Alkylammonium extractants

However, similar problems can also occur with the alkylammonium extractants, especially as the pH of the solution must be sufficiently high to produce an adequate concentration of the amino acid anions, i.e., more than two units above the pK of the amino acid. Thus, coextraction of hydroxyl ions competes with the amino acid anions and in addition lowers the pH of the aqueous phase and reduces the concentration of amino acid anions. To avoid such problems, a large buffer capacity is required in the aqueous phase with the buffer chosen to minimize coextraction of anions. 

Kertes, A.S., lUPAC Chemical Data Series Critical Evaluation of Some Equilibrium Constants Involving Alkylammonium Extractants, Pergamon Press, Oxford, 1977. 

Catalyst Cation. The logarithms of extraction constants for symmetrical tetra- -alkylammonium salts (log rise by ca 0.54 per added C atom. Although absolute numerical values for extraction coefficients are vastly different in various solvents and for various anions, this relation holds as a first approximation for most solvent—water combinations tested and for many anions. It is important to note, however, that the lipophilicity of phenyl and benzyl groups carrying ammonium salts is much lower than the number of C atoms might suggest. Benzyl is extracted between / -propyl and -butyl. The extraction constants of tetra- -butylammonium salts are about 140 times larger than the constants for tetra- -propylammonium salts of the same anion in the same solvent—water system. 

Certain long-chain alkylammonium salts, notably tricaprylmethyl-ammonium chloride (Aliquat 336-S) and tri-Ao-octylamine hydrochloride (TIOA) are liquids, sometimes referred to as liquid anion exchangers, which can form extractable ion pairs or aggregates with anionic metal complexes in the... 

Pertechnetate in neutral and alkaline media can be extracted into solutions of tetra-alkylammonium iodides in benzene or chloroform. With tetra-n-heptylammo-nium iodide (7.5 x 10 M) in benzene distribution coefficients up to 18 can be obtained . A solution of fV-benzoyl-iV-phenylhydroxylamine (10 M) in chloroform can be used to extract pertechnetate from perchloric acid solution with a distribution coefficient of more than 200, if the concentration of HCIO is higher than 6 M The distribution of TcO between solutions of trilauryl-ammonium nitrate in o-xylene and aqueous solutions of nitrate has been measured. In 1 M (H, Li) NOj and 0.015 M trilaurylammonium nitrate the overall equilibrium constant has been found to be log K = 2.20 at 25 °C. The experiments support an ion exchange reaction . Pertechnetate can also be extracted with rhodamine-B hydrochloride into organic solvents. The extraction coefficient of Tc (VII) between nitrobenzene containing 0.005 %of rhodamine-B hydrochloride and aqueous alcoholic " Tc solution containing 0.0025 % of the hydrochloride, amounts to more than 5x10 at pH 4.7 . 

It is interesting to observe that alkylammonium salts, alkylarylsnlfonic acids, hydroxyoximes, aUcylphosphoric acids, and alkylhydroxamic acids, as well as nentral extractants such as crown ethers and tributyl phosphate, all form water-organic interfaces saturated with extractant molecules when their bulk organic concentration is larger than 10" M. 

Abstract—The nature of the product of the reaction between an aminated silane and carbon dioxide was re-examined with the aid of simple model compounds, several amines, and several aminosilanes. Since the reaction products previously proposed include the amine bicarbonate and a carbamate derived from the amine, ammonium bicarbonate and ammonium carbamate were studied as models for the anions. Carbon dioxide adducts of neat model amines were prepared and studied. Results from a variety of techniques are summarized. Among the most useful was Fourier transform infrared (FTIR) spectroscopy of fluorolube mulls. FTIR spectra were distinctive and assignments characteristic of the two species were extracted from the spectral data. Comparisons of these assignments with the products of the reaction between carbon dioxide and various amines were made. The results indicate that alkylammonium carbamates are the principal product. Nuclear magnetic resonance (NMR) spectra in D20 indicated much dissociation and were not helpful in defining the products. 

Nesper and co-workers [219, 248] synthesized nanotubules of alkylammonium intercalated VO by hydrothermal means. The vanadium alkoxide precursor was hydrolyzed in the presence of hexadecylamine and the hydrolysis product (lamellar structured composite of the surfactant and the vanadium oxide) yielded VO, nanotubes along with the intercalated amine under hydrothermal conditions (Figure 8.27(a) and (b)). The interesting feature of this vanadium oxide nanotube is the presence of vanadium in the mixed valent state, thereby rendering it redox-active. The template could not be removed by calcination as the structural stability was lost above 250 °C. Nevertheless, it was possible to partially extract the surfactant under mildly acidic conditions. These workers have later shown that the alkylamine intercalated in the intertubular space could be exchanged with other alkylamines of varying chain lengths as well as a,co-diamines [248]. The distance... 

A large variety of ILs of high purity with water content below lOOppm and halide content below lOppm are now available commercially. These include numerous iV-alkylpyridinium, 7V,7V -dialkylimidazolium, alkylammonium and alkylphosphonium salts, covalent hydrophobic ILs (e.g. l,2-dimethyl-3-propyliniidazolium bis(trifluoromethylsulfonyl)imide, task-specific ILs, Bronsted acidic ILs (e.g. 3-[triphenylphosphonio]propane-l-sulfonic acid tosylate), nitrile-fiinction sed ILs, perfluorinated ILs (e.g. tetrabutylammonium nonafluorobutane sulfonate, BASF Basionics (e.g. 1,2,3-trimethylimidazolium methyl sulfate), and TOMATS for heavy metal extraction (e.g. methyltrioctylammonium thiosalicylate)... 

Diborane finds such wide use in steroid chemistry that a new and very simple procedure for its preparation is welcomed. Tetra-alkylammonium borohydrides, which are readily extracted from an aqueous solution of Na BH and R4N -HSOT into CH2CI2, are used in the dried CH2CI2 solution addition of an alkyl halide (e.g. Mel) generates diborane in situ, and allows all the usual reactions of reduction or hydroboronation to be carried out conveniently and in high yields. 

In the case of the extraction of anionic complexes by alkylammonium reagents according to equation (140), Dm is given by equation (141) in which ML/ is the only extracted species and various ML/"" complexes are present in the aqueous phase /Com is the equilibrium constant for reaction (140). Equation (141) indicates that, as [L ] increases from 0, a greater proportion of M will be in the form of so that Dm should increase. However, provided x is less... 

Calculations with the water uptake measurements illustrated in Fig. 13 have shown that the stoichiometric ratio between the mixed extractant and water is 1 1, so the first step of the sequence of reactions may be assumed to be the formation of alkylammonium 2-ethylhexanoate monohydrate ... 

T. Sato, M. Yamamoto, and H. Watanabe, The extraction of divalent manganese, cobalt, nickel, copper, zinc, cadmium and mercury from aqueous solutions by long-chain alkylammonium carboxylates. Proceedings of Int. Solv. Extr. Conf., 1980, paper 80-178. 

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