Reaction Product of Thionyl Chloride with White Phosphorus

When white phosphorus ($\text{P}_4$) reacts with thionyl chloride ($\text{SOCl}_2$), it undergoes a chlorination reaction to yield phosphorus trichloride ($\text{PCl}_3$), along with sulfur dioxide ($\text{SO}_2$) and disulfur dichloride ($\text{S}_2\text{Cl}_2$).

The balanced chemical equation for the reaction is: $\text{P}_4 + 8\text{SOCl}_2 \longrightarrow 4\text{PCl}_3 + 4\text{SO}_2 + 2\text{S}_2\text{Cl}_2$

Thus, the phosphorus-containing product formed in this reaction is phosphorus trichloride ($\text{PCl}_3$).

(Note: For comparison, reaction with sulfuryl chloride, $\text{SO}_2\text{Cl}_2$, yields phosphorus pentachloride, $\text{PCl}_5$).

Therefore, the correct option is (A).