Patented Apr. 13, 1948 2,439.399 UNITED STATES PATENT of FICE PROCESS FOR THE PREPARATION OF - ACETY PEROXDE Edward S. Shanley, Kenmore, and Harlow G. Hyatt, Buffalo, N. Y., assignors to Buffalo Electro-Chemical Company, Inc., Tonawanda, N.Y. No Drawing. Application May 12, 1944, Serial No. 535,392 5 Claims, (C. 260-610) The present invention relates to a reagent con What less hazardous than crystalline acetyl per taining diacetyl peroxide and to a method of pre oxide. The experience of investigators dealing paring the same. with the ethereal solutions is that they are haz Diacetyl peroxide is the first member of a series ardous materials to work with, entirely aside of Organic peroxides. It has been known for from the fire hazard always associated with such many years and its properties have been studied solutions, by reason of their tendency to spon and recorded. Diacetyl peroxide possesses many taneous explosion. A possible explanation for characteristics which make it eminently suitable this behavior resides in the fact that explosive for use as an organic oxidant of high activity, as peroxides may be produced from ethyl ether even an alkylation reagent, as a polymerization cata i0 in contact with oxygen of the air. This tendency lyst, as well as other uses of lesser importance. undoubtedly exists to a much greater extent Although many organic peroxides possess the under the strong peroxidizing conditions existing properties enumerated, diacetyl peroxide is of during the preparation of the acetyl peroxide and particular interest as it possesses a relatively by reason of its presence in solution in ethyl large amount of available oxygen and may be 15 ether. Furthermore, during partial evaporation prepared from Iow-cost raw materials. Con of this solvent, ether peroxides may deposit on mercial utilization of these advantageous prop the container walls and these, by their spontane erties of diacetyl peroxide have not heretofore ous detonation, may initiate the explosion of the been possible by reason of the fact that diacetyl whole peroxide content of the system. peroxide itself is a relatively unstable material 20 Subsequent attempts have been made to pre as it is extremely sensitive to shock, decomposing pare diacetyl peroxide in mutual solvents in under shock conditions with extreme violence. which the fire hazard and the formation of per In fact, diacetyl peroxide in the crystalline state oxides with the solvent are relatively less. How is characterized as a member of a group of ma ever, these experiments produce diacetyl peroxide terials having extremely high shock sensitivity 25 in only a very small yield. In fact, many of these much greater than that possessed by mercury attempts have been unsuccessful as the desired fulminate. - peroxide has been obtained in the solvent layer As a consequence of these characteristics and either not at all or at yields pf only a few per behavior, substantially all investigations dealing cent, the presumption being that these organic with the preparation and properties of diacetyl 30 mediums were non-solvents for all of the react peroxide have been carried out in ethyl ether ants, notably hydrogen peroxide, or did not pro solution. Thus every operative prescription for vide a suitable reaction medium for inducing the preparation of acetyl peroxide listed in Beil peroxidation of the acetic anhydride or acetic stein specifies the use of ethyl ether as a medium acid. See Feiser and Oxford, for example, J. A. in which the preparation should be made. Sev 35 C. S. 64, 2060 (1942). eral procedural variations from that of Beilstein It is an object of the present invention to pro are to be found in the literature, all of which vide a method for preparing acetyl peroxide by involve the reaction of acetic anhydride and hy the employment of relatively non-inflammable drogen peroxide, or a percompound which lib organic solvents as the reaction medium. erates hydrogen peroxide upon treatment with 40. It is also an object of the invention to prepare : acetic acid, but all are performed in the presence diacetyl peroxide in the presence of an organic of ethyl ether. medium in which all of the reactants are not This choice of ethyl ether as a reaction medium soluble, but in which diacetyl peroxide is soluble. arises from the fact that it is a mutual Solvent It is also an object of the invention to provide for aqueous hydrogen peroxide, acetic anhydride 45 a method wherein diacetyl peroxide may be pro and the resultant end product, diacetyl peroxide. duced with excellent yield in the presence of a In fact, ethyl ether is an excellent medium, in non-mutual solvent which is non-inflammable sofar as this reaction itself is concerned, in which and which is not subject to peroxidation. to prepare diacetyl peroxide. However, the re It is also an object of the invention to provide sudting ethereal solution of acetyl peroxide can 50 a method for the production of diacetyl peroxide be handled and used only with the greatest pre which obviates all of the disadvantages of the cautions by reasons of the inflammability of this prior art methods of procedure, medium and the presence of a material pOSSess In accordance with the procedures of the pres ing a relatively high content of readily available ent invention, diacetyl peroxide may be prepared oxygen. However, the ethereal solution is some 55 in organic solvents of the ester type with excel

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2,489,899 3 4. lent yields even though the organic solvent em 11 g. barium dioxide suspended in 15 ml, Water. ployed be a non-mutual solvent for the reactants This mixture was agitated vigorously for about employed in producing diacetyl peroxide. To 15 minutes, with cooling. The organic layer was this end, water insoluble esters are chosen as the separated and dried. Yield 47 g. Active oxygen reaction medium in which diacetyl peroxide is S content 2.4%. This corresponds to 8.3.g. acetyl soluble and, therefore, the spent aqueous by peroxide which is 72% of the theoretical. products can be decanted from the resultant per In all the instances above, the ester was not oxide solution or layer. Thus typical solvents for miscible with water but was a solvent for acetyl this purpose are those water insoluble esters of peroxide. Esters generally, if water insoluble, the formula RCOOR, where R and R are nono 0 may be employed as the non-mutual solvent with or polyvalent organic radicals. By reacting hy production of a reagent that can be stored, drogen peroxide, or a percompound yielding hya transported and used in alkylation, polymeriza drogen peroxide with acetic acid, with acetic an tion and other reactions where acetyl peroxide hydride or acetic acid, acetyl peroxide is formed itself finds utility. The ester solutions are not in good yield and is found in the non-aqueous 5 readily inflammable and not subject to shock ester layer. Solutions of diacetyl peroxide in detonation as is the crystalline acetyl peroxide such esters may be formed in relatively high con and solutions thereof in ether. . centrations, with good yields, and the solutions The reaction may take place With any per may be used, handled and transported with per compound, i. e. a material yielding hydrogen fect safety, as they are free from the danger of 20 peroxide such as the alkali netal peroxides, spontaneous or induced explosion. These solu alkaline earth metal peroxides, other metal per tions are suitable for use directly as polymeriza Oxides, the perborates, percarbonates and the tion of vinyl compounds, for the bleaching of like, Generally alkaline hydrogen peroxide or oils, for carrying out organic syntheses involving the peroxides of alkali and alkaline earth metals diacetyl peroxide, and for many other purposes. 25 will be found most suitable. In the claims, these The following examples are intended to illus substances are comprehended within the term trate the practice of the present invention but inorganic peroxy compound. are not to be deemed as limitative thereof: What is claimed is: Eacample I 1. The method of making acetyl peroxide 30 which comprises reacting acetic anhydride and 102 g. acetic anhydride was dissolved in 320 g. hydrogen peroxide in the presence of an ester dimethyl phthalate and the mixture was cooled which is a non-mutual Solvent. to -5° C. To this cold mixture was added 41 g. 2. The method of making acetyl peroxide Sodium peroxide and then, With agitation, 100 g. which comprises reacting acetic anhydride and ice. After agitating vigorously for about 15 35 hydrogen peroxide in the presence of an ester of minutes, the aqueous layer was separated from phthalic acid. the dinnethylphthalate. The phthalate solution 3. The method of making acetyl peroxide was dried over calcium chloride and filtered, yield which comprises reacting acetic anhydride and 404 g. containing 2.8% active oxygen, by iodine hydrogen peroxide in the presence of dioctyl titration. Calculated as acetyl peroxide, this cor 40 phthalate. . responds to 84 g. or 70% of the theoretical yield. 4. The method of making acetyl peroxide That this active oxygen was not due to the which comprises, reacting acetic anhydride and presence of peracetic acid was indicated by the hydrogen peroxide in the presence of dimethyl slow reaction with KI. A portion of the organic phthalate, .. layer was shaken with an excess of water. No 5. The method of making acetyl peroxide hydrogen peroxide could be found in this water which comprises reacting acetic anhydride and (titanium sulfate test), which indicated that the hydrogen peroxide in the presence of methyl oxygen in the organic layer was not present as methacrylate. hydrogen peroxide. In consequence of these tests EDWARD S. SHANLEY. and observations on the properties of the solu HARLOW. G. HYAT. tion, it is established that the active oxygen coin tent is actually due to dissolved acetyl peroxide. REFERENCES CITED Eacample II The following references are of record in the 40 ml. methyl methacrylate was placed in a file of this patent: 55 flask and cooled to -5° C. To this was added UNITED STATES PATENTS 10.0 g. acetic anhydride and then 50 g. sodium hydroxide pellets. 6.0 ml. of 30% hydrogen Number Name Date peroxide was then added with vigorous agitation, 2,068,424 Mark ------Jan. 19, 1937 during about 25 min. The mixture was allowed 2,200,437 WoSS ------May 14, 1940 to stand, with occasional agitation, for about 15 60 2,339,058 D'Alelio ------Jan. 11, 1944 minutes additional, after which the organic layer 1,754,914 Stoddard ------Apr. 15, 1930 was decanted off, weighed and titrated. Yield FOREIGN PATENTS 41 g. Active oxygen content 2.0%. This corre sponds to 6.05 g. acetyl peroxide which is 51% of Number Country Date the theoretical yield. 39,107 Austria ------Oct. 11, 1909 Eacample III OTHER REFERENCES To 50 ml. dioctyl phthalate was added 10 g. Beilstein, "Handbuch der Organischen Cheni,” acetic anhydride and, after cooling to -5° C., 4th ed., vol.II, page 170.