Question: 82. The products A and B obtained in the following reactions, respectively, are
3 \mathrm{ROH}+\mathrm{PCl}_{3} \rightarrow 3 \mathrm{RCl}+\mathrm{A} \mathrm{ROH}+\mathrm{PCl}_{5} \rightarrow \mathrm{RCl}+\mathrm{HCl}+\mathrm{B}(1) \mathrm{POCl}_{3} and \mathrm{H}_{3} \mathrm{PO}_{3}
(2) \mathrm{POCl}_{3} and \mathrm{H}_{3} \mathrm{PO}_{4}
(3) \mathrm{H}_{3} \mathrm{PO}_{4} and \mathrm{POCl}_{3}
(4) \mathrm{H}_{3} \mathrm{PO}_{3} and \mathrm{POCl}_{3}
Answer: Option (4)
Explanation:
Phosphorus trichloride reacts with alcohols by replacing the hydroxyl group with chlorine.
In the reaction with \mathrm{PCl}_{3},
three molecules of alcohol react with one molecule of \mathrm{PCl}_{3}
to form three molecules of alkyl chloride.
The phosphorus-containing product formed in this reaction is phosphorous acid,
\mathrm{H}_{3}\mathrm{PO}_{3}.
Hence, in the first reaction, product A is \mathrm{H}_{3}\mathrm{PO}_{3}.
Phosphorus pentachloride reacts with alcohols to give alkyl chloride along with hydrogen chloride.
The phosphorus-containing product formed in this reaction is phosphoryl chloride,
\mathrm{POCl}_{3}.
Hence, in the second reaction, product B is \mathrm{POCl}_{3}.
Therefore, the correct pair of products A and B is \mathrm{H}_{3} \mathrm{PO}_{3}
and \mathrm{POCl}_{3}.