Radical peroxide, explosive, formation

Most ethers are potentially ha2ardous chemicals because, in the presence of atmospheric oxygen, a radical-chain process can occur, resulting in the formation of peroxides that are unstable, explosion-prone compounds (7). The reaction maybe generalized in terms of the following steps involving initiation, propagation, and termination. 

Peroxides. See also Inorganic peroxides Organic peroxides acid hydrolysis of, 23 459 diacyl, 24 282-284 explosive, 20 569-573 formation of, 20 577 as free-radical initiators, 24 279-293 organomercury-containing, 23 445 potassium salts of, 18 478 silylation and, 22 703 stereoisomers of, 28 459 as vulcanizing agents, 22 795 ... 

The preparation, properties and uses of ozonides have been reviewed comprehensively [1]. Many pure ozonides (trioxolanes) are generally stable to storage some may be distilled under reduced pressure. The presence of other peroxidic impurities is thought to cause the violently explosive decomposition often observed in this group [2], Use of ozone is not essential for their formation, as they are also produced by dehydration of c cF-dihydroxy peroxides [3], A very few isomeric linear trioxides (ROOOR) are known, they are also explosively unstable. Inorganic ozonides, salts of the radical C>3 anion, are also hazardous. 

Following fires in which endotracheal tubes became ignited by surgical lasers or electrocautery in atmospheres enriched by oxygen and/or nitrous oxide, the flammability of PVC, silicone rubber and red rubber tubes in enriched atmospheres was studied [1], Ozonised oxygen was reacted with hydrogen at low pressure to generate hydroxyl radicals. Pressure in the apparatus was maintained by a vacuum pump protected from ozone by a tube of heated silver foil. On two occasions there was an explosion in the plastic vent pipe from the vacuum pump. The vent gas should have been outside explosive limits and the exact cause is not clear the editor suspects peroxide formation. 

A peroxide is a compound with an O—O bond. Because an O—O bond is easily cleaved homolytically, a peroxide forms radicals that then can create new radicals—it is a radical initiator. Thus, the peroxide product of the preceding radical chain reaction can initiate another radical chain reaction— an explosive situation. To prevent the formation of explosive peroxides, ethers contain a stabilizer that traps the chain-initiating radical. Once an ether is purified (in which case it no longer contains the stabilizer), it has to be discarded within 24 hours. 

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