Chemistry - Halogen Derivative Question with Solution | TestHub

An aromatic compound can follow Huckel's rule if it has $(4\mathrm{n}+2)\mathrm{\pi }$-electrons

where, $\mathrm{n}=$ integer $0,1,2,3,\dots$ etc.

Thus, 

(a) $\mathrm{n}=0; 4\times 0+2=2\mathrm{\pi }$

$\therefore$ follow Huckel's rule

(b) $\mathrm{n}=1;$ Number of $\mathrm{\pi }$-electrons $=6$

$\therefore$ follows Huckels rules.

(c) $\mathrm{n}=1;$ Number of $\mathrm{\pi }$-electrons $=6$

$\therefore$ follows Huckel's rule.

(d) $\mathrm{n}=1$, Number of $\mathrm{\pi }$-electrons $=8$

$(4\mathrm{n}+2=4\times 1+2=6)$

but this compound has $8$ electrons which distorts the plane and hence does not follows Huckel's rule.