The products A and B obtained in the following reactions, respectively, are: $3\mathrm{ROH}+\mathrm{PCl}{}_3\to 3\mathrm{RCl}+\mathrm{A}$ $\mathrm{ROH}+\mathrm{PCl}{}_5\to \mathrm{RCl}+\mathrm{HCl}+\mathrm{B}$

Solution & Explanation

\textbf{Answer:} (C) $\mathrm{H}{}_3\mathrm{PO}{}_3$ and $\mathrm{POCl}{}_3$ \textbf{Solution:} With $\mathrm{PCl}{}_3$, an alcohol is converted to the alkyl chloride and the phosphorus by-product is phosphorous acid: $3\mathrm{ROH}+\mathrm{PCl}{}_3\to 3\mathrm{RCl}+\mathrm{H}{}_3\mathrm{PO}{}_3$, so A is $\mathrm{H}{}_3\mathrm{PO}{}_3$. With $\mathrm{PCl}{}_5$, the by-products are $\mathrm{HCl}$ and phosphoryl chloride: $\mathrm{ROH}+\mathrm{PCl}{}_5\to \mathrm{RCl}+\mathrm{HCl}+\mathrm{POCl}{}_3$, so B is $\mathrm{POCl}{}_3$.