Extraction quaternary ammonium salts

A typical composition of the catholyte is adiponitrile, 15 wt % acrylonitrile, 15 wt % quaternary ammonium salt, 39 wt % water, 29 wt % and by-products, 2 wt %. Such a solution is extracted with acrylonitrile and water, which separates the organics from the salt that can be returned to the cell. 

Basic Extractants. Only long-chain quaternary ammonium salts, R3NCH3 X , ia which R represents Cg—0 2 groups and X nitrate or thiocyanate, are effectively used for REE separations (see Quaternary ammonium compounds). The extractant reacts with REE according to an anion-exchange reaction ... 

The quaternary ammonium salts (QAS) are widely used as ionofores of ion-selective electrodes and extractants of metals halogenic anion complexes. The influence of the QASes nature with various methyl groups contents on the cadmium extraction from bromide media has been investigated. 

ANION-EXCHANGE EXTRACTION OF ZINC THIOCYANATE COMPLEXES BY NON-SYMMETRIC QUATERNARY AMMONIUM SALTS... 

High tendency of ZnfSCN) ion to extraction into organic phase is widely used for zinc determination by extraction photometry method. Recently it was shown that when single-chai ged anions ai e exchanged for double-chai ged ones, the selectivity of this process depends on the number of methyl substitutients in quaternary ammonium salt (QAS) cation. 

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. " " ... 

Korenaga et al. [26] have described an extraction procedure for the spectrophotometric determination of trace amounts of aluminium in seawater with pyrocatechol violet. The extraction of ion-associate between the alu-minium/pyrocatechol violet complex and the quaternary ammonium salt,... 

Increasing the hydrophobicity of quaternary ammonium salts increases the apparent extraction constants for the ion pair and therefore leads to a higher catalytic activity (Brandstrom, 1977). The same phenomenon has been observed by Cinquini and Tundo (1976) for crown ether catalysis (Table 35). The catalytic activity of 18-crown-6 [3] and alkyl-substituted derivatives [117]—[ 119] in the reaction of n-CgH17Br with aqueous KI follows the order [117], [118] > [119] s> [3]. The alkyl-substituted [2.2]-cryptand derivatives are also much more efficient than the parent compound [86]. Increasing the hydrophobicity of [2.2.2]-cryptand (Cinquini et al., 1975) and even of polypode ligands (Fornasier et al., 1976) leads to higher catalytic activity. The tetradecyl-substituted compounds show the reactivity sequence [2.2.2]-cryptand at 18-crown-6 > [2.2]-cryptand on the reactivity scale that can be distilled from Table 35. 

In the main, the original extractive alkylation procedures of the late 1960s, which used stoichiometric amounts of the quaternary ammonium salt, have now been superseded by solid-liquid phase-transfer catalytic processes [e.g. 9-13]. Combined soliddiquid phase-transfer catalysis and microwave irradiation [e.g. 14-17], or ultrasound [13], reduces reaction times while retaining the high yields. Polymer-supported catalysts have also been used [e.g. 18] and it has been noted that not only are such reactions slower but the order in which the reagents are added is important in order to promote diffusion into the polymer. 

The first examples of the application of phase-transfer catalysis (PTC) were described by Jarrousse in 1951 (1), but it was not until 1965 that Makosza developed many fundamental aspects of this technology (2,3). Starks characterized the mechanism and coined a name for it (4,5), whilst Brandstrom studied the use of stoichiometric amounts of quaternary ammonium salts in aprotic solvents, "ion-pair extraction" (6). In the meantime Pedersen and Lehn discovered crown-ethers (7-9) and cryptands (10,11), respectively. 

Studenov and Beriidge introduced a series of potential F-labeled extractable MBF tracers in the year 2001 that were accessible via reliable 1-2-step radiosynthesis sequences. Five F-labeled amines and four quaternary ammonium salts were obtained by nucleophilic substitution either at aliphatic precursors or at aromatic compounds [71]. Figure 10 summarizes the synthesis of mentioned compounds. 

Schugerl 115] has recently furnished a detail analysis of the reactive extraction of penicdlin-G and V and precursors like phenyl and phenoxy acetic acids. Thirty different amines have been studied for reactive extraction of penicillins 116] in various solvents such as butyl acetate, chloroform, di-isopropyl ether, kerosene, dioctyl ether, etc. Tertiary amines in n-butyl acetate were found to be advantageous because of their low reactivity with solvent but the distribution coefficients of their complexes are significantly lower than those of secondary amines. While using quaternary ammonium salts for ion-exchange extraction, re-extraction is difficult and very large amounts of anion (e.g.. Cl ) are needed to recover penicillins. The basic relationship for distribution coefficient and extraction kinetics have now been fairly developed for amine-penicillin systems. 

To the precipitate was added dichloromethane, and then the combined organic extracts were filtered and concentrated in vacuo to afford the corresponding azacrown ether-type quaternary ammonium salt (0.27 g, 85%) as a light brown crystalline solid. The purity of the cmde product is high enough to be used in the catalysis experiments, m.p. 118-119 °C [a]p 71 (c= 1.0, CHCI3). 

From this ranking, quaternary ammonium acetates, chlorides, nitrates, and bromides are apparently more soluble in organic solvents such as aqueous /-butyl alcohol than are the corresponding quaternary ammonium hydroxides. Thus these quaternary ammonium salts would be readily extracted into the organic phase. In addition, a high concentration of... 

Although rhodium has probably not been recovered commercially by solvent extraction, it can be extracted by quaternary ammonium salts under certain conditions,250 the anion [Rh2Cl9]3-having been identified in extracts from aqueous phases containing the species [Rh(H20)Cl5]2-. 

The prevailing extraction-chromatographic approach for 99Tc separation is the use of Aliquat 336, a liquid quaternary ammonium salt (see Scheme 9.1), as an anion... 

TEVA-Resin is an extraction-chromatographic material based on Aliquat 336, which is a liquid quaternary ammonium salt, as described previously in connection with "Tc separations.30 It acts as a strongly basic anion-exchange material, retaining tetravalent actinides from 2-4 M HN03 solutions as anionic nitrato complexes (see Figure 9.11). Am(III), Np(V), and U(VI) are much less retained. The extraction... 

A vigorously stirred suspension of 0.2 to 1 mole of sodium amide in 200 ml of xylene, in which were dissolved 0.1 mole of a,a-diphenyl-7-hexamethyleneimino butyronitrile was boiled for 12 hours. Thereupon the excess of sodium amide was decomposed with water and the xylene layer was separated, washed with water and extracted with hydrochloric acid. This acidic extract was made strongly alkaline with concentrated lye and the separated base was extracted with ether. After drying, the ether was evaporated and the l,l-diphenyl-3-hexamethyleneimino propane distilled in vacuo. The boiling point was 170-174°C/1 mm, the refractive index nD20 = 1.56 36, and the density d420 = 1.009. From the oil obtained several acid additions and quaternary ammonium salts can be obtained by reaction with acids containing a non-toxic anion or esters thereof. The hydrochloric acid salt, for instance, melts at 189-192°C, the methiodide at 174-177°C under decomposition. 

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