Catalyst carboxylic acid salt

Unsymmetrical as well as symmetrical anhydrides are often prepared by the treatment of an acyl halide with a carboxylic acid salt. The compound C0CI2 has been used as a catalyst. If a metallic salt is used, Na , K , or Ag are the most common cations, but more often pyridine or another tertiary amine is added to the free acid and the salt thus formed is treated with the acyl halide. Mixed formic anhydrides are prepared from sodium formate and an aryl halide, by use of a solid-phase copolymer of pyridine-l-oxide. Symmetrical anhydrides can be prepared by reaction of the acyl halide with aqueous NaOH or NaHCOa under phase-transfer conditions, or with sodium bicarbonate with ultrasound. 

Alternatively, esterification of carboxylic acid can be carried out in aqueous media by reacting carboxylic acid salts with alkyl halides through nucleophilic substitutions (Eq. 9.10).20 The reaction rate of alkyl halides with alkali metal salts of carboxylic acids to give esters increases with the increasing concentration of catalyst, halide, and solvent polarity and is reduced by water. Various thymyl ethers and esters can be synthesized by the reactions of thymol with alkyl halides and acid chlorides, respectively, in aqueous medium under microwave irradiation (Eq. 9.11).21 Such an esterification reaction of poly(methacrylic acid) can be performed readily with alkyl halides using DBU in aqueous solutions, although the rate of the reaction decreases with increasing water content.22... 

For the reaction of TDI with a polyether triol, bismuth or lead compounds can also be used. However, tin catalysts are preferred mainly because of their slight odor and the low amounts required to achieve high reaction rates. Carboxylic acid salts of calcium, cobalt, lead, manganese, zinc, and zirconium are employed as cocatalysts with tertiary amines, tin compounds, and tin—amine combinations. Carboxylic acid salts reduce cure time of rigid foam products. Organic mercury compounds are used in cast elastomers and in RIM systems to extend cream time, ie, the time between mixing of all ingredients and the onset of creamy appearance. 

Precipitation of the catalyst from the reaction medium, followed by filtration, as in the cobalt-based hydroformylation process (see Section 5.4). Here cobalt is removed from the reaction products in the form of one of its salts or as the sodium salt of the active carbonyl catalyst. The aqueous salts can be recycled directly, but sometimes they are first converted into an oil-soluble long-chain carboxylic acid salt, such as the corresponding naphthenate, oleate, or 2-ethylhexanoate. 

The reaction is of practical importance in the vulcanization of silicone mbbers (see Rubbercompounding). Linear hydroxy-terminated polydimethylsiloxanes are conveniently cross-linked by reaction with methyldiethoxysilane or triethoxysilane [998-30-1]. Catalysts are amines, carboxylic acid salts of divalent metals such as Zn, Sn, Pb, Fe, Ba, and Ca, and organotin compounds. Hydroxy-terminated polysiloxanes react with Si—H-containing polysiloxanes to... 

Active catalysts for butadiene polymerization are obtained from aluminium alkyl halides and soluble Co and Co salts and complexes. The structure of the organic grouping attached to the cobalt is not important, but compounds most widely employed are acetylacetonates and carboxylic acid salts such as the octoate and naphthenate. The activity of the catalyst and structure of the polymer are affected by the groupings in the complex. Catalysts from aluminium trialkyls and cobalt salts other than halides are relatively unstable and give syndiotactic 1,2-polybutadiene. If halogens are present, e.g., from CoClj or CoBrj,... 

As stated above, Knoevenagel condensations can occur on catalysts combining acidic and basic sites. A well-known system is the combination of an amine and its carboxylic acid salt. Such catalysts seem to activate the carbonyl substrates, usually by imine or enamine formation, and the activated substrate is subsequently activated by protonation. The base assists the deprotonation of a methylene-active compound, forming a carbanion, followed by nucleophilic attack on the proto-nated imine (Scheme 3A). 

These novel skeletal copper catalysts have significant potential for use in a wide range of organic synthesis reactions including those in which high caustic concentrations are involved such as in the dehydrogenation of primary alcohols to form carboxylic acid salts. 

Some industrial organic synthesis reactions take place in the presence of aqueous caustic soda. A typical exanqile is the dehydrogenation of amino alcohols to amino carboxylic acid salts, which is typically conducted at 1.0 MPa and 393K-483K in a concentration of caustic up to 50wt%. Under such harsh conditions, most supported copper catalysts cannot be used due to dissolution of... 

This section contains metal-organic compounds, ammonium and metal derivatives of organic alcohols, amines and carboxylic acids (salts), as well as ionophores that form complexes with metal ions. Note that there is a large number of metal-organic catalysts, and reagents for preparing some of these catalysts, in Chapter 6, and can be considered as an extension of this section. (For Introduction see p 555.)... 

The new Monsanto process makes use of a copper catalyst, which is used to reduce diethanolamine to DSIDA, the intermediate to Roundup (see Fig. 9.27). This process totally eliminates the use of ammonia, hydrogen cyanide, and formaldehyde, is free of contaminants and byproducts, and hence does not require further purification steps. The stream can be recycled after filtration of catalyst. Monsanto s process can also be used in the production of other amino acids such as glycine through reduction and is a general method for conversion of primary alcohols to carboxylic acid salts. The development of this technology for processes pertaining to the agricultural, commodity, specialty, and pharmaceutical sectors would have a pronounced impact on the environment. 

An alternative solution to the limitations of the aryl carboxylate salts mentioned previously is a new bimetalhc catalyst system that allows the replacement of aryl hahdes by aryl triflates [14, 67]. The reaction proceeds efficiently with Pdl, Tol-BINAP, Cu O, and 1,10-phenanthroline, affording the corresponding unsymmetrical biaryls (Scheme 22.47). It is noteworthy that the reaction is generally applicable to aromatic carboxylic acid salts, regardless of their substitution pattern. The use of microwave irradiation has proved beneficial for this ARCIS reaction, since under these conditions the Pd(ll) catalyst is almost instantaneously reduced to Pd(0) [68]. Similarly, substituted aryl tosylates have been found to be suitable substrates in decarboxylative couphng reactions with a fuU range of benzoic acids (Scheme 22.47) [69]. 

By direct esterification or transesterification of dicarboxylic acids with various glycols in the presence of monocarboxylic acids and alcohols, oligoesters are produced. As catalysts, benzene- and toluenesulfonic acids are used as well as carboxylic acids salts or tetrabutoxytitane. The main use of these is in the plasticizing of various plastics [24,25]. 

Practically all pyridazine-carboxylic and -polycarboxylic acids undergo decarboxylation when heated above 200 °C. As the corresponding products are usually isolated in high yields, decarboxylation is frequently used as the best synthetic route for many pyridazine and pyridazinone derivatives. For example, pyridazine-3-carboxylic acid eliminates carbon dioxide when heated at reduced pressure to give pyridazine in almost quantitative yield, but pyridazine is obtained in poor yield from pyridazine-4-carboxylic acid. Decarboxylation is usually carried out in acid solution, or by heating dry silver salts, while organic bases such as aniline, dimethylaniline and quinoline are used as catalysts for monodecarboxylation of pyridazine-4,5-dicarboxylic acids. 

The isocyanurate reaction occurs when three equivalents of isocyanate react to form a six-membered ring, as shown in the fifth item of Fig. 1. Isocyanurate linkages are usually more stable than urethane linkages. Model compound studies show no degradation of the trimer of phenyl isocyanate below 270°C [10,11]. Catalysts are usually needed to form the isocyanurate bond. Alkali metals of carboxylic acids, such as potassium acetate, various quaternary ammonium salts, and even potassium or sodium hydroxide, are most commonly used as catalysts for the isocyanurate reaction. However, many others will work as well [12]. 

Guo et al. [70,71,73] recently attempted to hydrogenate NBR in emulsion form using Ru-PCy complexes. However, successful hydrogenation can only be obtained when the emulsion is dissolved in a ketone solvent (2-butanone). A variety of Ru-phosphine complexes have been studied. Crosslinking of the polymer could not be avoided during the reaction. The use of carboxylic acids or first row transition metal salts as additives minimized the gel formation. The reactions under these conditions require a very high catalyst concentration for a desirable rate of hydrogenation. 

From the preceding discussion, it is easily understood that direct polyesterifications between dicarboxylic acids and aliphatic diols (Scheme 2.8, R3 = H) and polymerizations involving aliphatic or aromatic esters, acids, and alcohols (Scheme 2.8, R3 = alkyl group, and Scheme 2.9, R3 = H) are rather slow at room temperature. These reactions must be carried out in the melt at high temperature in the presence of catalysts, usually metal salts, metal oxides, or metal alkoxides. Vacuum is generally applied during the last steps of the reaction in order to eliminate the last traces of reaction by-product (water or low-molar-mass alcohol, diol, or carboxylic acid such as acetic acid) and to shift the reaction toward the... 

Trimerization to isocyanurates (Scheme 4.14) is commonly used as a method for modifying the physical properties of both raw materials and polymeric products. For example, trimerization of aliphatic isocyanates is used to increase monomer functionality and reduce volatility (Section 4.2.2). This is especially important in raw materials for coatings applications where higher functionality is needed for crosslinking and decreased volatility is essential to reduce VOCs. Another application is rigid isocyanurate foams for insulation and structural support (Section 4.1.1) where trimerization is utilized to increase thermal stability and reduce combustibility and smoke formation. Effective trimer catalysts include potassium salts of carboxylic acids and quaternary ammonium salts for aliphatic isocyanates and Mannich bases for aromatic isocyanates. 

The paraffin wax is oxidized by air in a liquid phase process at 110-130°C. Catalysts for this radical reaction are cobalt or manganese salts [54]. The quality of the obtained mixture of homologous carboxylic acids is impaired by numerous byproducts such as aldehydes, ketones, lactones, esters, dicarboxylic acids, and other compounds. These are formed despite a partial conversion of the paraffin and necessitate an expensive workup of the reaction product [50,55]. 

The reaction of step 2 is carried out by heating the reagents with various acid catalysts, such as orthophosphoric acid or its acid salts, bringing the pH down to 2.3-3.2 [4]. The Igepon A type of surfactant is quite susceptible to hydrolysis, particularly on the alkaline side, as is characteristic for most esters of carboxylic acids. It is therefore used most advantageously at a fairly neutral pH, such as combination soap-syndet toilet bars. 

---