Ammonium acetate phosphonium salts

Phase-transfer catalysts are used to facilitate reactions between reagents that are in two different phases (e.g., 1-bromooctane in toluene with aqueous potassium iodide to form 1-iodooctane). They are usually quaternary ammonium or phosphonium salts or crown ethers. They can complicate the workup of the reaction and may be difficult to recover for reuse. When they are insoluble polymeric ones, workup and recycle can be done by simple filtration.192 The process is called triphase catalysis. In favorable cases, their activity can be comparable with that of their lower molecular weight analogues. They are often based on cross-linked polystyrene, for which spacers between the aromatic ring and the quaternary onium salt can increase activity two- to fourfold. Copolymerization of 4-vinylben-zyl chloride with styrene or N, N- d i m e Ihy I a c ry I a m i d e, followed by treatment with tri-/ -butylphosphine produced catalysts that were used in the reaction of benzyl chloride with solid potassium acetate (5.43).193... 

Besides this certainiy most important method of end group stabiiization of poiyoxy-methyiene with acetic anhydride, other compounds, such as aiiphatic and aromatic anhydrides or carbon acid imide have also been used, some in the presence of acidic catalysts such as Lewis acids or sulfonic acids. In addition to alkali acetates and tertiary amines as basic catalysts, the following are also mentioned polyamides, polypyrrolidones, or quaternary ammonium and phosphonium salts. 

In the presence of 18-crown-6 the degree of conversion increases with increased solvent polarity, best results being obtained in DMF (Table 1) as expected, the influence of temperature is also quite noticeable. Table 1 shows that the nature of the catalyst and the type of phase transfer reaction, solid-liquid or liquid-liquid, are very important factors. Short-chain tetraalkyl ammonium salts (methyl, ethyl or propyl) have no catalytic activity, while tetrabutyl ammonium or phosphonium salts have good activities several other phase transfer catalysts were also included in this study but will not be reviewed here. Reactions with aqueous solutions of potassium acetate (Table 2) confirm that best results are obtained when a concentrated solution of the salt is used. The scale of catalytic activity for these liquid-liquid reactions is the following ... 

Separation science focuses on room temperature ionic liquids (RTlLs), salts that are liquid at ambient temperature. They have been studied as extracting solvents, stationary and mobile phases, mobile phase additives, and other uses. Common RTILs consist of a bulky nitrogen- or phosphorus-containing organic cation (pyridinium or pyrrolidinium, alkyl-imidazolium, ammonium or phosphonium) and a variety of organic and inorganic anions (triflate, dicyanamide, trifluoroacetate, acetate trifluo-romethylsulfate, nitrate, perchlorate, bromide, chloride, chloroaluminate, tetrafluo-roborate, hexafluorophosphate). 

Solid-Liquid Phase Transfer.—Very few examples are known in onium ion chemistry where the anion to be phase transferred is part of a solid phase rather than in aqueous solution. This contrasts with the situation in crown ether chemistry, as will be discussed later in this review. A useful method, which is cheaper than alternatives, for the generation of dichlorocarbene in neutral conditions involves warming solid sodium trichloroacetate in chloroform, in the presence of quaternary salts. Formaldehyde acetals (25) can be synthesized in good yields by the action of solid KOH on alcohols or phenols dissolved in methylene dibromide containing a quaternary ammonium ion, and a phosphonium salt catalyses the alkylation of solid potassium phthalimide in toluene. Solid-liquid phase transfer mediated by polyamines has been reported. ... 

Other companies (e.g. Hoechst, now Celanese) have developed a slightly different process in which the water content is low in order to save CO feedstock [1], In the absence of water it turned out that the catalyst precipitates. Also, the regeneration of ihodium(III) is much slower. The formation of the trivalent rhodium species is also slower because the HI content is much lower when the water concentration is low. The water content is kept low by adding part of the methanol in the form of methyl acetate. Indeed, the shift reaction is now suppressed. Stabilisation of the rhodium species and lowering of the HI content can be achieved by the addition of iodide salts (Li, ammonium, phosphonium, etc). Later, we will see that this is also important in the acetic anhydride process. High reaction rates and low catalyst usage can be achieved at low reactor water concentration by the introduction of tertiary phosphine oxide additives [1]. 

Jn a potentially far reaching application for melt catalysis by the transition metals, we at Texaco have demonstrated the synthesis of a range of commodity chemicals and fuels directly from CO/H2 via the use of ruthenium-containing molten salt catalysis. Products include ethylene glycol, Ci-C4 alcohols, acetic acid, acetate esters, C2+ olefins and vicinal glycol esters. In its simplest form, this new class of melt catalyst comprises one or more ruthenium sources, e.g. ruthenium carbonyls, oxides, complexes, etc. dispersed in a low-melting (m.p. <150 C) quaternary phosphonium or ammonium salt (e.g. tetrabutylphos-phonium bromide). The key components are selected such that ... 

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