Ethers peroxidation

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. 

List C deals with butadiene and unsaturated compounds, but does not include any ethers. Peroxides that are formed with the compounds in this list catalyse their polymerisation. This is the dangerous reaction. 

Ether peroxidation was responsible for the detonation that occurred when dibenzyl ether was treated by the etherate of dichloroaluminium hydride. Note that in this case as well as for diallyl ether there will be easy peroxidation since both sites are of allyl and benzyl nature respectively. 

The detonation was put down to the presence of crotonaldehyde peroxide or ether peroxide. 

When air was admitted after vacuum evaporation of a (peroxidic) ether solution of the dinitro compound (5 g), a violent explosion occurred. Exploding ether peroxide may have initiated the dinitro compound. 

See ethers, peroxides in solvents See other peroxidisable compounds... 

They often detonate without warning when ether solutions are distilled to near dryness => test for and decompose any ether peroxides before a distillation is carried out. 

Note Acrylamide may contain the following impurities acetamide, acrylic acid, acrylonitrile, copper, formaldehyde, hydroquinone, methylacrylamide, hydroquinone monomethyl ether, peroxide, propanamide, and sulfate. When acrylamide is produced using a copper catalyt, copper salts may be added to aqueous solutions at concentrations >2 ppm (NICNAS, 2002). Commercial solutions 30-50%) are usually inhibited with copper salts to prevent polymerization. In addition, solutions containing oxygen will prevent polymerization. 

Polymeric Ethylidene Peroxide (Ether Peroxide) Extremely explosive, even below 100°C Eg, A. Rieche R. Meister, AngewChem 49, 101 (1936)... 

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). 

This experiment was performed on XAD-4 quaternary resin in the OH- form, and desorption was by ethyl ether only (i.e., HC1 saturated ether not used). Calcium hypochlorite [Ca(OCl)2] was used to provide the required 2-ppm chlorine concentration. Millipore Super-Q water was salted according to the general procedure and passed over a 10-mL bed volume of resin (approximate dry weight = 6 g at 150 bed volumes/h. The resins were blown with nitrogen (3 lb/in2) for 10 s to remove residual water and eluted with 3 X 50-mL portions of ethyl ether. Peroxide formation was suppressed by the addition of 2% (v/v) ethanol. 

Ethyl ether, peroxide free Methanol containing 1% acetic acid Silica gel thin-layer plates (2.5 X 10 cm)... 

Balaban, A. T., L. B. Kier, and L. H. Hall, Correlations Between Chemical Structure and Normal Boiling Points of Acyclic Ethers, Peroxides, Acetals, and Their Sulfur Analogues. J. Chem. Inf. Cornput. Sci., 1992 32, 237-244. 

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)... 

See ETHERS, PEROXIDES IN SOLVENTS See other PEROXIDISABLE COMPOUNDS... 

Acyclic ethers, peroxides, acetyls, and their sulfur analogues. 

Balaban, A.T., L.B. Kier, and N. Joshi. 1992b. Correlations between chemical structure and normal boiling points of acyclic ethers, peroxides, acetals, and their sulfur analogues. J. Chem. Inf. Comput. Sci. 32 237—44. 

Isopropyl ether Peroxides 1-10 ppm (mass/mass) BHT (1.5-3.5% ethanol) + (0.2-0.5% water) + (5-10 ppm (mass/mass) BHT) 0.01% (mass/mass) hydroquinone... 

An ether consists of two hydrocarbon moieties linked by an oxygen atom, as shown in Figure 14.7. Although diethyl ether is highly flammable, ethers are generally not very reactive. This property enables their uses in applications where an unreactive organic solvent is required. Some ethers form explosive peroxides when exposed to air, as shown by the example of diethyl ether peroxide in Figure 14.7. 

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

Step 4). The slightly alkaline aqueous solution is extracted five times with successive (800-1200 mL) portions of ether (peroxide-free). This combined ether extract is then distilled and the active residue treated first with 80 mL butyl alcohol and then with 1500 mL of petroleum ether as in Step 3. 

The chemistry of primary ozonides is more varied if they are less highly alkylated than the primary ozonide of Figure 15.47. This is particularly true if the primary ozonide is unsym-metrical, like the one shown in Figure 15.48. This is because its decay may involve two different 1,3-dipolar cycloreversions. Both of them result in one carbonyl oxide and one carbonyl compound. If the reaction is carried out in methanol, the two carbonyl oxides can react with the solvent (as in Figure 15.47) whereby each of them affords a hydroperoxide (an ether peroxide analog). 

Fig. 17.32. Oxidative cleavage of an asymmetric ketone with complementary regiose-lectivities. Lactone A is obtained by Baeyer-Villiger oxidation of menthone [2-methyl-5-(l- methylethyl)cyclo-hexanone]. Alternatively, one may first convert menthone into the silylenol ether B and cleave its C=C double bond with ozone to obtain a silyl ester containing an a-methoxyhydroperoxide group as a second functional group (which resembles the unstable structural element of the so-called ether peroxides cf. Figure 1.38). The latter is reduced with NaBH4tothe hydroxylated silyl ester C. The hydroxycarboxylic acid is obtained by acid-catalyzed hydrolysis. It cyclizes spontaneously to give lactone D.

---