In electrophilic aromatic substitution reactions of chlorobenzene, the ortho/para-directing ability of chlorine is due to its:

$\mathrm{R}-\mathrm{Cl}+\mathrm{AgCN}\to \mathrm{A}\stackrel{ \mathrm{Reduction}}{⟶}\mathrm{B}$

$\mathrm{A}$ and $\mathrm{B}$, respectively are

In ${\mathrm{S}}_{\mathrm{N}}1$ reaction, the racemisation takes place. It is due to:

Describe the following reaction.