Alcohol formation [ether cleavage]

Alcohol formation [ether cleavage] Definition:


When treated with acid, ether od tertiary, benzylic, or allilyc carbons can fragment to give a carbocation, which is then trapped by a nucleophile in an SN1 reaction.



Alcohol formation [ether cleavage] Explained:


Ethers are mostly unreactive in basic or mildly conditions which make them an ideal choice as a solvent. Ethers have a poor leaving group so they must first be converted to a good leaving group by reaction with strong acids. In these conditions, they can undergo substitution with both SN1  and SN2 mechanism. Which of these two mechanisms will occur depends on the alkyl group of the ether. If alkyl group is tertiary, benzylic, or allylic then substitution is more likely to proceed via an SN1 process. As an acid source, HBr and HI are used. HCl is less efficient, and HF does not cause acidic cleavage of ethers.

This mechanism consists of three steps:

STEP 1. Protonation of the O atom forms a good leaving group



STEP 2. Loss of the leaving group (alcohol) and formation of carbocation



STEP 3. Nucleophilic attack (iodide) and generates alkyl iodide