Ether

[moo]

The Chemistry of Functional Groups: The Chemistry of Ether Linkage, Interscience, London, 1967, p.694:

3. Inhibition of peroxides

No single method seems to be suitables for inhibiting peroxide formation in all types of ethers, although storage and handling under an inert atmosphere would be a generally useful precaution.

Some of the materials which have been used to stabilize ethers and inhibit formation of peroxide include the addition of 0.001% hydroquinone or diphenylamine^33,35, polyhydroxyphenols, aminophenols, and arylamines. 0.001 g of pyrogallol in 100 cc ether was reported to prevent peroxide formation over a period of two years³². Water will not prevent formation of peroxides in ethers, and iron, lead, and aluminium will not inhibit the peroxidation of diisopropyl ether³⁸ although iron does act as an inhibitor in diethyl ether. Dowex-1 has been reported effective for inhibiting peroxide formation in diethyl ether³⁹; 100 p.p.m. of 1-naphtol for diisopropyl ether ⁴⁰, hydroquinone for tetrahydrofuran ⁴¹, and stannous chloride or ferrous sulfate for dioxane⁴⁰ and substituted stilbenequinones have been proposed⁴² as stabilizers against oxidation of ethers and other compounds.

4. Removal of peroxides

Reagents which have been used for removing hydroperoxides from solvents are reported by Davies³² to include sodium sulfite, sodium hydrogen sulfite, stannous chloride, lithium aluminun hydride (caution: see notes in sections II.G and IV.B), zinc and acid, sodium and alcohol, copper-zinc couple, potassium permanganate, silver hydroxide, and lead dioxide. Decomposition of the peroxides with ferrous sulfate is a commonly used method--454 g (1 lb) of 30% ferrous sulfate solution in water is added to each 11.4 l (30 gal)⁴³. Caution is needed since the reaction may be vigorous if the solvent contains a high concentration of peroxide.

Reduction of alkylidene or dialkyl peroxides is more difficult but reduction by zinc in acetic acid or hydrochloric acid, sodium in alcohol (see note on case of ignition of hydrogen liberated from water), or the copper-zinc couple might be used for purifying solvents containing these peroxides³².

Addition of one part 23% sodium hydroxide to 10 parts of diethyl ether or tetrahydrofuran removed peroxides completely after agitation for 30 minutes; sodium hydroxide pellets reduced but did not remove the peroxide contents of tetrahydrofuran after two days²⁸. Addition of 30% N chloroform to tetrahydrofuran inhibited peroxide formation until the eighth day with only slight change during 15 succeeding days of tests²⁸. The peroxides were removed from the mixture by agitating it with 1% aqueous sodium borohydride for 15 minutes (with no attempt made to measure temperature rise or evolution of hydrogen).

A simple method for removing peroxides from high quality ether samples without need for a distillation apparatus or appreciable loss of ether consists of percolating the solvent throught a column of Dowex-1 ion-exchange resin³⁹. A column of alumina was used to remove peroxides and traces of water from diethyl ether, dibutyl ether, and dioxane⁴⁴ and also for removing peroxides from tetrahydrofuran and diisopropyl ether³².

Calcium hydride can be used for obtaining anhydrous and peroxide-free p-dioxane⁴⁵, by refluxing followed by distillation. The use of sodium and potassium borohydrides to reduce peroxide in tetrahydrofuran and diethylene glycol dimethyl ether (diglyme) and to inhibit them for some time against further peroxidation has been reported⁴⁶.

For removing peroxides from ethers the need and value has been expressed for an insoluble solid which can be separated by filtration or decantation. Cerous hydroxide (Ce(OH)₃) fulfills these requirements⁴⁷. Cerous hydroxide, prepared from a cerous salt solution by sodium hydroxide, changes from white to reddish brown within a minute or two after addition to an ether if peroxides are present; removal of peroxides can be completed within 15 minutes. The peroxyceric compound and unchanged cerous hydroxide can be removed by centrifugation (caution:: flammable vapors ignite if the sentrifuge is electric and not explosion-proof) and decantation. After treatment with cerous hydroxide each of twelve ethers which had previously contained peroxides gave negative potassium iodide tests. After the removal of peroxides, the ethers were tested for the prescence of cerium by the benzidine test, with negative results except for allyl ethyl ether and benzyl n-butyl ether. It was noted that di-t-butyl peroxide did not liberate iodine from acidified potassium iodide solution nor did it react with cerous hydroxide⁴⁷.


24. R. B. Moffett and B. D. Aspergren, "Tetrahydrofuran can cause fire when when used as a solvent for LiAlH₄", Chem. Eng. News., 32, 4328 (1954).
28. E. Fleck, Merck, Sharp & Dohme Company Memo, May 11, 1960.
32. A. G. Davies, "Explosion hazards of autoxidized solvents", J. Roy. Inst. Chem., 386 (1956).
33. G. Lindgren, "Autoxidation of diehtyl ether and its inhibition by diphenylamine", Acta. Chim. Scand., 94, 110 (1946).
35. A. G. Davies, Organic Peroxides, Butterworths, London, 1961.
38. P. R. Dugan, Ind. Eng. Chem., 56, 37 (1964).
39. R. N. Feinstein, "Simple method for removal or peroxides from diethyl ether", J. Org. Chem., 24, 1172 (1959).
40. Encyclopedia of Chemical Technology, Vol. 5, (Ed. R. E. Kirk and D. F. Othmer), Interscience Publishers, New York, 1950, pp. 871, 142.
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42. D. G. Jones,

Patent GB699079

(1953); Chem. Abstr., 49, 3262f (1955).
43. Chemical Safety Data Sheet--SD 29, Ethyl Ether, Manufacturing Chemists' Association, Washington, D.C., 1956.
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45. E. R. Birnbaum, personal communication, August 11, 1964.
46. Manual of Techniques, Metal Hydrides, Inc., Beverly, Massachusetts, 1958.
47. J. B. Ramsey and F. T. Aldridge, "Removal of peroxides from ethers with cerous hydroxide", J. Am. Chem. Soc., 77, 2561 (1955).



Organic Peroxides, Butterworths, London, 1961, p. 344:


Removal of Peroxides

The gradual formation of peroxides in many organic compounds, particularly solvents and the purified hydrocarbons derived from petroleum industry, made it inevitable that means would be devised whereby such compounds could be removed or decomposed so as to avoid explosions during subsequent processing.

The use of lead dioxide for decomposition and prevention of peroxides in ether¹⁰⁰ reflects the discovery by Criegee, Pilz and Flygare¹⁰¹ that hydroperoxides are converted to other compounds (generally ketones) on treatment with lead tetra-acetate or lead dioxide. Presumably the exploside cyclic peroxides present in autoxidised ether are unaffected by this reagent.

Solid potassium hydroxide¹⁰², calcium hydroxide precipitated from calcium chloride by sodium hydroxide¹⁰³ and a copper-zinc couple¹⁰⁴ have also been proposed as efficient means of removing peroxides from solvents. Some solvents can be freed from peroxides by passage through a column or alumina; this method has been found to be particularly applicable to dioxan and di-n-butyl ether, but is not so successful for diethyl ether¹⁰⁵.

Two methods have recently been reported for treating autoxidised ether. The first utilised an acid solution of ferrous sulphate for washing the ether, and it is claimed that peroxides are reduced to at least 2.5 parts per million by this means¹⁰⁶. In the second method the ether was treated with the hydroxyl form of the anion-exchange resing, Dowex 1; it was also noticed that if fresh ether was stored over this resin peroxide formation was largely prevented¹⁰⁷.

Methods of removal of peroxides from olefins by treating with alkali or sulphides¹⁰⁸, from various hydrocarbons by use of finely divided iron¹⁰⁹, and from cracked gasolines by hydrogenation¹¹⁰, have all been proposed.

It has been claimed that tetrahydrofuran can be stabilised against peroxide formation by the addition of cuprous chloride¹¹¹.


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I guess the above can be interpreted so that storing diethyl ether over NaOH will stabilize it.