Question

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

• A. No rearrangement occurs with predictable stereochemistry by reagents $\left(A\right)$
• B. Reasgents $\left(A\right)$ are not useful for $3^{\circ }$ alcohols, while $HX$ reacts easily with $3^{\circ }$ alcohols involving no rearrangement.
• C. Reagents $\left(A\right)$ must be used in anhydrous conditions because all react vigorously with $H_{2}O$ and they produce harmful gases $(S{O}_2,HCl,HBr,andHI)$
• D. All of the above

Answer 1

The correct option is D All of the above

All the three statements (A), (B) and (C) are correct. Hence, (D) is the correct option.

(A) No rearrangement occurs with predictable stereochemistry by reagents $\left(A\right)$. However if $HX$ is used, the rearrangement is possible.

(B) Reagents $\left(A\right)$ are not useful for tertiary alcohols, while $HX$ reacts easily with tertiary alcohols involving no rearrangement.

(C) Reagents $\left(A\right)$ must be used in anhydrous conditions because all react vigorously with $H_{2}O$ and they produce harmful gases ($S{O}_2$, $HCl$, $HBr$ and $HI$).

For example, phosphorous trichloride reacts with water to form orthophosphorous acid and $HCl$.

$PC{l}_3+3H_{2}O\to P(OH{)}_3+3HCl$