Ethers peroxides from

Tetrahydrofuran (cyclic ether) Peroxide from diethyl ether... 

Low molecular weight ether hydroperoxides are similarly dangerous and therefore ethers should be tested for peroxides and any peroxidic products removed from them before ethers are distilled or evaporated to dryness. Many ethers autoxidize so readily that peroxidic compounds form at dangerous levels when stored in containers that are not airtight (133). Used ether containers should be handled cautiously and if they are found to contain hazardous soHd ether peroxides, bomb-squad assisted disposal may be required (134). ZeoHtes have been used for removal of peroxide impurities from ethers (135). 

A simple test for ether peroxides is to add lOmL of the ether to a stoppered cylinder containing ImL of freshly prepared 10% solution of potassium iodide containing a drop of starch indicator. No colour should develop during one minute if free from peroxides. Alternatively, a 1% solution of ferrous ammonium sulfate, O.IM in sulfuric acid and O.OIM in potassium thiocyanate should not increase appreciably in red colour when shaken with two volumes of the ether. 

Ethers are relatively stable and unreactivc in many respects, but some ethers react slowly with the oxygen in air to give peroxides, compounds that contain an 0-0 bond. The peroxides from low-molecular-weight ethers such as diisopropyl ether and tetrahydrofuran arc explosive and extremely dangerous, even in tiny amounts. Ethers are very useful as solvents in the laboratory, but they must always be used cautiously and should not be stored for long periods of time. 

Anhydrous Ethyl Ether. This is for those formulas calling for dry, pure, or anhydrous ether. The ether product from above is dried over thin slices of metallic sodium (metallic sodium wire works well also) for 24 hours. Then the ether is distilled on a water bath, over fresh (fresh means a different batch than what you used to dry with) metallic sodium. Note Ether develops explosive peroxides upon sitting for any length of time, even if just purchased from a supply house. Therefore, before handling ether, which has been stored, shake with ferrous sulphate or with lead peroxide. To keep peroxides from forming in fresh ether add several sections of copper or iron wire to the dark container and store in a cool place. 

The very sensitive ether peroxide test strips (Merckoquant, Art. No. 10011), available from E. Merck, Darmstadt, are used. If the test is still positive at this point, an additional 0.2 ml. of N-methyl morpholine is added. Stirring and heating at 75° are continued for another 5 hours. Remaining peroxide renders the work-up and drying of the product potentially hazardous. N-Methylmorpholine N-oxide (1) and hydrogen peroxide form a strong 1 1 complex. In the reaction with osmium tetroxide, this complex produces conditions similar to those of the Milas reaction,7 and some ketol formation may result. 

The filtrate obtained from this reaction mixture is reduced to a volume of 15.0mL in a rotating evaporator and purified by means of thin layer chromatography (TLC) preparative plates of 1-mm thickness (Kieselgel P. F. Merck) eluant diethyl ether (5% vol) in light petroleum ether. The dark brown band of the complex is eluted with dry diethyl ether (peroxide-free). 

Diphenylbenzo[c]furan is reportedly attacked by oxygen without catalysts in the dark, even in the solid state. When a solution of 138 in benzene (or toluene) is treated with oxygen, on precipitation with ether a white powder with mp 140°C is obtained in 82% yield on heating to 150— 170°C explosion occurs/ lodometric titration in tetrahydrofuran showed a content of 94% peroxide from this solution 37% o-dibenzoylbenzene (140) has been obtained. The molecular weight was determined to be 2830 (cryoscopic in benzene) and th6 structure formulated as 241 ( = 8-10). 

AMC Safety Manual", AMCR 385-224, US Army Materiel Command, Washington,DC (June 1964) 119)H.,W.Fawcett W-S.Wood, "Safety and Accident Prevention in Chemical Operations , Interscience, NY (1965), 6l7pp 120)The Indicator (May 1965), p 34 (Hazards from ether peroxides)... 

Removal of peroxides.1 Self-indicating activated 4 A molecular sieve (J. T. Baker, Merck) effectively removes peroxides from various ethers. The effectiveness is not a result of adsorption but of interaction with the impregnated indicator. 

Stannous chloride has been used to remove peroxides from dioxane and ether, Fisher and Baxter, Colo. School Mines Mag., 30, 447 (1940)[C. A., 84, 8111 (1940)1. 

Though many open-chain diacyl peroxides have been described, very few cyclic compounds of this type are known. Monomeric cyclic phthaloyl peroxide (84) is prepared by treatment of phthaloyl chloride in chloroform with aqueous sodium peroxide solution in the presence of phosphate buffer, or by reaction of phthaloyl chloride with ethereal hydrogen peroxide in the presence of sodium carbonate.70-72 Russell71 has also obtained cyclic diacyl peroxides from the dichlorides of the C10, C12, and C14 dicarboxylic acids. Only polymeric diacyl peroxides were obtained from lower dicarboxylic acids. 

Detection and removal of peroxides from solvents Organic Solvents Physical Properties and Methods of Purification, 4th ed., ed. J. A. Riddick et al. (Chichester Wiley, 1986). Deperoxidation of ethers with molecular sieves Burfield, D. R., J. Org. Chem., Al, 3821-3824, 1982. 

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