11.6: Autoxidation of Ethers to Peroxides and Hydroperoxides
Ethers represent a class of chemical compounds that become more dangerous with prolonged storage because they tend to form explosive peroxides when standing in the air. Autoxidation is the spontaneous oxidation of a compound in air. In the presence of oxygen, ethers slowly oxidize to form hydroperoxides and dialkyl peroxides.
If concentrated or heated, these peroxides may explode. Hence, ethers should be obtained in small quantities, kept in tightly sealed containers, and used promptly to prevent such explosions. Autoxidation of ethers proceeds by a free-radical chain reaction consisting of a series of steps—initiation, propagation, and termination in repetitive cycles. Each of these steps forms intermediate products called chain carriers that regenerate in each step. Such a reaction will continue as long as the chain carriers persist. Hydroperoxides and peroxides can be detected by shaking ether samples with an acidified aqueous 10% solution of potassium iodide, thereby liberating iodine which gives the yellow color to the solution.