Extractants monoamides

Hydrochloric acid [7647-01-0], which is formed as by-product from unreacted chloroacetic acid, is fed into an absorption column. After the addition of acid and alcohol is complete, the mixture is heated at reflux for 6—8 h, whereby the intermediate malonic acid ester monoamide is hydroly2ed to a dialkyl malonate. The pure ester is obtained from the mixture of cmde esters by extraction with ben2ene [71-43-2], toluene [108-88-3], or xylene [1330-20-7]. The organic phase is washed with dilute sodium hydroxide [1310-73-2] to remove small amounts of the monoester. The diester is then separated from solvent by distillation at atmospheric pressure, and the malonic ester obtained by redistillation under vacuum as a colorless Hquid with a minimum assay of 99%. The aqueous phase contains considerable amounts of mineral acid and salts and must be treated before being fed to the waste treatment plant. The process is suitable for both the dimethyl and diethyl esters. The yield based on sodium chloroacetate is 75—85%. Various low molecular mass hydrocarbons, some of them partially chlorinated, are formed as by-products. Although a relatively simple plant is sufficient for the reaction itself, a si2eable investment is required for treatment of the wastewater and exhaust gas. 

A key technology that is imperative to society should have, and be prepared with, alternatives at all times. Thus, different kinds of monodentate extractants have been investigated worldwide. They are monoamides (107-115), dialkylsulfoxides (116-121), and trialkyl (122,123) and tricyclohexyl phosphates (124). 

Rabbe, C., Madic, C., Godard, A. 1998. Molecular modeling study of uranyl nitrate extraction with monoamides I. Quantum chemistry approach. Solvent Extr. Ion Exch. 16 (1) 91-103. 

Several spectroscopic techniques, namely, Ultraviolet-Visible Spectroscopy (UV-Vis), Infrared (IR), Nuclear Magnetic Resonance (NMR), etc., have been used for understanding the mechanism of solvent-extraction processes and identification of extracted species. Berthon et al. reviewed the use of NMR techniques in solvent-extraction studies for monoamides, malonamides, picolinamides, and TBP (116, 117). NMR spectroscopy was used as a tool to identify the structural parameters that control selectivity and efficiency of extraction of metal ions. 13C NMR relaxation-time data were used to determine the distances between the carbon atoms of the monoamide ligands and the actinides centers. The II, 2H, and 13C NMR spectra analysis of the solvent organic phases indicated malonamide dimer formation at low concentrations. However, at higher ligand concentrations, micelle formation was observed. NMR studies were also used to understand nitric acid extraction mechanisms. Before obtaining conformational information from 13C relaxation times, the stoichiometries of the... 

Bhattacharyya, A. Banerjee, S. Mohapatra, P.K. Basu, S. Manchanda, V.K. Extraction of ternary beta-diketonates of uranyl ion using some substituted monoamides, Solvent Extr. Ion Exch. 21 (2003) 687-705. 

The exclusive isolation of uranium at the front-end by an amide extractant (BAMA process using a Branched Alkyl MonoAmide)... 

Tachimori, S., Sasaki, S., Suzuki, S. 2002. Modification of i OIXiA-n-dodccane solvent with a monoamide for high loading of lanthanides(IH) and actinides(IH). Solvent Extraction and Ion Exchange 20(6) 687-699. 

Alkyl-substituted monoamides are known as extractants for the uranyl cation and they could potentially be considered as alternatives to organophosphorus compounds in nuclear fuel reprocessing. In toluene, the uranyl cation forms complexes with two monoamide molecules. These relatively simple molecules were selected for computer-aided design,14 taking into account a lot of synthetic and experimental work that must be done to prove the modeling predictions. 

Tachimori et al. (5) and Sazaki et al. (104) studied the effect of adding a monoamide modifier to a TODGA (0.1 or 0.2 M)-dodecane/Nd(III) extraction system. iV,iV-dihexyloctanamide (DHOA) was used as a representative monoamide modifier. It was shown that adding this modifier suppressed the third phase and that the amount of extracted Nd(III) reached the stoichiometric value. DHOA alone has a very weak extractability for Nd(III), and the explanation given is increased solvent polarity within an outer-sphere organization. 

Y. Sasaki, Y. Sugo, S. Suzuki, and T. Kimura. A method for the determination of extraction capacity and its application to N,N,N, N -tetraalkyl derivatives of diglycol-amide-monoamide/n-dodecane media. Anal. Chim. Acta, 543(1-2) 31—37, 2005. 

Extraction of Other Fission Products. The extraction of lanthanides by monoamides is weak, but some authors have performed tests after irradiation, showing that, for a similar dose (1 MGy), DEu could decrease slightly (from 10 2 to 0.2 x 10-2) (191) or remained stable (194) for 0.5 mol I. amide in n-dodecane, but could increase (from 0.5-0.6 to 4-6) (192) for 0.5 mol L4 amide in benzene. The irradiation seemed to have no influence on Am(III) extraction (191). 

The extraction of Zr increased with the absorbed y-dose (factor of 20 up to 0.7-0.8 MGy for linear amides in n-dodecane (191) and factors of 4-6 up to 0.3-0.6 MGy for shorter amides in benzene) (192). Beyond this threshold, the extraction decreased slightly. This effect is more noticeable with N-methyl amides (192). As for Pu(TV), the first step has been explained by authors by a synergistic extraction due to the presence of carboxylic acids as degradation products (191). Nevertheless, the degradation had a stronger effect on the decontamination factors of U and Pu with respect to Zr(IV) than with TBP (191). Typically, decontamination factors were DEM/Zr = 7 and 12 for, respectively, U(VI) and Pu(IV) with TBP and 5 with the monoamide DHOA at an irradiation dose of 300 MGy (193). 

In the presence of dodecane, as for other extractants like TBP or monoamides, radiolysis was increased (182,199). 

Different studies indicate that diluents can inhibit or sensitize an extractant s radiolysis. For example, in the cases of alkyl phosphates, amide extractants, or crown ethers, aromatic additives act as protectors (39, 84, 88, 90, 199, 254, 298), while saturated hydrocarbons often sensitize the decomposition of the extractant (90, 182, 183, 199, 299). Figure 8.18 illustrates this sensitization effect of n-dodecane on various oxygen-donor ligands (diglycolamide, malonamide, and monoamides) (199). 

Preparation ofS [1] A solution of N-(tert-butyloxy)carbonyliminodiacetic acid (1) (0.349 g, 1.50 mmol) in dimethyl formamide (DMF) (15 ml) was treated with N -(3-dimefhylaminopropyl)-N-ethyl-carbodiimide hydrochloride (EDC) (0.294 g, 1.54 mmol) at 25 °C. The mixture was stirred at 25 °C for 1 h, and then the amine (1 equiv.) was added and the reaction mixture was stirred for 20 h. It was then poured into 10% aqueous HCl (60 mL) and extracted with ethyl acetate (100 mL). The organic phase was washed with 10% HCl (40 mL) and saturated aqueous NaCl (2 x 50 mL), dried (NazSOr), filtered, and concentrated in vacuo to yield the diacid monoamides 2. Each of the diacid monoamides 2 was dissolved in anhydrous DMF (20 mL/mmol) and the solutions obtained were divided into three equal portions in three separate vials. Each solution was then treated with one of the three amines (1 equiv.), diisopropylefhylamine (2 equiv.), and (benzotriazol-l-yloxy)tripyr-rolidinophosphonium hexafluorophosphate (PyBOP) (1 equiv.). Each solution was stirred at 25 °C for 20 h. The respective mixture was then poured into 10% HCl and extracted with ethyl acetate. The organic phase was washed sequentially with 10% HCl, saturated aqueous NaCl, 5% aqueous NaHCOs, and further saturated aqueous NaCl, then dried (Na2SO4), filtered, and concentrated to yield the diamides 3. Each of the diamides 3 was dissolved in 4 N HCl/dioxane (32 mL/mmol) and the respective mixture was stirred at 25 °C for 45 min. The solvent was then removed in vacuo, the residue was dissolved in anhydrous DMF (28 mL/mmol), and the solution obtained was divided into three equal portions, which were placed in three separate vials. Each solution was treated with one of three carboxylic acids (1 equiv.) followed by diisopropylamine (3 equiv.) and PyBOP (1 equiv.) and the mixtures were stirred for 20 h. Each mixture was then poured into 10% HCl and extracted with ethyl acetate. The organic phase was washed sequentially with 10% HCl, saturated aqueous NaCl, 5% aqueous NaHCOs, and further saturated aqueous NaCl, then dried (Na2SO4), filtered, and concentrated in vacuo to yield the final products 5. 

Extraction data for some alkali, alkaUne earth, Ag" and Pb cations with tetrahomodioxa derivatives 45-51 were reported [34—36]. The results showed no metal cation affinity for ester 45 and the monoamides 50 and 51. In the latter case, the presence of intramolecular hydrogen bonding between NH and CO groups decreases the metal ion binding ability. Tertiary amides 46 and 48 are better... 

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