Question

Reaction of thionyl chloride with white phosphorus forms a compound [A], which on hydrolysis gives [B], a dibasic acid $[ A ]$ and $[ B ]$ are respectively

• A. $P _4 O _6$ and $H _3 PO _3$
• B. $PCl _5$ and $H _3 PO _4$
• C. $PCl _3$ and $H _3 PO _3$
• D. $POCl _3$ and $H _3 PO _4$

Answer 1

The Correct Option is C

The reaction proceeds as follows: 1. Step 1: Reaction of white phosphorus (P$_4$) with thionyl chloride (SOCl$_2$) produces phosphorus trichloride (PCl$_3$) and sulfur dioxide (SO$_2$): \[ P_4 + 8SOCl_2 \rightarrow 4PCl_3 + 4SO_2 + 2S_2Cl_2 \] 2. Step 2: Hydrolysis of PCl$_3$ produces phosphorous acid (H$_3$PO$_3$): \[ PCl_3 + 3H_2O \rightarrow H_3PO_3 + 3HCl \] Thus, [A] = PCl$_3$ and [B] = H$_3$PO$_3$, corresponding to option (3).