Molten ammonium salts

In some cases, the Q ions have such a low solubility in water that virtually all remain in the organic phase. ° In such cases, the exchange of ions (equilibrium 3) takes place across the interface. Still another mechanism the interfacial mechanism) can operate where OH extracts a proton from an organic substrate. In this mechanism, the OH ions remain in the aqueous phase and the substrate in the organic phase the deprotonation takes place at the interface. Thermal stability of the quaternary ammonium salt is a problem, limiting the use of some catalysts. The trialkylacyl ammonium halide 95 is thermally stable, however, even at high reaction temperatures." The use of molten quaternary ammonium salts as ionic reaction media for substitution reactions has also been reported. " " ... 

There is nothing unusual about the acidic behavior of ammonium salts. In fact, any protonated amine can function as a proton donor. Because of this, many amine salts have been used as acids in synthetic reactions. If the chlorides are used, the amine salts are known as amine hydrochlorides. One of the earliest amine hydrochlorides studied with regard to its behavior as an acid is pyridine hydrochloride (pyridinium chloride), C5H5NH+C1. In the molten state, this compound undergoes many reactions of the type just shown. 

When sodium chloride is dissolved in water at ordinary temperatures, it is practically completely dissociated into sodium and chloride ions which, under the action of an external field, move in opposite directions and independently of each other subject to coulombic interactions. If, however, sodium chloride is dissolved in a solvent of lower dielectric constant, and if the solution is sufficiently dilute, there is an equilibrium between ions and a coulombic compound of the two ions which are commonly termed 4 ion pairs. This equilibrium conforms to the law of mass action when the interaction of the ions with the surrounding ion atmosphere is taken into account. In solvents of very low dielectric constant, such as the hydrocarbons, sodium chloride is not soluble however, many quaternary ammonium salts are quite soluble, and their conductance has been measured. Here at very low concentrations, there also is an equilibrium between ions and ion pairs which conforms to the law of mass action but at higher concentration, in the neighborhood of 1 X 10 W, or below, a minimum occurs in the conductance. Thereafter, it may be shown that the conductance increases continuously up to the molten electrolyte, provided that a suitable electrolyte and solvent are employed which are miscible above the melting point of the electrolyte. 

Reaetions no. 6 and no. 7 in Table 5-15 demonstrate that with molten quaternary ammonium salts as solvents, where deaetivation by anion solvation is absent, the halide ions show the same nueleophilie order as in dipolar non-HBD solvents [283, 284], This is in aeeordanee with the theory of protie/dipolar non-HBD medium effeets on X nueleophilieity [6j. It has been suggested that fused-salt experiments should provide a good model for the determination of intrinsie relative nueleophilieities of anions towards saturated earbon atoms [284],... 

Thionyl chloride is frequently the reagent of choice for the dehydration of higher-molecular-weight amides, since the secondary products are gaseous and the nitrile is more readily purified. Oftentimes, the higher fatty acids are converted to the nitriles in a single operation via the intermediate ammonium salts and amides. For this purpose, dry ammonia gas is passed into the molten acids at 290-300° the yields of nitriles are excellent (80-85%). A small amount of 85% phosphoric acid appreciably reduces the reaction time. Another procedure consists in passing the acid vapors mixed with ammonia over silica gel at 500°. This technique... 

Aryl bromides as well as aryl chlorides show increased reactivity in the Mizo-roki-Heck vinylation (eq. (3)) with various olefins when the reaction is performed in molten ammonium or phosphonium salts [28] (see also Section 3.1.6). Many common catalysts, including ligand-free Pd salts, show a substantial inerease in activity and thermal stability. 

The alkali, alkaline earth and ammonium nitrates all melt before decomposing. The homogeneous decomposition of the molten sodium salt proceeds [57] through intermediate formation of the nitrite. Johnson and Forten [52] concluded from studies of the radiation-induced decompositions of (Na, K, Cs and Pb ) nitrates that the mechanisms are complex and depend on the relative importance of the reactions ... 

The steam produced is removed from the molten ammonium nitrate (m.p. 170°C) via the vortex finder of a cyclone separator, and the 99+% molten salt proceeds to either a cooled stainless steel belt to produce a flaked product (Fig. 11.10), or to a 30-m-high prilling tower where droplets of melt fall through a countercurrent dry air stream to produce shot-sized prills (beads) of ammonium nitrate. A hot concentrated solution of ammonium nitrate is explosively sensitized by traces of acid so care is taken to add sufficient ammonia to the wet melt to keep the pH above about 5. 

In an alternative approach, ammonia was bubbled through molten ammonium acetate containing 2-formamidoacetophenone at 160°C to give an excellent yield of 4-methylquinazoline.98 In a ring transformation, ammonia was used to convert 2-alkyl-4-phenyl-3,l-benzoxazinium (89) salts to 2-alkyl-4-phenylquinazolines."... 

Biguanide is prepared by the ammoniation of dicyanodi-amide (cyanoguanidine). The reaction is accomplished by ammonium salts in the molten condition or by ammonia under pressure. In the following preparation, which is essentially that of Bamberger and Dieckmann, ammonium chloride is used as the ammoniating agent. The influence of reaction conditions on this type of reaction has been studied in some detail. ... 

Synonyms Phosphatidic acid, ammonium salt Definition Ammonium salts of phosphatidic acids derived from edible fats and oils Properties Unctuous semisolid sol. in fats partly sol. in ethanol insol. in water Uses Emulsifier in foods, dairy-based beverages vise, control agent for molten chocolate, substitute for soya lecithin in cocoa, chocolate prods., confectionery Features Flavor-free Ammonium phosphite CAS 51503-61-8... 

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 ... 

Active substances should have large solubility, stability and can decompose into stable active compounds following calcining. Impregnating solution generally is made from nitrate, chloride, acetate, ammonium salt or molten salt such as molten nitrate. 

John Wilkes insightful review of the history of ionic liquids up to 2002, he showed that these neoteric compounds are not so new after all. In fact, their history dates back to the nineteenth century, where probably the first documented case of an ionic liquid was recorded when a red oil was observed to form during a Friedel-Crafts reaction. Work in the early twentieth century demonstrated that simple ammonium salts could be liquids below room temperature. For example, ethylammonium nitrate has a melting point of 12°C. Even though ionic liquids have been known for many years, it took a long time for them to become popular in the research community. As shown in Figure 1, very little publication activity on ionic liquids existed prior to 2000. From 1980 to 1989, one finds from a Web of Science search that only 35 articles appeared that used the term ionic liquid. Perhaps if we expand the search a bit and include those studies that used the term molten salt to mean ionic liquid as defined here, we may have retrieved a few more examples. Still, at one time in the recent past it was possible for a person to read every article published on the topic and still have time to eat, sleep, and carry out his or her own research. Everybody working in the field knew one another, and each of those researchers was familiar with the complete literature. What a difference a few years make ... 

The ammonium nitrate solution is heated to evaporate off the water and melt the solid. The molten solid is then sprayed into a tower with air blown into it. This solidifies the ammonium nitrate into pellets, which makes it convenient for farmers to spread from tractors (Figure 13.6). Ammonium sulfate, (NH j SO, and ammonium phosphate, (NH jjPO, are other ammonium salts used in fertilisers. 

---