Question

Which of the following ethers cannot initiate radical peroxide formation?

Answer 1

Di(tert-butyl) ether (`("H"_3"C")_3-"C"-"O"-"C"-("CH"_3)_3`). It has no `alpha`-proton.

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The first step in radical peroxide formation is the abstraction of an `alpha`-proton by a radical initiator. If that is not possible, then this mechanism cannot start.

REACTION MECHANISM

The general mechanism goes as follows (suppose our radical initiator is `"Cl"cdot"`, which you can generate by exposing `"Cl"_2` to UV light).

1. A radical initiator abstracts an `alpha`-proton from the starting ether.
2. Triplet (`""^3 Sigma`) oxygen (`cdot"O"-"O"cdot`) then reacts with the newly-formed radical to form a peroxide radical intermediate.
3. The intermediate can react with the original ether to generate a peroxide product and regenerate the radical that reacts with `""^3 Sigma` `"O"_2`.

This is an explosive reaction, so generally, one should dispose of any purified ethers exposed to air within 24 hours.

WHICH ONE CAN'T REACT IN THIS WAY?

When we examine each reactant's structure, only di(tert-butyl) ether doesn't have an `alpha`-proton.

So, di(tert-butyl) ether wouldn't be able to be turned into the reactive radical form that generates the peroxide.