Question

Ethers like ROR can be cleaved by concentrated HI but not by HCl because:

• A. $I^{-}$ is a weaker nucleophile than $C{l}^{-}$
• B. $I^{-}$ is stronger nucleophile than $C{l}^{-}$
• C. $S_{N}1$ mechanism carried out in this reaction is rapidly in presence of HI.
• D. None of the above

Answer 1

The correct option is B $I^{-}$ is stronger nucleophile than $C{l}^{-}$

The cleavage of ether ($ROR$) by a halogen hydracid is eventually a $S_{N}2$ type displacement where halide $ion\left(X^{-}\right)$ acts as a nucleophile. Since, $I^{-}$ is a very strong nucleophile compared to $C{l}^{-}$, reaction easily occurs when $HI$ is used and not by $HCl$.

$R-O-R+HI-R-{\underset{H}{\underset{|}{O}}}^{\oplus }-R+I^{-}$