SYNERGISTIC EFFECTS IN SOLVENT-EXTRACTION SYSTEMS BASED ON ALKYLSALICYLIC ACIDS. IV. EXTRACTION OF THE TRIVALENT RARE-EARTH METALS IN THE PRESENCE OF BIFUNCTIONAL C=0, P=0 AND S=0 COMPOUNDS

ABSTRACT

Several bifunctional compounds of different types (diamides, diphosphonates and disulphoxides) were synthesized, and their effect on the extraction of the trivalent rare-earth metals from chloride media by solutions of some alkylsalicylic acids (HA) in xylene was investigated. Appreciable synergistic shifts in the individual pH₅₀ values were observed in most cases, the shifts generally increasing in the order S=0 ≤ C=0 < P=0 for comparable bifunctional compounds containing these donor groups. For compounds with C=0 or P=0 groups, the synergism is greater when the two groups are separated by a one-carbon bridge (-CH₂-) than by a two-carbon bridge (-CH₂-CH₂-), whereas the opposite is true for compounds containing S=0 groups. For a given bifunctional compound, the synergistic shifts were found to increase with increasing steric bulk of the alkylsalicylic acid

The synergistic shifts produced by the addition of a given bifunctional compound generally decrease across the lanthanide series (La to Lu), which suggests that coordination of the neutral ligand is somewhat dependent on steric factors. For the diamides and diphosphonates containing a -CH₂- bridge, the synergistic effects in the extraction of neodymium (and lanthanum) are substantially greater than for their monofunctional analogues, which suggests that these bifunctional compounds may be coordinated to these metals in a bidentate mode. Slope analysis studies and measurements of the solubility of the neodymium-alkylsalicylic acid complex in xylene solutions of the bifunctional ligands (L) are consistent with the formation of complexes of stoichiometry NdA₃L.     

SOLVENT EXTRACTION OF URANIUM( VI) AND THORIUM( IV) FROM NITRATE MEDIA BY CARBOXYLIC ACID AMIDES

ABSTRACT

A series of nineteen N-alkyl carboxylic acid amides (R.CO.NHR') has been prepared, in which the alkyl groups R and R' have been varied in order to introduce different degrees of steric complexity into the compounds. A smaller number of N,N-dialkyl amides (R.CO.NR₂) and non-substituted amides (R.CO.NH₂) has also been prepared for comparison purposes. These amides were characterized by measurement of their boiling points, melting points, refractive indices and densities.|The solvent extraction of uranium(VI) and thorium(IV) from sodium nitrate media by solutions of the amides in toluene was studied. Increasing steric bulk of the alkyl groups R and R' was found to cause a marked decrease in the extraction of thorium, with a much smaller effect on the extraction of uranium, thus considerably enhancing the separation between these metals. Vapour pressure osmometry studies indicate that the N,N-alkyl amides are self-associated in toluene solution, with aggregation numbers up to about 2.5 for 0.6 M solutions at 35°C. In contrast, the N,N-dialkylamides behave as monomers under these conditions. The distribution ratios for the extraction of uranium and thorium show second- and third-order dependences, respectively, on the extractant concentration for both the N-alkyl and N,N-dialkyl amides.     

Synergistic effects in the solvent extraction of some divalent metals by mixtures of versatic 10 acid and pyridinecarboxylate esters

Pyridinecarboxylate esters were found to cause appreciable synergistic shifts in the pH₅₀ values for the extraction of some divalent base metals by solutions of Versatic 10 acid in xylene. For n-octyl 3-pyridinecarboxylate, the synergistic shifts decreased in the order Ni > Co > Cd > Cu ≈ Fe > Mn > Zn, and for the commercial extractant Acorga DS5443A in the order Ni > Cu > Co > Fe > Cd > Mn > Zn. No synergistic effects were observed for divalent lead, calcium and magnesium. On the basis of the pH₅₀ values obtained, several possible practical metal separations are suggested. No loss of metal-loading capacity was found when the organic phases were contacted with 1 M sulphuric acid for prolonged periods at 30°C. The effect of changes in the structure of a series of isomeric octyl pyridinecarboxylates is reported for one of the smaller cations studied (copper), as well as for one of the larger cations (cadmium).     

Oxyethylated secondary amides as soil wetting agents

Polydisperse adducts, RCONR’ (CH₂CH₂O)_xH, with attractive wetting properties were prepared by oxyethylating aliphatic and aromatic secondary amides to calculated x values of 5 to 20. Moderate wetting profiles were observed with adducts where R and R’ contained 15 to 18 carbon atoms and had short ethylene oxide chains. These products, however, contained unreacted amide and/or ester contaminants. Consequently, the products showed high water solubility, fairly flat surface tension curves and average wetting ability. In the transition of adducts derived from aliphatic amides to those from aromatic amides, unreacted amide concentration decreased and ester contaminant increased.     

Catalytic Hydrogenation of Chiral α‐Amino and α‐Hydroxy Esters at Room Temperature with Nishimura Catalyst without Racemization

The hydrogenation of carboxylic acid derivatives at room temperature was investigated. With a mixed Rh/Pt oxide (Nishimura catalyst), low to medium activity was observed for various α‐amino and α‐hydroxy esters. At 100 bar hydrogen pressure and 10% catalysts loading, high yields of the desired amino alcohols and diols were obtained without racemization. The most suitable α‐substituents were NH₂, NHR, and OH, whereas β‐NH₂ were less effective. Usually, aromatic rings were also hydrogenated, but with the free bases of amino acids as substrates, some selectivity was observed. No reaction was found for α‐NR₂, α‐OR, and unfunctionalized esters; acids and amides were also not reduced under these conditions. A working hypothesis for the mode of action of the catalyst is presented.     

The solvent extraction of nickel from acidic solutions using synergistic mixtures containing pyridinecarboxylate esters. Part 2: Systems based on alkylsalicylic acids

The synergistic solvent extraction of nickel and cobalt by pyridinecarboxylate esters (2-, 3- or 4-C₅H₄N.CO.OR) in admixture with 3-bromo- or 3-nitro-derivatives of 5-alkylsalicylic acids was studied. Nickel is extracted more strongly than cobalt in all cases and, for systems containing a given pyridinecarboxylate, the pH₅₀ values (pH values for 50% extraction) of both metals decrease in the order: alkylsalicylic acid > bromo-derivative > nitro-derivative. For systems containing a given salicylic acid, the separation between the pH₅₀ values for nickel and cobalt was found to increase in the order: pyridine 2-ester < 4-ester ≈ 3-ester. The extractability of divalent base metals from sulphate solutions by mixtures of isodecyl 3- or 4-pyridinecarboxylate and 3-bromo- or 3-nitro-5-nonylsalicylic acid in Shellsol K decreases through the series: Cu > Ni > Co ≈ Zn > Ca > Mg. In single-stage batch extraction experiments with a simulated leach liquor containing Ni 2·2, Cu 0·5, Ca 0·4 and Mg 5·0 g dm⁻³ (and smaller amounts of other base metals), adjustment of the equilibrium pH value to between 3·3 and 4·0 with magnesium oxide gave extractions of nickel and copper of 97–100%, with co-extractions of calcium and magnesium of <0·5 and <0·1%, respectively. Amongst the metals present in lower concentrations, manganese (2–5%) and lead (5–10%) were extracted only slightly whereas cobalt (40–80%), zinc (15–65%) and iron (100%) were more strongly extracted.     

Preparation and surface active properties of terminal amide type of alcohol ethoxylates

Three kinds of title amide compounds with different terminal structures (N-unsubstituted amide, N,N-dimethylamide and acylmorpholine) were prepared from alkyl tetra(oxyethylene) monoethers (alkyl: decyl or dodecyl). The cloud points of the N,N-dimethylamides and acylmorpholines were higher than the other corresponding alcohol ethoxylate derivatives previously developed by us, and all these amides inclusive of N-unsubstituted amides had sufficient hydrophilicity. Surface active properties (CMC, γ_CMC and foaming properties) of these amides in pure water and in hard water (1000 ppm of total hardness as CaCO₃) were almost the same and considered excellent as nonionic surfactants. Furthermore, they showed good lime-soap dispersing ability.     

Alkyl Inductive Effects on Molecular Ionization Potentials. XIV. Amides

Correlation of molecular ionization potentials, E_I, with Taft's alkyl inductive substituent constants, σ_I(R), has now been extended to include the amides. It is found that two series of amides, the formamides and acetamides, fall on two separate straight lines in accord with the general equation E_I = E_o + a_I σ_I(R), where E_o is the intercept (E_I for the parent compound), and a_I the slope. Evidence is deduced for the site of electron expulsion and a prediction is made concerning the site of vapor phase protonation of the amides.     

Solvent extraction of the trivalent lanthanides and yttrium by mixtures of 3,5-diisopropylsalicylic acid and neutral organophosphorus compounds

Neutral organophosphorus compounds containing a phosphoryl or thiophosphoryl group were found to cause appreciable synergistic shifts in the pH₅₀ values for the extraction of the trivalent lanthanides and yttrium from chloride media by solutions of 3,5-diisopropylsalicylic acid (DIPSA) in xylene. For the series of compounds with R = n-butyl, the synergistic effect increases in the order (RO)₃PS < (RO)₃PO < (RO)₂RPO < (RO)R₂PO < R₃PO. The synergistic effects are greater for lutetium(III) than for lanthanum(III) and, as a result, the separation across the lanthanide series (pH–pH) increases from only 0·17 pH unit for 0·25 M DIPSA alone to, for example, 0·85 pH unit for a mixture of 0·25 M DIPSA and 0·25 M triisobutylphosphine oxide (TIBPO). Mixtures of DIPSA and TIBPO give somewhat better separation factors between the light and middle lanthanide fractions (β = 3·0) than the commercial Versatic 10 acid (β = 2·6), and separation factors comparable to those of the latter extractant between the heaviest lanthanides (thulium to lutetium).     

Preparation of Some MANNICH Bases from 2-amino- and 2-allylamino-4-methyl-5-acetyl-thiazole

From 2-amino-( 1 a ) and 2-allylamino-4-methyl-5-acetyl thiazole ( 2 a ) and the N-acylated compounds 1 b – f the correspondent MANNICH bases of the type R CO CH₂ CH₂ NR₂ · HCl(NR₂ = morpholino, piperidino, dimethylamino, diethylamino and diisopropylamino) were prepared and characterized as phenylhydrazones. The bromination of these MANNICH compounds gave α-bromo-β-aminoketones.     

Potentiometric studies on the interaction between superoxide dismutase and hyaluronic acid

The formation process of soluble complexes and insoluble aggregates between superoxide dismutase (SOD) and hyaluronic acid (HA) was studied using quasielastic light scattering and turbidimetric titration. The electrostatic binding between them was investigated in detail through potentiometric titration and turbidimetric titration carried out from high to low pH. Turbidimetric titration was used to determine the specific pH values at which soluble complex formation was initiated (pH_c) and phase separation occurred (pH_?). An increase of the ionic strength causes a decrease of pH_c and pH_?. With the increase of HA concentrations, pH_? increases but pH_c does not vary. The formed “salt bridges” between (SOD) and ? COO^? (HA) result in the formation of stable SOD‐HA complexes and even aggregates. The necessary condition of electrostatic binding was also given for protein‐acidic polyelectrolyte systems. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

SOLVENT EXTRACTION OF TRIVALENT LANTHANIDES AND YTTRIUM FROM NITRATE MEDIA BY DIALKYL SULPHOXIDES

The solvent extraction of the trivalent rare-earth metals (the lanthanides and yttrium, Ln³⁺) from nitrate media by xylene solutions of some dialkyl sulphoxides (R₂SO, where R=alkyl) was studied. The salting-out effect of added metal nitrate (5.00 M) increases in the order: NH₄NO₃>NaNO₃>LiNO₃. Extraction is independent of pH in the range from 2 up to at least 4, but decreases gradually below pH 2 due to the competing extraction of nitric acid.

Vapour-pressure osmometry data indicate that the dialkyl sulphoxides are not appreciably self-associated under the conditions studied (0.10 to 0.60M in xylene or toluene solutions at 30°C), which permits the use of organic-phase concentration terms (in place of activities) in the slope-analysis studies. The distribution ratios for the extraction of yttrium, gadolinium and lutetium show a third-order dependence on the concentration of the sulphoxide in the organic phase, with a slightly higher dependence (3.3) for lanthanum. In addition, the mole ratio of nitrate to metal in the loaded organic phase is close to 3, which suggests that the stoichiometry of the extracted complexes is Ln(NO₃)₃(R₂SO)₃.

Increasing the steric bulk of the substituent alkyl groups (R) in the sulphoxides causes a marked decrease in metal extraction, and a reasonable correlation exists between the extraction of a given metal and the sum of the steric parameters of the alkyl groups in each of the sulphoxides used. In traversing the lanthanide series, the extraction increases in the interval La to Sm, and decreases thereafter to the end of the series. The behaviour of yttrium most closely resembles that of thulium or ytterbium.     

Homogeneous Catalytic Cleavage of Saturated Carbon-Nitrogen Bonds

An evaluation of the catalytic reactivity of [CPD (CO)₂RuH]₂ (1) and (CPD)(CO)₃Ru (2) (where CPD = tetraphenylcyclopentadienone) with amines suggests that these complexes catalyze C-N bond cleavage by activating C-H bonds alpha to the nitrogen atom of tertiary, secondary and primary amines at ca. 140° C. When two different amines are used, transalkylation takes place. With secondary and primary amines, ammonia and tertiary amines are formed. A series of amine complexes (CPD)(CO)₂Ru.NR₃ (R = alkyl/H) was isolated from stoichiometric reactions of 1 or 2 with primary and secondary amines. It was found that tertiary amines do not generate complexes of the above type but rather unexpectedly give secondary amine complexes by cleavage of an alkyl group. The only isolatable tertiary amine complex is the moderately stable (CPD)(CO)₂RuNMe₃. All amine complexes were characterized by spectral and elemental analyses. Catalytic aspects of C-N bond cleavage were studied. Complexes (1) and (2) were found to react with primary, secondary and tertiary amines to generate imminium or eneamine species which subsequently undergo hydrolysis with water. This is in contrast to the Ru carbene mechanism previously proposed for cluster catalyzed C-N bond activation and cleavage. The two reactions are compared with respect to D for H exchange (with D₂O), water requirement and production of trace products during catalysis. A primary alcohol was found to substitute alkyl groups of a tertiary amine under the catalytic action of 1. A catalytic reaction cycle is proposed.     

Nonionic surfactant amides as soil wetting agents

Isomeric hydroxyethyl tertiary amides, RCONR′CH₂CH₂OH, where R and R′ are 7- 8 carbon linear or branched aliphatic groups, were oxyethylated to form polydisperse adducts containing 5- 20 moles of ethylene oxide. The adducts RCONR′(E.O.)_xH were free of unreacted amide and contained minimum ester contaminant where R and R′ were branched. Ester content of the adducts does not change with time, but the monomer does revert to amide on standing. All series of adducts showed good wetting at intermediate chain lengths but instantaneous wetting only at short chain lengths where both R and R′ were branched. Good water solubility occurred at the intermediate chain length while maximum surface activity was found for short chain lengths corresponding to a hydrophile- lipophile balance of ~9. All adduct series were excellent wetting agents for cotton skeins and a burned over sandy loam. For this soil the adducts effectively promote wetting at 0.01% level.     

SYNERGISM IN THE EXTRACTION OF ZINC(II)AND CADMIUM(II) WITH SOME LOWER FATTY ACIDS IN THE PRESENCE OF AMINES AND THEIR SEPARATIONS∗

Abstract

Synergism in the extraction of Zn(Il) and Cd(II)with chloroform solution of propionic, butyric and valeric acids in the presence of n-butylamine, dibutylamine, tributylamine, β-picoline, pyridine and quinoline is reported The effect of various parameters affecting extractions has been investigated The compositions of synergistic adduct extracted into the organic phase have been proposed on the basis of slope analysis method. In general the species have been represented as MA2.2HA.B (aliphatic amine system and MA₂.2HA.2B (heterocyclic amine system), where M = zn(Il)/CdII), HA = acid and B = amine. On the basis of extraction constant (K_ex) values the relative effectiveness of different amines as synergists has been compared. Based on the extraction data some separations of metal ions have also been reported with fairly high separation factor (β).     

SYNERGISTIC EXTRACTION OF LANTHANIDES(III) BY TRIOCTYLMETHYLAMMONIUM NITRATE AND TRIBUTYL PHOSPHATE

ABSTRACT

The synergistic action of tributyl phosphate in the extraction of La(III), Pr(III)Nd(III), Sm(III), Eu(III), Gd(III), Dy(III), Ho(III), Er(III)and Y(III) with trioc-tylmethylammonium nitrate was studied. The synergistic effect is diluent dependent. It is pronounced with a mixed dodecane/xylene diluent, and is weak with mixed heptane/xylene and hexane/xylene diluents as well as with pure xylene diluent. Two or three synergistic complexes are formed simultaneously in the organic phase. Their composition is (A₊)(Ln(N0₃)) ₄),.2B~), (A₊))(Ln(N0₃))J.3B"), and (A₊)) ₂) (Ln(N0₃)) ₅).BJ-) (Ln is a lanthanide(IM), A+ is a trioc-tylmethylammonium cation and B is a tributyl phosphate molecule). The stability of the synergistic complexes generally decreases with increasing atomic number of the lanthanides(III). The synergism enhaces the efficiency of the lanthanide(III) extraction with trioctylmethylammonium nitrate, but deteriorates its selectivity. The separation factors for the Pr(III)-Nd(III) and Eu(III)-Gd(III) pairs are gradually suppressed at increasing concentration of tributyl phosphate.     

Potassium Phosphate‐Catalyzed Chemoselective Reduction of α‐Keto Amides: Route to Synthesize Passerini Adducts and 3‐Phenyloxindoles

A chemoselective reduction of α‐keto amides to biologically important α‐hydroxy amides (mandelamides) by polymethylhydrosiloxane (PMHS) using 5 mol% potassium phosphate (K₃PO₄) as catalyst has been developed. This transition metal‐free protocol discloses excellent chemoselectivity for the ketone reduction of α‐keto amides in the presence of other reducible functionalities like ketone, nitro, halides, nitrile and amide. Also, the chemoselectively reduced α‐hydroxy amide has been derivatized to isocyanide‐free Passerini adducts. The N‐alkyl‐α‐hydroxy amides have been successfully converted to 3‐phenyloxindole derivatives by treatment with methanesulfonyl cholride and triethylamine.

     

Aluminium bromide catalysed transalkylations of a Texas lignite coal

Texas lignite coal was treated at a variety of reaction times and temperatures with water-activated AlBr₃ in the presence of either m-xylene or diphenyl ether. Reactions with m-xylene resulted in increases in coal weights, probably due to incorporation of xylene into the coal structure, whereas reactions with diphenyl ether resulted in weight losses in the treated coal. The solubility in pyridine of the coal recovered from these reactions was increased significantly, reaching a maximum of 50% in one reaction with diphenyl ether. Suggestions are made for processes that may explain both the weight increases and the greater pyridine solubility. Support for the occurrence of transalkylation of alkyl groups from lignite to diphenyl ether was provided by g.c.-m.s. analysis of an ether extract in which diphenyl ether molecules substituted with C₁–C₁₃ alkyl groups could be identified. Also of interest was the observation of the compound phenoxathin among the products of transalkylation.     

Screening for Amidases: Isolation and Characterization of a Novel D‐Amidase from Variovorax paradoxus

Using racemic tert‐leucine amide as sole nitrogen source in minimal medium, 162 strains were isolated by enrichment techniques and shown to contain amidase activity. Among these isolates three D ‐amidase producers were found and identified as Variovorax paradoxus (two strains) and Klebsiella spec. The D ‐amidase from Variovorax paradoxus was purified to homogeneity by three chromatographic steps. With dl ‐Tle‐amide as substrate Michaelis Menten kinetics were observed with a K_M of 0.74 mM, a K_I of 640 mM and a V_max of 1.4 U/mg. The amidase has a broad pH‐optimum between 7 and 9.5 and a temperature optimum at 47–49 °C. The amidase hydrolyzed amino acid amides as well as carboxamides and 2‐hydroxy acid amides. The stereoselectivity of the reaction was variable, however. Hydrolyzing dl ‐Tle‐amide the enantiomeric ratio E was >200 resulting in D ‐Tle with an ee of >99% and up to 47% conversion. Similar results were obtained with dl ‐Leu‐amide and dl ‐Val‐amide while dl ‐Phe‐amide was hydrolyzed with an enantiomeric ratio E of only 5.