$\mathop {{C_2}{H_5}OH}\limits_{\left( I \right)} $ $\mathop {{C_2}{H_5}Cl}\limits_{\left( {II} \right)} $ $\mathop {{C_2}{H_5}C{H_3}}\limits_{\left( {III} \right)} $ $\mathop {{C_2}{H_5}OC{H_3}}\limits_{\left( {IV} \right)} $
$C{H_3}C{H_2}OH\xrightarrow{{P + {I_2}}}A\xrightarrow{{Mg}}B\xrightarrow{{HCHO}}C\xrightarrow{{{H_2}O}}D$