Question

Following is an equation for the reaction of diisopropyl ether and oxygen to form a hydroperoxide. COC(C)(C)OC(C)C Diisopropyl ether A hydroperoxide Formation of an ether hydroperoxide is a radical chain reaction. (a) Write a pair of chain propagation steps that accounts for the formation of this ether hydroperoxide. Assume that initiation is by a radical, \(R\). (b) Account for the fact that hydroperoxidation of ethers is regioselective; that is, reaction occurs preferentially at a carbon adjacent to the ether oxygen.

Short answer

Answer: Hydroperoxidation of ethers is regioselective because the reaction occurs preferentially at a carbon adjacent to the ether oxygen. This is due to the stabilization of the alkyl radical formed during the reaction by the oxygen's lone pair electrons, leading to preferential formation of the hydroperoxide product at this position.

Step-by-step solution

Identify the structure of diisopropyl ether

The given SMILES notation for diisopropyl ether is COC(C)(C)OC(C)C. The structure of diisopropyl ether is as follows: $$ \text{CH}_3 \text{CH}( \text{CH}_3) \text{O} \text{CH}( \text{CH}_3) \text{CH}_3 $$ #step_2#

Write the chain propagation steps for the formation of ether hydroperoxide

We are assuming that the initiation is by a radical \(R\). The first step will involve abstraction of a hydrogen atom from diisopropyl ether by the \(R\) radical to produce an alkyl radical: $$ \text{CH}_3 \text{CH}( \text{CH}_3) \text{O} \text{CH}( \text{CH}_3) \text{CH}_3 + \text{R}\cdot \rightarrow \text{CH}_3 \text{C}\left( \text{CH}_3 \right) \text{O} \text{CH}( \text{CH}_3) \cdot\text{CH}_3 + \text{R}\text{H} $$ The second step will involve the reaction of the formed alkyl radical with oxygen to generate an ether hydroperoxide: $$ \text{CH}_3 \text{C}\left( \text{CH}_3 \right) \text{O} \text{CH}( \text{CH}_3) \cdot\text{CH}_3 + \text{O}_2 \rightarrow \text{CH}_3 \text{C}\left( \text{CH}_3 \right) \text{O} \text{CH}( \text{CH}_3) \text{CH}_3\text{OO}\cdot $$ #step_3#

Explain the regioselectivity of hydroperoxidation of ethers

Hydroperoxidation of ethers is regioselective because the reaction occurs preferentially at a carbon adjacent to the ether oxygen. This is because the ether oxygen present in the molecule has lone pair electrons that can stabilize the alkyl radicals formed during the reaction. The carbon atom adjacent to the ether oxygen is more likely to form a stable alkyl radical due to resonance stabilization provided by the oxygen's lone pair electrons. This increased stability of the alkyl radical at the carbon adjacent to the ether oxygen leads to preferential formation of the hydroperoxide product at this position.