Explanation:
\({\text{Cl - (C}}{{\text{H}}_{\text{2}}}{{\text{)}}_{\text{4}}}{\text{ - Cl}}\xrightarrow{{{\text{KCN}}}}{\text{NC - (C}}{{\text{H}}_{\text{2}}}{{\text{)}}_{\text{4}}}{\text{ - CN}}\)
\(\xrightarrow{{{\text{LAH}}}}\mathop {\mathop {{{\text{H}}_{\text{2}}}{\text{N - C}}{{\text{H}}_{\text{2}}}{\text{ - (C}}{{\text{H}}_{\text{2}}}{{\text{)}}_{\text{4}}}{\text{ - C}}{{\text{H}}_{\text{2}}}{\text{ - N}}{{\text{H}}_{\text{2}}}}\limits_{{\text{Hexamethylene}}\,{\mkern 1mu} {\text{dia}}\,{\text{mine}}} }\limits_{{\text{(Monomer}}{\mkern 1mu} \,{\text{of}}\,{\mkern 1mu} {\text{Nylon}}{\mkern 1mu} {\text{ - }}\,{\mkern 1mu} {\text{6,}}{\mkern 1mu} {\text{6)}}} \)