Solvents containing peroxides

Some common chemicals, such as i-PrOH, can form peroxides in explosive concentrations [7]. Peroxides can react, sometimes vigorously, with reagents such as alkyllithiums, amines, and other oxidizable compounds. Testing by dip strips containing peroxidase is a convenient means to monitor the peroxides present in chemicals. Guidelines for the use of such strips and purification of solvents containing peroxides have been published [7]. 

Tetrahydrofuran forms explosive mixtnres with air within the range 2.0-11.8% by volume in air. It is susceptible to form organic peroxides when exposed to air or light. Severe explosion can occur during distillation, purification, or use of impure tetrahydrofuran. Solvent containing peroxide can explode when dried with caustic soda or caustic potash, or when evaporated and may catch Are in contact with lithium aluminum hydride or other metal hydrides. Violent reactions can occur when combined with strong oxidizers. 

Basically, three reactions were evoked to support the occurrence of 5a-C-centered radicals 10 in tocopherol chemistry. The first one is the formation of 5a-substituted derivatives (8) in the reaction of a-tocopherol (1) with radicals and radical initiators. The most prominent example here is the reaction of 1 with dibenzoyl peroxide leading to 5a-a-tocopheryl benzoate (11) in fair yields,12 so that a typical radical recombination mechanism was postulated (Fig. 6.6). Similarly, low yields of 5a-alkoxy-a-tocopherols were obtained by oxidation of a-tocopherol with tert-butyl hydroperoxide or other peroxides in inert solvents containing various alcohols,23 24 although the involvement of 5 a-C-centered radicals in the formation mechanism was not evoked for explanation in these cases. 

The biomimetic protocol was invented by Julia and Colonna, and involves the use of polyamino acids (such as poly-(L)-leucine) as the catalysts for peroxide oxidation of chalcones, styryl alkyl ketones and conjugated alkenones. The substrate range is broad, especially when using immobilized catalysts and an organic solvent containing the substrate, urea-hydrogen peroxide and an organic base (Scheme 22)[101]. 

Certain specific problems arise with the use of alkylamine-substi-tuted stationary phases. Since amines are readily oxidized, degassing the mobile phase and avoiding solvents that may contain peroxides, e.g., diethyl ether and tetrahydrofuran, are recommended. Samples or impurities in the mobile phase containing ketone or aldehyde groups may... 

One problem associated with using solid adsorbents to dry solvents is disposal of the used adsorbent, especially if large quantities of solvent are dried. Usually the adsorbent can be reactivated by careful heating in a stream of inert gas or under vacuum. (If the adsorbent was used to dry olefins or other peroxide-containing solvents, any peroxides must first be destroyed see Section 4.I.D.) Reactivating large quantities of adsorbent, however, can be just as difficult as proper disposal. 

List B, giving examples of liquids where a degree of concentration is necessary before hazardous levels of peroxides will develop, includes several common solvents containing one ether function (diethyl ether, ethyl vinyl ether, tetrahydrofuran), or two ether functions (p-dioxane, 1,1 -diethoxyethane, the dimethyl ethers of ethylene glycol or diethylene glycol ), the secondary alcohols 2-propanol and 2-butanol, as well as the susceptible hydrocarbons propyne, butadiyne, dicyclopentadiene, cyclohexene and tetra- and deca-hydronaphthalenes. Checking stocks at 12 monthly intervals, with peroxidic samples being discarded or repurified, is recommended here [1],... 

It comes as a liquid that typically contains low molar-mass, unsaturated polyester and styrene. The unsaturated polyester contains carbon-carbon double bonds. The polymerization is catalyzed with a hardener, an organic peroxide dissolved in an organic solvent. The peroxide forms free radicals that initiate polymerization of the styrene and crosslinking of the polyester. 

Distillation of solvents may be extremely dangerous because many nonaqueous solvents are volatile and flammable. Hence, the distillation systems have to be explosion proof and equipped with a safety valve which can liberate pressure which develops in the system. It should be noted that ether solvents may contain peroxides that can cause an explosion upon heating. In fact, any ether solvent that is exposed to air is suspected of containing dangerous peroxides. 

The rearrangement products derived from aromatic and non-aromatic heterocyclic amines crystallize readily from the lower alcohols. Unlike those of many of the A-substituted glycosylamines, the crystals are not solvated. On the other hand, the ketose derivatives of aralkyl- and alkyl-amines, such as 2-phenylethylamine, ethanolamine, diethanolamine, glycine ethyl ester, and phenylalanine (see Table II), are hydrated or alcoholated, or both, and are difficult to isolate in pure crystalline form. The crystals which have been isolated were hygroscopic. Alcohols, aqueous alcohols, and water are the most commonly used solvents for crystallization. Acetone, ether, or benzene have been added to the alcoholic media in order to increase the yield of crystalline compound. The use of solvents that contain peroxides promotes decomposition of the crystals during storage. ... 

A further example for the ozonization of an olefin in the presence of a solvent containing active hydrogen is the ozonolysis of 2-butene in acetic acid as solvent. The hydroperoxy ester was isolated as a pure and rather stable liquid. It is different from a crystalline autoxidation product of acetaldehyde (the peroxide of Losch ) which... 

Some organic solvents and oils have also been reported to contain peroxides.21 The level of peroxides in susceptible solvents can increase with time, depending on the storage conditions. 

Mobile, flammable liquid. Pungent, sweetish odor, d 0 0.8814, mp -49.2 . bp 885, n 1.4211. Dipole moment 1,87. Flash pt —4,0°F. Azeotrope with water, bp 71, contains 8.5% H,0. Sol in water [relative solubilities Bennett, Philip, J- Chem. Soc. 1928, (1939)]. Miscible with alcohol, ether, many other Organic solvents. Forms peroxides on exposure to air. All technical tetrahydropyran is stabilized against peroxide formation. 

The following solvents generally contain peroxides light petroleum, petrol (U.S. gas), decalin, aromatic hydrocarbons containing side chains (xylene, cumene), tetralin, all ethers. 

Diethyl ether, diisopropyl ether, tetrahydrofuran, and dioxan, as well as the hydrocarbons decalin and tetralin and even petroleum fractions and xylene, usually contain peroxides. Owing to their involatility, peroxides become enriched in distillation residues and have often given rise to very severe explosions.13 To avoid accidents when working with these solvents it is essential to test for the presence of peroxides and, if they are present, to take steps to remove them. Then, to suppress formation of further peroxides in these solvents, they must be stored in dark flasks and access of atmospheric oxygen must be very rigidly excluded. 

An alkoxylation at the C-7 position of compound 176 (to yield 177) occurred using A -bromosuccinimide or A -chlorosuccinimide in an alcohol solvent containing a catalytic amount of f r7-butyl peroxide. The formation of 177 does not occur through a conventional mechanism neither direct addition of alcohol to C-7 or substitution of a C-7 halo compound is operative, but the reaction is mediated by the presence of free radicals (Equation 24) <2002EJ02109>. 

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