Question

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

Short answer

**Question**: Describe the radical chain reaction that leads to the formation of ether hydroperoxide from diisopropyl ether, and explain the regioselectivity of the hydroperoxidation of ethers. **Answer**: The radical chain reaction comprises two propagation steps: 1) A radical R attacks the diisopropyl ether, producing a diisopropyl ether radical and a new R radical. 2) The diisopropyl ether radical then reacts with molecular oxygen to form the ether hydroperoxide. The hydroperoxidation of ethers is regioselective because it occurs preferentially at the carbon adjacent to the ether oxygen. This is due to the higher electronegativity of oxygen in the ether, which increases the electron density on the neighboring carbon atom, making it more susceptible to radical attack and subsequent hydroperoxidation.

Step-by-step solution

Identify the structure of diisopropyl ether and hydroperoxide

The given SMILES notation for diisopropyl ether is COC(C)C(C)OC(C)(C)C. The structure is shown below: ``` O / \ C C | | C C / \ / \ H H H H ``` A hydroperoxide contains an oxygen-oxygen single bond with one of the oxygens bonded to a carbon atom. Its general formula is \(\mathrm{ROOH}\), where \(\mathrm{R}\) is an alkyl or aryl group.

Write the chain propagation steps

We are assuming that initiation is by a radical \(\mathrm{R}\). The chain propagation steps are as follows: 1. \(\mathrm{R \cdot + Diisopropyl Ether \rightarrow Diisopropyl Ether \cdot + R}\) The radical \(\mathrm{R}\) reacts with diisopropyl ether to form a diisopropyl ether radical and a new radical \(\mathrm{R}\). 2. \(\mathrm{Diisopropyl Ether \cdot + O_2 \rightarrow Ether Hydroperoxide}\) The diisopropyl ether radical reacts with molecular oxygen to form the ether hydroperoxide.

Explain the regioselectivity

The hydroperoxidation of ethers is regioselective because it occurs preferentially at a carbon adjacent to the ether oxygen. This preferential reactivity is due to the higher electron density of the carbon atom alpha to the oxygen in the ether. The oxygen in the ether has higher electronegativity, which increases the electron density on the neighboring carbon atom. As a result, this carbon is more likely to be attacked by the radical species, leading to hydroperoxidation. Consequently, the ether hydroperoxide forms predominantly at the carbon adjacent to the ether oxygen.