JP3803663B2 - Method for producing epoxy compound - Google Patents

Description

  The present invention relates to a method for producing an epoxy compound by oxidation of olefins using polyacids or specific metal oxides and hydrotalcites as a catalyst. Specifically, hydrotalcite is made into a dispersed phase of polyacids or metal oxides to promote the generation of active species of polyacids or metal oxides by hydrogen peroxide, which is an oxidant, and the reaction rate and reaction rate in a solvent-free system. The present invention relates to a method for producing an epoxy compound with improved selectivity.

  Epoxy compounds are useful compounds as intermediates and raw materials in the production of various industrial products, pharmaceuticals, agricultural chemicals, etc., but in general, in the method for producing epoxy compounds using olefins and hydrogen peroxide, the conversion rate of olefins And the selectivity of the epoxy compound is low. For this reason, a production method using a specific catalyst has been proposed.

  For example, in Patent Document 1 and Non-Patent Document 1, a salt of a quaternary ammonium ion derived from a quaternary ammonium compound or a nitrogen-containing quaternary compound with a Group V element of the periodic table and a heteropolyacid of tungsten. Alternatively, a method of reacting an olefin and a hydrogen peroxide solution with a halogenated hydrocarbon as a solvent using a catalyst comprising the peroxide has been disclosed. This is a method for producing an epoxy compound in a two-phase system of water and an organic solvent. However, halogen-based organic solvents such as chloroform or dichloromethane, which are harmful to the global environment, are used.

In Patent Document 2, due to needs for the global environment, an epoxy compound composed of hydrogen peroxide and olefins in the presence of α-aminomethylphosphonic acid, tungstic acid and a phase transfer catalyst in a non-halogen organic solvent such as an aromatic hydrocarbon is used. A synthetic method has been disclosed. It is stated that the aqueous phase containing the catalyst can be separated and reused for the same substrate. However, since the present invention uses a low-concentration hydrogen peroxide solution, it is difficult to recover the catalyst after the reaction, reuse it, or treat the waste water remaining after the reaction.
JP-A-62-234550 JP-A-8-27136 Journal of Organic Chemistry "Vol. 53, page 3587 (1988)"

  In light of the above-mentioned present situation, the present invention makes it easy to prepare a catalyst phase comprising polyacids or metal oxides and hydrotalcites, and does not require an organic solvent that adversely affects the global environment, and is easy to handle urea. -By using hydrogen peroxide, it is possible to easily convert an olefin to an epoxy compound in a solvent-free system, from a high degree of conversion and selectivity, and from a reusable catalyst. The manufacturing method of the epoxy compound of this is provided.

  In order to solve the above-mentioned problems, the present inventors have intensively studied a solid-phase reaction process different from the conventional reaction system, and as a result, completed the present invention. That is, the present invention is characterized in that olefins are reacted with hydrogen peroxide in the presence of a catalyst comprising (a-1) polyacids or (a-2) specific metal oxides and (b) hydrotalcites. This is a method for producing an epoxy compound.

  According to the production method of the present invention, in a solvent-free system that does not require an organic solvent in the synthesis of an epoxy compound, hydrotalcite that is less harmful enough to be widely used as a gastrointestinal drug as an antacid is used as a solid dispersed phase. Since the reaction can proceed, the epoxy compound can be synthesized under conditions with a very low environmental load. In addition, high-purity epoxy compounds can be efficiently produced with very simple equipment industrially. The epoxy compound obtained by the present invention is useful as an intermediate or raw material in the production of various industrial products, medicines, agricultural chemicals and the like.

  According to this invention, the manufacturing method of the epoxy compound described in following (1)-(10) is provided.

(1) At least one polylactic acid or (a-2) tungsten, molybdenum selected from the group consisting of metal isopolyacids, heteropolyacids, and salts of these metals, wherein (a-1) is tungsten, molybdenum and vanadium And an oxide of a metal selected from the group consisting of vanadium, its acid or its salt (component a) and (b) hydrotalcite (component b) in the presence of a catalyst comprising olefins in the form of a solid powder A method for producing an epoxy compound comprising reacting with hydrogen peroxide.

(2) (a-1) is tungsten down, the isopoly acids, heteropolyacids acids and a method for producing an epoxy compound of at least one poly acids selected from the group consisting of salts of these acids (1),.

(3) The method for producing an epoxy compound according to (1), wherein (a-2) is at least one metal oxide selected from the group consisting of an oxide of tungsten, an acid thereof, and a salt of the acid.

(4) The polyacid of (a-1) is a heteropolyacid, and the epoxy compound of the above (1) containing phosphorus, boron, silicon, germanium, lanthanoid, nickel, iron, cobalt or ruthenium as the hetero atom Production method.

(5) The polyacid of (a-1) is an isopolyacid or a heteropolyacid, and the counter cation is an organic cation of tetrabutylammonium, butylammonium, benzyltrimethylammonium or cetylpyridinium, or ammonium, potassium, sodium or The method for producing an epoxy compound according to (1), which is an inorganic cation of calcium.

(6) The hydrotalcite of (b) is represented by the following formula (1): (M ²⁺ ) _1-x (M ³⁺ ) _x (OH) ₂ (A ⁿ⁻ ) _{x / n} · aH ₂ O (1)
(Wherein, M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, A ^n-represents an n-valent anion, and each of x and a 0 <x <0.5 And 0 ≦ a <1). The method for producing an epoxy compound according to (1), comprising at least one selected from the group consisting of:

(7) In the hydrotalcite of formula (1), M ²⁺ is at least one selected from the group consisting of Mg ²⁺ , Ca ²⁺ and Zn ²⁺ , and M ³⁺ is at least one selected from Al ³⁺ and Fe ³⁺ . , ^{A n-is _{OH -, ClO 4 -, NO}} 3 -, SO 4 2-, CO 3 2-, SiO 3 2-, HPO 4 2-, PO 4 3- and _CH 3 COO ^- selected from the group consisting of (6) The manufacturing method of the epoxy compound which consists of said at least 1 type.

Hydrotalcite of (8) ^{(1), M 2+} is Mg ^2+, method for producing an epoxy compound ^{M 3+} is Al ^{3+, A n-} is _CO ^{3 2-,} comprising the (6).

(9) The method for producing an epoxy compound according to (1), wherein the reaction is carried out substantially in the absence of a solvent.
(10) The method for producing an epoxy compound according to (1), wherein the hydrogen peroxide is a urea-hydrogen peroxide complex.

  The present invention will be described in detail below.

  In the method for producing an epoxy compound of the present invention, a combination of the a component and the b component is used as a catalyst. Among these, the component a is (a-1) a polyacid or (a-2) a metal oxide selected from the group consisting of tungsten, molybdenum and vanadium, an acid thereof or a salt of the acid. On the other hand, component b is hydrotalcite.

The polyacids (a-1) are particularly preferably polyacids (a) containing at least one of tungsten, molybdenum, and vanadium, and particularly preferably isopolytungstic acid, tungstic acid, heteropolytungstic acid, and heteropolymolybdic acid. The type and Dawson type are also included. Polyacids usually exist as anions, and to neutralize the charge, alkali metals such as Na ⁺ and K ⁺ , alkaline earth metals such as Mg ²⁺ and Ca ²⁺ , ammonium ions, and quaternary ammonium ions Or the catalyst which consists of at least 1 type of polyacids selected from the group which consists of the salt of the ion of the quaternary ammonium type compound which has a nitrogen-containing heterocyclic ring is mentioned. More preferred examples include quaternary ammonium compounds having Na ⁺ , K ⁺ , ammonium and pyridine rings. In addition, examples of the hetero atom include phosphorus, boron, silicon, germanium, and cobalt. Commercially available products can be used for these polyacids. Also, for example, Patent Publication 2002-532378 or M.I. T.A. Inorganic chemistry by Pope et al., Vol. 6 1147. It can also be synthesized according to page (1967).

  Moreover, as (a-2), the metal oxide selected from the group which consists of tungsten, molybdenum, and vanadium, its acid, or its acid salt is used. The salt is preferably a potassium, sodium or ammonium salt of a metal acid. (A-2) is particularly preferably an oxide of tungsten, an acid thereof or a salt of the acid.

(B) Hydrotalcites include the following formula (1): (M ²⁺ ) _1-x (M ³⁺ ) _x (OH) ₂ (A ⁿ⁻ ) _{x / n} · aH ₂ O (1)

(Wherein, M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, A ^n-represents an n-valent anion, and each of x and a 0 <x <0.5 a 0 ≦ a <hydrotalcite comprising at least one member selected from the group consisting of 1 shows the range of), at least one preferably, M ²⁺ is selected from the group consisting of Mg, Ca and Zn , at least one M ³⁺ is selected from, Al and Fe, A ^{n-is _{OH -, ClO 4 -, NO}} 3 -, SO 4 2-, CO 3 2-, SiO 3 2-, HPO 4 2- , PO ₄ ^3- and CH3 COO ^- more consisting of at least one consisting of hydrotalcite selected from the group, more preferably M ²⁺ is Mg, M ³⁺ is Al, A ^n-is CO ₃ ^2- in shown Hydrotalcite is used. As a method for synthesizing hydrotalcites, for example, a synthesis method disclosed in JP-B-47-32198 can be used.

  Preparation of the catalyst consisting of a component and b component (hydrotalcite) is only required to mix them. For example, the powder of polyacids is added to the dried hydrotalcite in advance and the powders are well stirred. Mix. It is preferable to disperse the a component as uniformly as possible on the surface of the b component (hydrotalcite). Therefore, the powder of the a component is preferably fine particles. For example, as a preferable particle size, an average particle diameter by electron microscope observation is 10 μm or less, and more preferably 5 to 0.01 μm. As another method, a method of adding the a component in the form of an aqueous solution to the dried hydrotalcite and stirring and mixing it may be used. Furthermore, a method of adding a small amount of component a when preparing hydrotalcites may be used.

The particle size of hydrotalcite is not particularly limited. For example, dry powder obtained by kneading dry powder of hydrotalcite with purified water and then extruding and granulating it can be used as fine particles it can. The normal use range is 5 mm to 0.1 μm, preferably 1 mm to 5 μm, and more preferably 100 μm to 10 μm. 500m ² / g~5m ² / g, the surface area of the hydrotalcite compound BET method is preferably from 300m ² / g~10m ² / g, more preferably 250m ² / g~50m ² / g.

  The mixing ratio of the a component and the b component is in the range of 0.001 mol to 0.1 mol, preferably 0.005 mol to 0.05 mol of the a component per mol of the hydrotalcite of the b component.

  The mixing method is not particularly limited, but it is preferable that the temperature does not exceed 200 ° C. Preferably, the temperature is from 0 ° C to 100 ° C. In particular, when the salt of the component a is a salt of a quaternary ammonium compound having a quaternary ammonium ion or a nitrogen-containing heterocyclic ring, it is preferable not to exceed 100 ° C. The mixing stirrer may be any method as long as it can uniformly disperse the component a. For example, a mixer equipped with a high-speed stirring blade such as a Henschel mixer, a V-type mixer, a ribbon blender, or the like can be used. .

  Examples of the olefins in the present invention include aliphatic olefinically unsaturated hydrocarbons, alicyclic olefinic hydrocarbons, and aromatic olefinic hydrocarbons. Specifically, ethylene, propylene, butene, pentene, hexene, heptene, octene, nonene, undecene, dodecene, tridecene, tetradecene, pentadecene, eicosene, diisobutylene, propylene tri- or tetramer, cycloalkene or cyclopolyene (for example, cyclopentene) , Cyclohexene, cycloheptene, cyclooctene, cyclodecene, cyclopentadiene, cyclooctadiene, cyclododecatriene, etc.), dicycloalkapolyene (eg, dicyclopentadiene, tetrahydroindene, etc.), alkylene dicycloalkane (eg, methylenecyclopropane, methylenecyclopentene, etc.) , Methylenecyclohexene and the like) and vinylcycloalkene (eg vinylcyclohexene and the like). These may be used as a mixture of two or more.

  The addition amount of the olefin with respect to component a is 1000 mol to 10 mol, preferably 500 mol to 50 mol, per mol of component a. If the amount exceeds 1000 mol, the conversion rate of the epoxy compound decreases, and the oxidation efficiency of hydrogen peroxide decreases. On the other hand, if it is 10 mol or less, the production efficiency decreases.

The oxidizing agent used in the present invention is solid powder hydrogen peroxide . Of these, a urea-hydrogen peroxide complex is preferable. The urea-hydrogen peroxide complex is a solid powder, is safe as long as it is sealed and stored at room temperature, and is much easier to handle than hydrogen peroxide solution. Also, there are no restrictions on the means of transportation. The preferred particle size of this composite is 1 μm to 300 μm. The hydrogen peroxide content is 25 to 40 wt%, and usually about 35 wt% is used.

  As a method for synthesizing the urea-hydrogen peroxide complex, for example, urea is dissolved in 30 wt% hydrogen peroxide water, heated to 40 to 70 ° C., cooled, and recrystallized. Regarding these production methods, C.I. Lu, E .; W. Hughes, P.M. Giguere, Journal of American Chemical Society, Vol. 63, p. 1507.

  In the method for carrying out the present invention, the hydrotalcite (b) of formula (1) and the component a are introduced into a reaction vessel, and then olefins are introduced and mixed well with stirring. Thereafter, an oxidizing agent such as urea-hydrogen peroxide powder is added and mixed uniformly, and then the reaction is allowed to proceed.

  The reaction temperature is preferably in the range of 0 ° C to 100 ° C. More preferably, it is 10 degreeC-50 degreeC. If the reaction temperature is higher than 100 ° C., the decomposition of hydrogen peroxide becomes stronger, and the selectivity of the epoxy compound also decreases. When the reaction temperature is less than 0 ° C., the reaction rate tends to decrease remarkably. The reaction time varies depending on the types and amounts of component a, component b (hydrotalcite), olefin, hydrogen peroxide used, and temperature, and is usually in the range of several minutes to 50 hours.

After completion of the reaction, the obtained epoxy compound is extracted and separated with a hydrocarbon solvent having a low environmental load. Alternatively, the reaction mixture in the reaction vessel can be isolated by heating and distillation under reduced pressure. By introducing olefin and urea-hydrogen peroxide again into the catalyst after the reaction and repeating the same operation as the first time, the catalyst can be reused. The catalyst activity may be reduced by increasing the number of uses. The reason is considered to be that urea accumulates after the consumption of hydrogen peroxide. In that case, it is possible to remove urea by washing with water, acetone or an alcohol mixed solution, or baking at 200 ° C. to 300 ° C. I can do it. In the calcined hydrotalcite, the aH ₂ O of the formula (1) may be significantly reduced. In such a case, the initial catalytic activity can be recovered by absorbing moisture.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Examples 1-6
In a glass test tube with a screw cap, a commercially available hydrotalcite (Kyowa Chemical Industry Co., Ltd.) having a BET represented by the chemical formula Mg ₆ Al ₂ (OH) ₁₆ CO ₃ .4H ₂ O of 110 m ² / g and an average particle size of 17 μm. KW500) 0.25g, a component 0.005mmol amount was shaken and mixed. To this solid mixture, 0.5 mmol of cyclooctene containing n-pentadecane as an internal standard substance was added and mixed. Furthermore, after adding 1.25 mmol of commercially available urea-hydrogen peroxide having a hydrogen peroxide content of 35 wt% in terms of hydrogen peroxide and mixing well, the mixture was allowed to stand at 25 ° C. for 24 hours. The reaction mixture was extracted with pentane and the extract was analyzed using gas chromatography. The conversion of cyclooctene after 24 hours at 25 ° C. and the selectivity of the resulting epoxide (epoxycyclooctane) are shown in Table 1. In either case, epoxides were selectively produced corresponding to the conversion rate of the substrate, and no by-products were produced.

Comparative Examples 1-6
All were carried out similarly to Examples 1-6 except not using hydrotalcite (KW500).

  In the case of a catalyst that does not contain hydrotalcite, as shown in Comparative Examples 1 to 6, the progress of the reaction is hardly observed, whereas in the case of a catalyst that contains hydrotalcite (KW500), epoxidation is greatly increased. Progressed.

Comparative Example 7
In Example 3, all tests were performed in the same manner as in Example 3 except that active magnesium oxide (BET surface area of 150 m ² / g) was used instead of hydrotalcite (KW500). As a result of analysis by gas chromatography, the conversion of cyclooctene was 10.0%, and the yield of epoxycyclooctane was 10.0%.

Comparative Example 8
In Example 3, all tests were performed in the same manner as in Example 3 except that montmorillonite (BET surface area 200 m ² / g) was used instead of hydrotalcite (KW500). As a result of analysis by gas chromatography, the conversion of cyclooctene was 35.5%, and the yield of epoxycyclooctane was 35.5%.

Comparative Example 9
In Example 3, all tests were performed in the same manner as in Example 3 except that fluoroapatite Ca10 (PO4) 6F2 (BET surface area 10 m ² / g) was used instead of hydrotalcite (KW500). As a result of analysis by gas chromatography, the conversion of cyclooctene was 28.0%, and the yield of epoxycyclooctane was 28.0%.

Example 7
Reuse of solid catalyst phase (NH ₄ ) ₃ [PW ₁₂ O ₄₀ ] / KW-500 in epoxidation reaction of cyclooctene

(1) 0.2950 g (350 μL, 2.5 mmol) of cyclooctene to a solid mixture of hydrotalcite KW-500 1.25 g and (NH ₄ ) ₃ [PW ₁₂ O ₄₀ ] 0.0737 g (0.025 mmol, 1 mol%) ) And stir well. To this, 0.5904 g (6.25 mmol) of urea-hydrogen peroxide (Urea-H ₂ O ₂ ) was added and stirred again, and then allowed to stand at 25 ° C.

  After 24 hours, the solid reaction mixture was extracted with pentane (10 mL × 3 times) and the solvent was distilled off to obtain 0.280 g of a colorless solid. Crude yield 89% (GC purity 93%).

(2) The solid catalyst phase after extraction (including (NH ₄ ) ₃ [PW ₁₂ O ₄₀ ] and hydrotalcite) was dried under reduced pressure overnight. This solid catalyst phase was impregnated with 0.2940 g (350 μL, 2.5 mmol) of cyclooctene and stirred well, and then 0.5902 g (6.25 mmol) of urea-hydrogen peroxide (Urea-H ₂ O ₂ ) was added. The mixture was stirred again and allowed to stand at 25 ° C.

After 24 hours, as in the first time, the solid reaction mixture was extracted with pentane (10 mL × 3 times) and the solvent was distilled off to obtain 0.282 g of a colorless solid. Crude yield 89% (GC purity 93%).
Thus, even when the catalyst was reused, almost the same high catalytic activity was exhibited.

Example 8
Recycling of the solid catalyst phase in the epoxidation reaction of cyclooctene (WO ₃ / KW-500)

Reuse of the solid catalyst phase is the same as in Example 7 except that WO ₃ (0.25 mmol, 10 mol%) is used instead of the polyacid (NH ₄ ) ₃ [PW ₁₂ O ₄₀ ] in Example 7. Repeatedly. The conversion rate of cyclooctene after 24 hours at 25 ° C. was 71.6% (first time), 91.0% (second time), 90.7% (third time), 2.4% (fourth time), 70 4% (5th time).

Example 9
Hydrotalcite (KW500) 0.25 g, polyacid (NH ₄ ) ₃ [PW ₁₂ O ₄₀ ] 0.01 mmol amount of solid mixture was added 0.5 mmol of 1-decene containing n-pentadecane as an internal standard substance, Mixed. Further, 1.25 mmol of urea-hydrogen peroxide was added and mixed well, and then allowed to stand at 25 ° C. for 24 hours. The reaction mixture was extracted with pentane and the extract was analyzed using gas chromatography. After 48 hours at 25 ° C., 64.1% formation of the corresponding 1,2-epoxydecane was observed.

Example 10
To a solid mixture of 0.25 g of hydrotalcite (KW500) and 0.05 mmol of a component H ₂ WO _4, 0.5 mmol of cyclododecene containing n-pentadecane as an internal standard substance was added and mixed. Further, 1.25 mmol of urea-hydrogen peroxide was added and mixed well, and then allowed to stand at 25 ° C. for 24 hours. The reaction mixture was extracted with pentane and the extract was analyzed using gas chromatography. After 24 hours at 25 ° C., the conversion was 41.7% and the yield of the corresponding epoxycyclododecane was 41.7%.

Example 11
By making hydrotalcite (component b) into a dispersed phase of polyacid (component a), it reacts with urea-hydrogen peroxide, which is an oxidant, in a solvent-free system and under solid-phase conditions to produce an active species of polyacid It is clear from the measurement of the solid nuclear magnetic resonance spectrum and the infrared spectrum.

For example, after adding 0.2 mmol of hydrotalcite (KW500) and 0.1 mmol of urea-hydrogen peroxide to a solid mixture of polyacid (NH ₄ ) ₃ [PW ₁₂ O ₄₀ ] 0.1 mmol, mix well. And left at 25 ° C. ³¹ P solid nuclear magnetic resonance (NMR) spectrum and infrared spectrum were measured at regular time intervals. FIG. 1 and FIG. 2 show changes in spectrum over time.

^{In the 31} P solid state NMR spectrum, a new peak marked with * is derived from the generated active species. Active species are generated within 30 minutes after the start of the reaction. It can be seen from the chemical shift value of the peak that it is different from the active species in the conventional liquid phase reaction. Also in the infrared spectrum, it can be seen that active species are generated as fast as NMR, and that the active species does not vary greatly from the polyacid cluster structure.

In Example 11 of the present invention, the catalyst in the urea - shows the ³¹ time course of P solid NMR spectrum in the case of mixed hydrogen peroxide. In the said Example 11, the time-dependent change of the infrared spectrum of a polyacid is shown.

Claims (10)

(A-1) at least one polyacid selected from the group consisting of metal isopolyacids, heteropolyacids, and salts of these acids, consisting of tungsten, molybdenum and vanadium, or (a-2) from tungsten, molybdenum and vanadium Oxidation of olefins in the form of a solid powder in the presence of a catalyst comprising an oxide of a metal selected from the group consisting of: an acid thereof or a salt thereof (component a) and (b) a hydrotalcite (component b) A method for producing an epoxy compound, characterized by reacting with hydrogen. (A-1) isopoly acids of tungsten emissions, heteropolyacids acids, and method for producing an epoxy compound according to claim 1 is at least one poly acids selected from the group consisting of salts of these acids. The method for producing an epoxy compound according to claim 1, wherein (a-2) is at least one metal oxide selected from the group consisting of an oxide of tungsten, an acid thereof and a salt of the acid. The method for producing an epoxy compound according to claim 1, wherein the polyacids of (a-1) are heteropolyacids, and the heteroatoms include phosphorus, boron, silicon, germanium, lanthanoid series, nickel, iron, cobalt, or ruthenium. The polyacid of (a-1) is an isopolyacid or heteropolyacid, and the counter cation is an organic cation of tetrabutylammonium, butylammonium, benzyltrimethylammonium or cetylpyridinium, or an inorganic of ammonium, potassium, sodium or calcium The method for producing an epoxy compound according to claim 1, which is a cation. The hydrotalcites of (b) are represented by the following formula (1): (M ²⁺ ) _1-x (M ³⁺ ) _x (OH) ₂ (A ⁿ⁻ ) _{x / n} · aH ₂ O (1)
^{(Wherein, M 2+} is a divalent metal ^{ion, M 3+} is a trivalent metal ^{ion, A n-represents} an n-valent anion, and each of x and a 0 <x <0.5, 0 The method for producing an epoxy compound according to claim 1, comprising at least one selected from the group consisting of ≦ a <1. In the hydrotalcite of the formula (1), M ²⁺ is at least one selected from the group consisting of Mg ²⁺ , Ca ²⁺ and Zn ²⁺ , M ³⁺ is at least one selected from Al ³⁺ and Fe ³⁺ , ^{An −} Is at least selected from the group consisting of OH ⁻ , ClO ₄ ⁻ , NO ₃ ⁻ , SO ₄ ²⁻ , CO ₃ ²⁻ , SiO ₃ ²⁻ , HPO ₄ ²⁻ , PO ₄ ³⁻ and CH ₃ COO ^−. The method for producing an epoxy compound according to claim 6 comprising one kind. Method for producing a hydrotalcite of formula (1) ^{is, M 2+} is Mg ^{2+, M 3+} is Al ^{3+, A n-} is _CO ^{3 2-,} epoxy compound according to claim 6 consisting of. The method for producing an epoxy compound according to claim 1, wherein the reaction is carried out substantially in the absence of a solvent. The method for producing an epoxy compound according to claim 1, wherein the hydrogen peroxide is a urea-hydrogen peroxide complex.

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