Question

For the cleavage of ethers by halogen acids, the order of reactivity of halogen acids is :

• A. $HI>HBr>HCl$
• B. $HBr>HI>HCl$
• C. $HCl>HBr>HI$
• D. ethers do not undergo cleavage

Answer 1

Answer: (A)

$HI>HBr>HCl$

For the cleavage of ethers by halogen acids, the order of reactivity of halogen acids is $HI>HBr>HCl$.

$HI$ is preferred to $HBr$ because it is a stronger acid than $HBr$ and thus gives a greater concentration of the oxonium ion $R{O}^{+}HR$. Moreover, $I^{-}$ ion is a better nucleophile in $S{N}^2$ reaction than $B{r}^{-}$ ion.