Question

Which statement is correct for the conversion of $ROH$ to $RX$ by reagents $A(SOC{l}_2,PB{r}_3,PC{l}_3$ and $P{I}_3)$ compared to using $HX$?

• A. No rearrangement occurs with predictable stereochemistry by reagents (A)
• B. Reagents (A) are not useful for $3^{\circ }$ alcohols, while $HX$ reacts easily with $3^{\circ }$ alcohols involving rearrangement
• C. Reagents (A) must be used in anhydrous conditions because they react with water to form gases ($S{O}_2,HCl,HBr,$ and $HI$)
• D. All of the above are correct

Answer 1

The correct option is D All of the above are correct

Alcohols can be converted to alkyl halide by the reagents (A) without undergoing rearrangement. However, reaction with $HX$ proceeds through rearrangement having most stable carbocation intermediate.
Reagent (A) must be used in anhydrous condition because it will undergo hydrolysis and loose the required chemical activity.
Ex: $SOC{l}_2+H_{2}O\to S{O}_2+HCl$
$PC{l}_3+H_{2}O\to H_{3}P{O}_3+HCl$