An aromatic compound,among other things,should have a $\pi$-electron cloud containing $(4n + 2)$ electrons,where $n$ cannot be:

In which of the following reactions,$t$-butyl benzene is formed?
$1.$ Benzene $+ t$-butyl chloride $\xrightarrow{AlCl_3}$
$2.$ Benzene $+ (CH_3)_2C=CH_2 \xrightarrow{BF_3/HF}$
$3.$ Benzene $+ t$-butyl alcohol $\xrightarrow{H_2SO_4}$
$4.$ Benzene $+$ butanoyl chloride $\xrightarrow{AlCl_3}$ $\xrightarrow{Zn/Hg, HCl}$

Which of the following is not used in the Friedel-Crafts reaction?

Identify the correct method for the synthesis of the compound shown below from the following alternatives.

Which of the following is $NOT$ obtained by the fractional distillation of coal tar?

The number of $\pi$ electrons in the following molecule is: