Sodium Benzoate $\underset{\mathrm{\Delta }}{\overset{\mathrm{NaOH}+\mathrm{CaO}}{\to }}\mathrm{A} \underset{\mathrm{Anh}.{\mathrm{AlCl}}_3}{\overset{{\mathrm{CH}}_3\mathrm{Cl}}{\to }}\mathrm{B}\underset{\text{ (ii) }{\mathrm{H}}_3{\mathrm{O}}^{+}}{\overset{\text{ (i) }{\mathrm{CrO}}_2{\mathrm{Cl}}_2/{\mathrm{CS}}_2}{\to }}\mathrm{C}$
In the reaction sequence, conversion of B to C is known as

$$\begin{gathered} \underset{\mathrm{Sodium} \mathrm{benzoate}}{{\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{COO}}^{-}{\mathrm{Na}}^{+}}\underset{\mathrm{\Delta }}{\overset{\mathrm{NaOH}+\mathrm{CaO}}{\to }}\underset{\mathrm{A}}{{\mathrm{C}}_6{\mathrm{H}}_6} \\ \underset{\mathrm{A}}{{\mathrm{C}}_6{\mathrm{H}}_6}\underset{ \mathrm{B}}{\underset{\mathrm{Anh}.{\mathrm{AlCl}}_3}{\overset{{\mathrm{CH}}_3\mathrm{Cl}}{\to }}{\mathrm{C}}_6{\mathrm{H}}_5-{\mathrm{CH}}_3} \\ \underset{\mathrm{Etard} \mathrm{reaction}}{\underbrace{\underset{\mathrm{B}}{{\mathrm{C}}_6{\mathrm{H}}_5-{\mathrm{CH}}_3}\underset{\text{ (ii) }{\mathrm{H}}_3{\mathrm{O}}^{+}}{\overset{\text{ (i) }{\mathrm{CrO}}_2{\mathrm{Cl}}_2/{\mathrm{CS}}_2}{\to }}\underset{\mathrm{C}}{{\mathrm{C}}_6{\mathrm{H}}_5-\mathrm{CHO}}}} \end{gathered}$$