Acetylacetonate is an essential class of organometallic compounds, and its many unique properties have attracted widespread attention. It is widely used in chemical, petroleum, pharmaceutical, electronics, materials, machinery, and other fields. The synthesis methods of acetylacetonate mainly include a liquid phase and a solid phase. The research and development of various acetylacetonate synthesis processes and their applications have become hot topics. As early as the 1960s, scientists studied the use of transition metal acetylacetonate in the polymerization of vinyl monomers.
Method for preparing acetylacetonate
Acetylacetone has two carbonyl-linked methylene groups (-CH2-), one of which (on the hydroxyl group) is more comfortable to remove because of the negative charge of the resulting carbanion is dispersed by two oxygen atoms through conjugation. Above, this conjugated structure is very stable, and therefore, acetylacetone is a monobasic weak acid having a pKa of 8.9.
First, the liquid phase method.
The liquid phase method is a relatively synthetic method for the synthesis of acetylacetonate.
Mechanical analysis
In the liquid phase method, a soluble metal salt is first reacted with an alkali solution to obtain a hydroxide precipitate of a metal salt, and then the hydroxide is reacted with acetylacetone to obtain an acetylacetonate salt. Acetylacetone is a weak, weak acid, and the reaction of the hydroxide is an acid-base neutralization reaction. Acetylacetone is usually a mixture of two mentors of enol and ketone. It is in dynamic equilibrium. As the reaction proceeds, the enol form is continuously reduced, which promotes the continuous conversion of the ketone to the enol form. Go on.
Process flow
Firstly, the soluble metal salt is prepared into a specific concentration of the aqueous solution, and a specified level of NaOH solution is added to it to cause an acid reaction to form a metal hydroxide precipitate. The hydroxide is filtered, and then the hydroxide and acetylacetone are stirred. The mixture is heated under reflux and reacted under a specific temperature for a certain period, cooled, filtered to obtain a precipitate of acetylacetone metal salt, and purified to purchase a product. The reaction of raw material may also be a metal oxide. The process comprises the steps of reacting acetylacetone, metal oxide, and catalyst in a specific ratio under stirring and heating to a particular temperature for a certain period, cooling, filtering to obtain acetylacetonate, and purifying to purchase a product.
Second, the robust phase method.
The robust phase method is a synthetic method for studying relatively hot acetylacetonate in recent years. The technique has many advantages: no solvent, fast reaction, mild conditions, simple operation, high selectivity, high yield, low energy consumption, and environmental friendliness. It has universal applicability and can eliminate the adverse effects of solvent on functional complexes, and avoids the shortage of water as a solvent in the liquid phase method, prolonged reaction time and low yield.
Mechanical analysis
Acetylacetone is a weak, weak acid and cannot react directly with inorganic metal salts. The solid base is here first reacted with weakly acidic acetylacetone to form pure metal salts of acetylacetone. In such compounds, chelation is not dominant, and they have typical salt properties. The reaction of acetylacetone with a solid base is an acid-base neutralization reaction in which acetylacetone loses hydrogen to form acac, and acac encounters a positively charged metal ion in the metal salt to create a stable acetylacetonate.
Process flow
The solid base and acetylacetone are added to the mortar in a specific ratio and ground for a few minutes, and then a certain amount of metal salt is added. After adding the metal salt, it is ground into a thin paste, and further grinding into a solid powder. After the solid phase reaction for a while, The unreacted material was dissolved by soaking in water, and the acetylacetone salt was obtained by filtration, and purified to purchase a product.
Application of acetylacetonate
Acetylacetonate is widely used in chemical, petroleum, pharmaceutical, electronics, materials, machinery, and agriculture industries, mainly for catalytic, stabilization, and promotion.
1 Synthetic catalyst
Calcium acetylacetonate is a catalyst for synthesizing DMA by transesterification of methyl methacrylate (MMA) and dimethylaminoethanol (DMAE); zinc acetylacetonate is a precursor of sorbic acid formed by the condensation reaction of crotonaldehyde with ketene Ester catalyst; iron acetylacetonate can be used as a photodegradable high-efficiency photocatalyst for plastics. The research of this product is of considerable significance in industrial production and environmental chemistry; manganese acetylacetonate is a homogeneous catalytic oxidation catalyst, and manganese acetylacetonate is loaded to MCM. -41 On the carrier, the supported catalyst can be used to catalyze the oxidation of limonene, and the catalyst can be reused; aluminum acetylacetonate is a lipophilic monoclinic crystal with excellent water resistance. It is widely used as olefin polymerization and ring. Oxygen resin curing, silane polymerization catalyst, nickel acetylacetonate can be used not only as an oligomerization and polymerization catalyst for non-polar monomers such as ethylene, propylene, styrene, diolefins, cycloolefins but also as methyl methacrylate, a polymerization catalyst for polar monomers such as caprolactone and norbornene.
2 Stabilizer
Calcium acetylacetonate is a halide heat stabilizer such as rigid PVC, which has a remarkable synergistic effect with stearyl methane and dibenzoylmethane.
3 Promoter
Calcium acetylacetonate is an accelerator for resin hardening; a high-performance resin can be obtained by using an acetylacetonate-based transition metal complex as a promoter and a cyanate-modified epoxy resin; chromium acetylacetonate is an epoxy anhydride system. The latent accelerator, which is used in the epoxy anhydride system, has the advantages of short gelation time, good storage stability, and excellent mechanical and electrical properties.
4 Synthesis of raw materials
Indium acetylacetonate is one of the raw materials for the preparation of indium tin oxide transparent conductive film (ITO) by MO-CVD. ITO film is widely used in liquid crystal display glass, curtain wall glass, aircraft, and the automobile because of its characteristics of transparency and good electrical conductivity. Anti-fog windshield, etc.; aluminum acetylacetonate can be combined with polysilicon carbosilane (PSCS) to produce the best high-temperature resistant SiC (A1) ceramic fiber Tyranno SA precursor polyaluminum carbosilane (PACS), A cerium-doped zirconium-cerium-aluminum (ZBLA) fluoride thin-film optical waveguide was prepared from cerium hydroxide, zirconium acetylacetonate, cerium hydroxide, and cerium chloride.
5 Other uses
Calcium acetylacetonate can act as a resin crosslinker, resin, rubber additive, superconducting film, hot wire reflective glass, transparent conductive film-forming agent; adding aluminum acetylacetonate in low molecular weight hydrosilylation reaction can effectively prevent platinum Catalyst poisoning [17]; acetylacetonate oxime has a polymerization effect on caprolactone and lactide, and the obtained high molecular weight crystalline polycaprolactone and amorphous polylactide have excellent biocompatibility. The biomedical field has a wide range of uses; the complex formed by titanium acetylacetonate and monochlorodiyl aluminum catalyzes the polymerization of styrene.
The synthesis of acetylacetonate is divided into a liquid phase method and a robust phase method. The liquid phase method generally uses soluble metal salt, sodium hydroxide solution, and acetylacetone as raw materials to synthesize by causticization and neutralization reaction; robust phase method uses metal salt, stable base, and acetylacetone as raw materials to directly integrate by solid-phase grinding at room temperature. The currently widely used process is the liquid phase process. The use of acetylacetonate is extensive, and it is essential to study the synthetic route of acetylacetonate and the new method of acetylacetonate.
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