It attacks the least substituted carbon of the oxonium
ion formed in step 1 and displaces an alcohol molecule by SN2
 mechanism Thus, in the cleavage of mixed ethers with two different alkyl groups, the alcohol
and alkyl iodide formed, depend on the nature of alkyl groups When primary or
secondary alkyl groups are present, it is the lower alkyl group that forms alkyl
iodide (SN2 reaction) When HI is in excess and the reaction is carried out at high temperature,
ethanol reacts with another molecule of HI and is converted to ethyl iodide