${\mathrm{C}}_2{\mathrm{H}}_2\underset{\begin{array}{l}\left(2\right){\mathrm{Cl}}_2/\mathrm{Anhy} {\mathrm{AlCl}}_3\\ \left(3\right)\mathrm{Mg}/\mathrm{Dry} \mathrm{ether}\\ \left(4\right)\mathrm{Dry} \mathrm{ice}/\mathrm{Dry}\mathrm{ether}\\ \left(5\right){\mathrm{H}}_3{\mathrm{O}}^{+}\end{array}}{\overset{\left(1\right)\mathrm{Red} \mathrm{hot} \mathrm{Fe}\mathrm{tube}}{\to }}\mathrm{Product}$

${\mathrm{C}}_2{\mathrm{H}}_2\stackrel{\mathrm{Red} \mathrm{hot} \mathrm{Fe} \mathrm{tube}}{\to }\mathrm{Benzene}\stackrel{{\mathrm{Cl}}_2/\mathrm{Anhy} {\mathrm{AlCl}}_3}{\to }{\mathrm{C}}_6{\mathrm{H}}_5\mathrm{Cl}\stackrel{\mathrm{Mg}/\mathrm{Dry} \mathrm{ether}}{\to }{\mathrm{C}}_6{\mathrm{H}}_5\mathrm{MgCl}\underset{{\mathrm{H}}_3{\mathrm{O}}^{+}}{\overset{ \mathrm{Dry} \mathrm{ice}/\mathrm{Dry}\mathrm{ether}}{\to }}{\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH}$