what happens if a ether with a 2° alkyl group and a 1° alkyl group is cleaved with a halogen acid?
To this question I have drawn a scheme below. The given ether is $\ce{2^0}$ group to the left and methyl to right. Acid cleavage with a halogenic acid involves an initial protonation of ether. In an $\ce{S_N^2}$ reaction of this ether, nucleophile $\ce{I^-}$ attacks via path 1 and path2.
- In path 1, $\ce{I^-}$ approach is sterically hindered by phenyl and Methyl groups. This leads to a high energy transition state.
- In path 2, $\ce{I^-}$ approach is from right of protonated ether where steric hindrance is comparatively less( only $\ce{H}$). A more stable transition state favors $\ce{S_N^2}$ reaction .
