Solvent extraction of scandium from malonic acid with high molecular-weight amines

Scandium is quantitatively extracted with 4% Amberlite LA-1 or Amberlite LA-2 in xylene at pH 2.5-5.5 from 0.1M malonic acid. Scandium is stripped from the organic phase with 0.5M hydrochloric acid and determined spectrophotometrically at 525 nm, as its complex with Alizarin Red S. Primene JM-T, tri-iso-octylamine, tributylamine and tribenzylamine have also been studied as extractants, but found to be unsatisfactory for various reasons. Xylene, toluene, benzene, chloroform, carbon tetrachloride, hexane, cyclohexane and kerosene have been studied as diluents. Xylene is found to be the most efficient. Scandium can be separated from most metals by selective extraction, and from gallium, thallium(III), bismuth, antimony(III), chromium(III), copper(II), iron(III), uranium(VI), cerium, zirconium, indium, thorium and titanium by selective stripping, in some cases combined with use of suitable complexing media to retain the other metals in the organic phase.     

Adsorption and inhibition effects of tribenzylamine in ethanol+water mixtures on a mercury electrode

The adsorption properties of tribenzylamine on mercury were studied using electrocapillary and C-E curves measurements in ethanol+water mixtures in various supporting electrolytes. With the increase of ethanol content a sudden decrease of the differential capacity to a minimum value was observed followed at negative potentials by an abrupt increase of the capacity to the value of the supporting electrolyte. These transition potentials were dependent on the percentage of ethanol and on the concentration of tribenzylamine.The observed behaviour was attributed to a two-dimensional association of the adsorbate in the double layer. The quantitative evaluation of the results fulfilled the theoretical relations for association in the film. Another support for this idea was obtained from the inhibition effect of tribenzylamine on several fast charge transfer reactions at the DME. The potential of the sudden decrease of the limiting diffusion controlled current was very near to the positive transition potential at the C-E curves. The inhibition effect decreased with ethanol content.     

IOn-exchange behaviour of several elements in mixed solvents

The distribution coefficients between the cation- and anion-exchangers Dowex 50 and Dowex 1, and aqueous solutions containing nitric or hydrochloric acid and organic solvents with or without amines or complexing agents, have been obtained for a number of metals including uranium, thorium, cerium, iron, copper, and nickel. The organic solvents were methanol, acetone and dimethylformamide; the amines were tributylamine and tribenzylamine, and the complexing agents EDTA and citric acid. Both batch and column methods were used.     

Simultaneous determination of antimony,arsenic and copper by neutron activation analysis

A rapid procedure has been developed for the mutual separation of antimony and arsenic using tribenzylamine as the extracting agent. The extraction behaviours of Sb(III), Sb(V), As(III), As(V) and Au(III) have been studied as a function of the acidity of the aqueous phase. Various factors which affect the extraction of these complexes have been studied and optimized. The procedure was then applied to lead base alloy for the simultaneous determination of antimony, arsenic and copper. Chemical recoveries were quantitative and only about one hour is required for the chemical processing of duplicate samples.     

Improved tribenzylamine-silver bromide extraction/atomic-absorption spectrophotometric method for the determination of silver in ores, related materials and zinc process solutions

An improved tribenzylamine extraction/atomic-absorption method for the determination of silver in ores, related materials and zinc process solutions is described. The method, which involves the separation of silver by a single methyl isobutyl ketone extraction of the tribenzylamine-silver bromide ion-association complex from ~ 0.5-2M sulphuric acid-0.14M potassium bromide, is simpler and more rapid than a previous method based on a triple chloroform extraction of the complex. Silver is stripped with 12M hydrochloric acid containing 1% thiourea as a complexing agent. Thiourea is destroyed with nitric and perchloric acids and silver is ultimately determined by atomic-absorption spectrophotometry in an air-acetylene flame, at 328.1 nm, in a 10% v v hydrochloric acid-1% v v diethylenetriamine medium. Cadmium and bismuth are partly co-extracted but do not interfere. Results obtained by this method are compared with those obtained previously by the tribenzylamine/chloroform extraction method and with those obtained by a direct acid-decomposition/atomic-absorption method.     

Synthesis of meso-tetraalkyltetrabenzoporphines

Stable complexes of zinc meso-tetralkyltetrabenzoporphines with tribenzylamine have been obtained by the template tetramerization of 3-R-methylenephthalimidines with zinc acetate in the presence of tribenzylamine or by the reaction of potassium phthalimide with the corresponding alkylmalonic acids. The structures of the compounds synthesized have been confirmed by their electronic absorption spectra, and in some cases also by their mass spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 61–64, January, 1984.     

Spectrophotometric determination of micro amounts of mercury,cadmium, and zinc by stepwise extraction with tribenzylamine

A rapid spectrophotometric method has been developed for the stepwise determination for mercury, cadmium, and zinc in mixtures. Optimal conditions have been established for the extraction efficiency of cadmium and mercury with a chloroform solution of tribenzylamine pre-equilibrated with hydrobromic acid. After addition of dithizone solution to the organic layers the absorbance at 490 nm or 510 nm is measured for mercury or cadmium, respectively. Even when the ratio of mercury, cadmium, and zinc is 10^-1 : 1 : 10^-5 , the metals can be determined successively.     

Gravimetric determination of tungsten with tetraphenylarsonium chloride after its extraction as thiocyanate

Small amounts of tungsten in natural and industrial samples can be freed from all important interfering elements by extraction of molybdenum by xanthate, reduction of tungsten by mercury and extraction of tungsten(V) thiocyanate into tribenzylamine, and finally back-extraction. The tungsten can be then determined as tetraphenylarsonium tungstate by precipitating it at pH 2-4, filtering it off and drying it at 110 degrees for 45 min. An overall error of 0.1-0.2% is obtained for 5-60 mg of tungsten.     

Mechanistic studies of radical-based processes. Use and misuse of EPR spectroscopy

The identification of the species observed by EPR spectroscopy in the SmI(2)-promoted coupling of N-(N', N'-dialkylaminoalkyl)benzotriazoles as substituted benzyl radicals is disputed on the basis of results obtained studying the model radical derived from tribenzylamine.     

Multiple hindered rotators in a gyroscope-inspired tribenzylamine hemicryptophane

A gyroscope-inspired tribenzylamine hemicryptophane provides a vehicle for exploring the structure and properties of multiple p-phenylene rotators within one molecule. The hemicryptophane was synthesized in three steps in good overall yield using mild conditions. Three rotator-forming linkers were cyclized to form a rigid cyclotriveratrylene (CTV) stator framework, which was then closed with an amine. The gyroscope-like molecule was characterized by (1)H NMR and (13)C NMR spectroscopy, and the structure was solved by X-ray crystallography. The rigidity of the two-component CTV-trismethylamine stator was investigated by (1)H variable-temperature (VT) NMR experiments and molecular dynamics simulations. These techniques identified gyration of the three p-phenylene rotators on the millisecond time scale at -93 °C, with more dynamic but still hindered motion at room temperature (27 °C). The activation energy for the p-phenylene rotation was determined to be ~10 kcal mol(-1). Due to the propeller arrangement of the p-phenylenes, their rotation is hindered but not strongly correlated. The compact size, simple synthetic route, and molecular motions of this gyroscope-inspired tribenzylamine hemicryptophane make it an attractive starting point for controlling the direction and coupling of rotators within molecular systems.     

Spectrophotometric determination of tungsten with thiocyanate

The yellow W(V) thiocyanate complex is formed by shaking sodium tungstate solution in 0.2-0.8M potassium thiocyanate and 4-5M hydrochloric acid, with mercury. It is extracted with 2% tribenzylamine solution in chloroform and measured at 410 nm. U, Ti, V, Cr, Fe, Co, Ni, Mn, Al, Pb, Sn, Bi, Pd, Sb and Cu do not interfere. Pt and Mo in amount equal to that of tungsten give errors of up to 0.4 and 2% respectively. The sensitivity is 0.013 mug ml and Beer's law is obeyed up to 24 mug ml .     

Studies on the reaction of 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone with tribenzylamine and diazabicyclo[2.2.2]octane in acetonitrile solvent

The reaction of chloranilic acid with two nitrogen nucleophiles, tribenzylamine and diazabicyclo[2.2.2]octane has been studied. Careful spectroscopic analysis showed that the product in both cases is a radical ion pair of Q^.-, A^.+ type. Stoichiometry of the complex formed is of 1:1 type. Mechanism of the reaction is proposed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Center-to-propeller and propeller-to-propeller stereocontrol in a series of macrobicyclic tri-λ-phosphazenes

Center-to-propeller stereocontrol in a family of macrobicyclic, double-propeller shaped tri-λ⁵-triphosphazenes remains constant in the upper tribenzylamine fragment as the size of the pivotal group at the lower tris(phosphane) fragment is gradually increased. In contrast the propeller-to-propeller stereocontrol diminishes as a result of the increasing conformational lability in the lower hemisphere.     

Stereodynamics of tribenzylamine

¹H DNMR studies in conjunction with EFF calculations for tribenzylamine indicate a preference for that conformer having C₃ symmetry and the presence of minor rotamers having one phenyl group anti to the lone pair.     

Effect of aniline derivatives on the extraction of cobalt with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one in toluene

Summary The effect of aniline derivatives [4-methylaniline=4-toluidine, 3,4-dimethylaniline=3,4-xylidine, N,N-dimethylaniline and tribenzylamine (Am)] on the extraction of cobalt from sulphate, nitrate and perchlorate aqueous media of 1.0M ionic strength with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one (HL) in toluene, has been quantitatively studied. With both primary amines a synergic effect was found owing to theAmH·CoL ₃ ion pair extraction. TheAmH·CoL ₃ average formation constant, from CoL ₂ andAmH·CoL, was logK _s =3.7 and 3.8 forAm=4-toluidine and 3,4-xylidine respectively. With N,N-dimethylaniline and tribenzylamine which are poorly protonated in the cobalt extractionpH range (4–6), no noticeable synergism was observed.On leave from: Department of Inorganic Chemistry, Chemical Faculty, Ignacy Lukasiewicz Technical University, PL-35-959 Rzeszow, Poland     

Elektrochemische oszillationen bei der inhibierten kupferabscheidung an der quecksilberelektrode

In the polarographic deposition of Cu²⁺ and Bi³⁺ in the presence of tribenzylamine in acid solution there is a potential region with a negative characteristic. With suitable external circuitry, electrochemical oscillations can be produced in this potential region. The influence of applied potential, working resistance, stirring of the electrolyte, temperature as well as reactant and inhibitor concentration, were tested. The oscillations occur with periodic adsorption and desorption of the inhibitor coupled with periodic concentration changes of the reactant in the neighbourhood of the electrode during the polarographic reduction.     

Formation and cure of novolacs: NMR study of transient molecules

High-resolution magnetic resonance spectroscopy has been used to investigate three areas of novolac resin chemistry: first, the lifetimes of glycol species in formalin under acid and base conditions and the reactivity of methylene glycol towards alcohols; second, the in situ identification of novolac resin intermediates; third, the novolac–hexamethylenetetramine cure mechanisms. It is shown that the mean lifetime of a given glycol species is an order of magnitude shorter under basic conditions than under an acid of equal normality. The ratio of the equilibrium constants for the addition of methylene glycol to methanol, benzyl alcohol, and phenol was measured as 70:20:1. New reactive intermediates were discovered while monitoring the reaction of phenol and formalin. The reactions of various phenols with hexamethylenetetramine were studied, and short-lived benzoxazines were detected at 100–120°C whenever ortho hydrogen was available on the phenolic nucleus. The NMR peak assignments in the reaction sequence: benzoxazine, dibenzylamine, tribenzylamine, diphenylmethane are presented. Spectra of the very elusive p-benzylamines of 2,6-xylenol were recorded at 100–155°C. At 170°C, the lifetimes of these p-benzylamines are too short to afford proton resonance spectra. No evidence of hexahydrotriazine or (CH₂ = N-CH₂)₃N type structures was found in 100 MHz NMR spectra of reaction mixtures of a phenol and hexamethylene-tetramine.     

On the protonation of a macrobicyclic cage: an inert tribenzylamine fragment and three robust aminophosphonium units

The protonation of a macrobicyclic cage with four intracyclic nitrogen atoms (one included into a tribenzylamine fragment and the other three into iminophosphorane units) led to tris(aminophosphonium) cations. In the salts, the three anions are situated outside the internal cavity although intercalated within the grooves of its macrobicyclic skeleton. The three aminophosphonium units are remarkably resistant to hydrolysis.     

A rapid and convenient method for the synthesis of aldoximes under microwave irradiation using in situ generated ionic liquids

We have developed a chemoselective, simple and efficient method for the preparation of aldoximes using microwave irradiation in the presence of tribenzylamine or 1,4-diazabicyclo[2.2.2]octane or 1-benzyl-4-aza-1-azoniabicyclo[2.2.2]octane bromide as bases and useful precursors for in situ generation of ionic liquids.     

TBA浸渍树脂对钯的吸附性能及应用

研究了三苄胺浸渍树脂吸附钯的机理、溶液酸效应、吸附等温线、吸附容量1吸附速率及操作条件等，用于测定钯催化剂中微量钯，取得了较好的效果。