On what basis does the R-O Cleavage takes place when R-O-R reacts with HI ?
 eg-: CH3-CH2-CH2-O-CH3 + HI ---> CH3-CH2-CH2-OH + CH3I ,
Why is the product not CH3-CHI-CH3 + CH4 ? 

Asked by Rohit Virinchi | 11th Mar, 2015, 02:41: PM

Expert Answer:

The clevage of ethers by halogen acids occurs by the following mechanism:
step 1: Ethers being Lewis bases, undergo protonation to form oxonium ions. In this compound the oxonium ion formed is given below.
Step 2: Iodide ion is a good nucleophile. Due to steric hindrance, it attacks the smaller alkyl group of the oxonium ion formed in step 1 and displaces the alcohol molecule by SN2 mechanism as shown below:
In the given molecule, methyl group is smaller alkyl group, hence methyl iodide is formed.

Answered by Prachi Sawant | 12th Mar, 2015, 12:22: PM