satisfy 4n+2 rule)