A primary alkyl halide ${\mathrm{C}}_4{\mathrm{H}}_9\mathrm{Br}$ (A) reacted with alcoholic $\mathrm{KOH}$to give compound (B), Compound (B) is reacted with $\mathrm{HBr}$ to give (C) which is an isomer of (A). When (A) is reacted with sodium metal it gives compound (D), ${\mathrm{C}}_8{\mathrm{H}}_{18}$ which is different from the compound formed when n-butyl bromide is reacted with sodium. Give the structural formula of (A) and write the equations for all the reactions.

Account for the following statement:

Aryl halides are extremely less reactive towards nucleophilic substitution reactions.

Account for the following statement:

p-Nitrochlorobenzene and o, p-dinitrochlorobenzene undergo Nucleophilic Substitution reaction readily compared to chlorobenzene.

Explain how the following conversion is carried out:

Propene to Propanol

How the following conversion can be carried out?

Ethanol to but-1-yne

How the following conversion can be carried out?

$1$-Bromopropane to $2$-bromopropane

How the following conversion can be carried out?

Aniline to chlorobenzene