Acetyl. Peroxide

A mixture of 20 g. (0.196 mole) of acetic anhydride, 100 ml. of ether, and 10 g. (0.128 mole) of sodium peroxide is cooled to —15°, and 35 g. of finely crushed ice is added over a 10-minute period with vigorous agitation. The ice must be added very slowly at first. Agitation is continued for 10 minutes, and the ethereal layer is separated and dried over calcium chloride. The solution is allowed to stand at room temperature until the ether has evaporated. The residual crystalline solid is washed with a small amount of ether. The resulting product weighs 9 g. (59% yield based on peroxide) and melts at 26-27°. 

Acetyl peroxide decomposes explosively when heated rapidly above its melting point, and it must be handled with extreme caution at ordinary temperature. According to Kuhn, Chem. Eng. News., 26, 3197 (1948), acetyl peroxide prepared by this method should be used within 24 hours of its preparation, and the preparation itself should be completed without interruption. 

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A fixed-bed reactor for this hydrolysis that uses feed-forward control has been described (11) the reaction, which is first order ia both reactants, has also been studied kiaeticaHy (12—14). Hydrogen peroxide interacts with acetyl chloride to yield both peroxyacetic acid [79-21-0] and acetyl peroxide... 

Acetyl peroxides Hydrogen peroxide (< 35% water) Picric acid and Cu. Pb and Zn salts, (dry)... 

The thermal decomposition of diacyl peroxides has been the most frequently employed process for the generation of alkyl radicals. The rate and products of the unimolecular decomposition of acetyl peroxide have been the subject of many studies. Acetyl peroxide decomposes at a convenient rate at 70-80°C both in the solution and in the gas... 

The competitive method employed for determining relative rates of substitution in homolytic phenylation cannot be applied for methylation because of the high reactivity of the primary reaction products toward free methyl radicals. Szwarc and his co-workers, however, developed a technique for measuring the relative rates of addition of methyl radicals to aromatic and heteroaromatic systems. - In the decomposition of acetyl peroxide in isooctane the most important reaction is the formation of methane by the abstraction of hydrogen atoms from the solvent by methyl radicals. When an aromatic compound is added to this system it competes with the solvent for methyl radicals, Eqs, (28) and (29). Reaction (28) results in a decrease in the amount... 

The methoxy group of methyl acetate formed during the thermal decomposition of acetyl peroxide appears as an emission, whereas methyl chloride shows enhanced absorption. Consider the reaction sequence in equation (40). 

The kinetic form of the decomposition in various solvents indicates competing unimolecular homolysis of the peroxide link (a) and radical induced decomposition (b). Other diacyl peroxides behave similarly, except that, in the case of acetyl peroxide, induced dceomposition is much less important. More highly branched aliphatic or a-phenyl-substituted diacyl peroxides decompose more readily, partly because induced decomposition is more important again and partly because of the occurrence of decomposition involving cleavage of more than one bond (for a mechanistic discussion of these cases, see Walling et al., 1970). 

For benzoyl and acetyl peroxides, loss of carbon dioxide occurs in a stepwise process. Estimates of the rate constants for step c in Scheme 1 are 7 x 10 sec (benzene, 60°). The corresponding process for acetyl peroxide has k = 2x 10 sec (n-hexane, 60°), so that the lifetime of radical pairs containing acetoxy radicals is comparable to the time necessary for nuclear polarization to take place (Kaptein, 1971b Kaptein and den Hollander, 1972 Kaptein et al., 1972). Propionoxy radicals are claimed to decarboxylate 15-20 times faster than acetoxy radicals (Dombchik, 1969). 

The polarization of biphenyl, deserves special comment. If, as indicated in Scheme 2, its immediate precursor is a radical pair consisting of two phenyl radicals, then it should be formed without detectable net polarization since if Ag = 0. Analogous results have been reported in the decomposition of other peroxides for example, ethane formed from acetyl peroxide shows net emission. To account for this, it has been suggested (Kaptein, 1971b, 1972b Kaptein et al., 1972) that nuclear spm selection which occurs in the primary radical pair—in... 

Methyl formate Formic acid, methyl ester (8,9) (107-31-3) Acetyl peroxide (8) Peroxide, diacetyl (9) (110-22-5)... 

The same is true for peroxides and peroxy acids so performic and peracetic acids or acetyl peroxide are particularly dangerous, whereas perstearic acid (eighteen carbon atoms) is perfectly stable. 

A mixture of ketene and hydrogen peroxide gives rise to a violent detonation that was put down to acetyl peroxide. 

Barium peroxide had been used instead of potassium permanganate to purify acetic anhydride. Several operations had been carried out and the technicians had realised that this medium gives rise to mild deflagrations. During the last test a very violent detonation took place. It was thought that acetyl peroxide had formed. 

The peroxide was substituted for (unavailable) potassium permanganate in a process for purifying the crude anhydride in an open vessel. After several operations, when only minor explosions occurred, a violent explosion and fire occurred. Acetyl peroxide would be produced. 

Dining an attempt to prepare an anhydrous 25% solution of peroxyacetic acid in acetic acid by dehydrating a water-containing solution with acetic anhydride, a violent explosion occurred. Mistakes in the operational procedure allowed heated evaporation to begin before the anhydride had been hydrolysed. Acetyl peroxide could have been formed from the anhydride and peroxyacid, and the latter may have detonated and/or catalysed violent hydrolysis of the anhydride [1], A technique for preparing the anhydrous acid in dichloromethane without acetyl peroxide formation has been described [2],... 

Acetyl peroxide may readily be prepared and used in ethereal solution. It is essential to prevent separation of the crystalline peroxide even in traces, since, when dry, it is shock-sensitive and a high explosion risk [1], Crystalline material, separated and dried deliberately, detonated violently [2], The commercial material, supplied as a 30% solution in dimethyl phthalate, is free of the tendency to crystallise and is relatively safe. It is, however, a powerful oxidant [1]. Precautions necessary for the preparation and thermolysis of the peroxide have been detailed [3,4],... 

The back recombination of the pair of acetoxyl radicals with the formation of parent diacetyl peroxide was observed in special experiments on the decomposition of acetyl peroxide labelled by the lsO isotope on the carbonyl group [78,79]. The reaction of acetyl peroxide with NaOCH3 produces methyl acetate and all lsO isotopes are contained in the carbonyl... 

Thus the autoxidation of the aldehydes leads finally to acids. That a per-acid is first formed can be very easily shown in the case of acetaldehyde by the immediate liberation of iodine from potassium iodide solution which is caused hy this strong oxidising agent. In the case of benzaldehyde, which combines exceptionally rapidly with oxygen, it has been possible to trap the per-acid with acetic anhydride as benzoyl-acetyl peroxide (Nef) ... 

Mixing sodium percarbonate with acetic anhydride led to explosive shattering of the flask [1], undoubtedly caused by the formation of acetyl peroxide. The name sodium percarbonate has been used indiscriminately to describe 3 different compounds, all of which would react with acetic anhydride to give extremely explosive acetyl peroxide [2], These are sodium monoperoxycarbonate, NaOCO.OONa, [4452-58-8] sodium peroxydicarbonate, NaOCO.OOCO.ONa, [3313-92-6] and sodium carbonate sesqui hydrogen peroxidate, Na0C0.0Na.l,5H202, [15630-89-4],... 

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