The OH group of an alcohol or the COOH group of a carboxylic acid...

\mathrm{PCl}_5$on reaction with alcohol and carboxylic acid, replace$-\mathrm{OH}$group with$-\mathrm{Cl}$.$\begin{aligned}\mathrm{ROH}+\mathrm{PCl}_{5} \longrightarrow \mathrm{RCl}& + \mathrm{POCl} }_{3}+\mathrm{HCl}\\ \mathrm{RCOOH}+\mathrm{PCl}_{5} \longrightarrow & \mathrm{RCOCl}^2 \\ + & \mathrm{POCl}_{3}+\mathrm{HCl} \end{aligned}$$Related Theory$\mathrm{PCl}_5$ is used as a chlorinating agent and dehydrating agent for the synthesis of pesticides, phosphite antioxidants, plasticizers and stabilizers for plastic and elastomers etc