Question

Question:Like alcohols, ethers undergo α cleavage by breaking a carbon–carbon bond between an alkyl group and the carbon bonded to the ether oxygen atom; that is, the red C–C bond in $\mathbf{R}–{\mathbf{CH}}_2\mathbf{OR}\text{'}$is broken. With this in mind, propose structures for the fragments formed by α cleavage of${\left({\mathbf{CH}}_3\right)}_2{\mathbf{CHCH}}_2{\mathbf{OCH}}_2{\mathbf{CH}}_3$. Suggest a reason why an ether fragments by α cleavage.

Short answer

Answer

Resonance stabilization favors fragmentation.

Step-by-step solution

Step 1: α-cleavage of ethers

α-cleavage of ethers occurs between the C-C bond that is adjacent to the ether oxygen. The cleavage results in the formation of an alkyl radical and a resonance-stabilized carbocation containing the oxygen atom. The reaction is given below.

α-cleavage of ether

Step 2: α-cleavage of  (CH3)2CHCH2OCH2CH3

The α-cleavage of the given ether occurs in two ways, as shown below.

α-cleavage of the given ether

Ethers can form fragments viaα-cleavage because of the formation of the resonance-stabilized carbocations, which acts as the driving force for the cleavage to occur.

The resonance-stabilized structures of the two carbocations formed upon cleavage of the above ether are given below.

Resonance stabilization of the carbocations