Permselectivity between two anions in anion exchange membranes crosslinked with various diamines in electrodialysis

A membranous copolymer crosslinked with divinylbenzene reacted with N,N,N′,N′-tetra-methylethylenediamine, N,N,N′,N′-tetramethyl-1,3-propanediamine, and N,N,N′,N′-tetramethyl-1,6-hexanediamine to prepare highly crosslinked anion exchange membranes. More than 80% of both tertiary amino groups of the diamines reacted with chloromethyl groups of the membrane to form crosslinkage. After formation of the high crosslinkage of the membrane was confirmed with dialysis of a neutral molecule, electrochemical properties of the obtained membranes (mainly, relative transport number between two anions in electrodialysis) were evaluated: nitrate ions to chloride ions, sulfate ions to chloride ions, fluoride ions to chloride ions, and bromide ions to chloride ions. Though larger anions, in general, were difficult to permeate through the membranes due to high crosslinkage, the number of methylene groups of the diamines (which means the increase in hydrophobicity of anion exchange groups) also affected the relative transport number between two anions. The lower the hydration of anions, the higher the relative transport number of the anions through the membranes with the hydrophobic anion exchange groups. © 1996 John Wiley & Sons, Inc.     

Five-membered 2,3-dioxo heterocycles: LXII. Reaction of 3-aroyl-1H-pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones with N,N′-dihydroxycyclohexane-1,2-diamine. Unusual rearrangement in the spiro[quinoxaline-2,2′-pyrrole] system

3-Aroyl-1H-pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones reacted with N,N′-dihydroxycyclohexane-1,2-diamine to give 3-aroyl-1′,4,4′-trihydroxy-1-(2-hydroxyphenyl)-4a′,5′,6′,7′,8′,8a′-hexahydro-1′H-spiro[pyrrole-2,2′-quinoxaline]-3′,5(1H,4′H)-diones which underwent rearrangement into 1′-aroyloxy-4,4′-dihydroxy-1-(2-hydroxyphenyl)-4a′,5′,6′,7′,8′,8a′-hexahydro-1′H-spiro[pyrrolidine-2,2′-quinoxaline]3′,4,5(4′H)-triones via [1,4]-migration of the aroyl group. The product structure was proved by X-ray analysis.     

The effect of alkylating agent on the efficiency and selectivity of new polymeric anion exchangers

New anion exchangers for ion chromatography with functional groups of trimethylammonium and 3-chloro-2-hydroxypropyl-N,N-dimethylammonium were obtained. The synthesis included consecutive acetylation of a styrene-divinylbenzene copolymer containing 25% divinylbenzene, reductive amination of carbonyl groups, and subsequent alkylation. Iodomethane and epichlorohydrin were used as alkylating agents. The chromatographic properties of anion exchangers were studied by means of suppressed ion chromatography with conductometric detection. Anion exchangers with the 3-chloro-2-hydroxypropyl-N,N-dimethylammonium group are characterized by better selectivity and higher efficiency for polarizable nitrate and bromide ions, as well as for nonpolarizable chloride, fluoride, nitrite, phosphate, and sulfate ions, compared to those of sorbents with the trimethylammonium group.     

Solvent extraction of Zr(IV) and Hf(IV) with <Emphasis Type="Italic">N,N,N′,N′</Emphasis>-tetraoctyldiglycolamide

N,N,N′,N′-tetraoctyldiglycolamide (TODGA) was synthesized and characterized with elemental analysis, infrared spectrometry and nuclear magnetic resonance spectrometry. The synthesized TODGA was applied for the extraction and separation of Zr(IV) and Hf(IV) from nitric acid solutions. The performed studies include the effects of TODGA, nitric acid, nitrate ion, hydrogen ion, and metal ion concentrations as well as time and temperature. TODGA shows effective extraction of Zr(IV) and Hf(IV) from HNO₃ ≥ 3 M. However, the maximum separation factor (D _Zr/D _Hf) obtained using TODGA is 2.8.     

Influence of sulfate and nitrate uptake from aqueous solutions on surface exchange in Purolite A-520E resin

Removal of nitrate anions from aqueous solutions is the principal goal of many studies concerning water treatment. The ion exchanger capacity to remove nitrate from water was investigated using commercial type A-520E anion exchange resins. The nitrate and sulfate ion exchanger capacity, in static conditions, depends on the concentration of ions and on the pH value of the aqueous solution. The local structural environment exchanged on A-520E has been investigated by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX) and 2D and 3D atomic force microscopy (AFM). All images of the ion exchanger were obtained before and after contact with solutions that contain NO₃⁻ and SO₄²⁻ separately as well as mixtures of both.     

Quantum chemical simulation of low-basic AN-221(НСl) anion exchanger during the hydration and non-exchangeable absorption of phenylalanine

The formation of structures obtained during the hydration and non-exchangeable absorption of phenylalanine by a low-basic AN-221 ion exchanger in the НСl form is modeled in the work. Quantum chemical calculations are made using the Gaussian 03 program implementing the B3LYP hybrid density functional with the 6-31G++(d,p) basis set. The sequence of hydration and dissociation of functional groups of the ion exchanger is determined, the structure is optimized, and its formation energy during the non-exchangeable sorption of phenylalanine by the AN-221 (НСl) anion exchanger is estimated.     

Structure characterization and quantification of a new isoflavone from the arial parts of Phyllanthus niruri

A new isoflavone together with 5,7-dimethoxy-3,4′-dihydroxy-3′,8-di-C-prenylflavanonol and 5,3′-dihydroxy-6,7,4′-trimethoxyflavone has been isolated from the arial parts of Phylanthus niruri. Based on spectral methods, the structure of the new compound was elucidated as 6-hydroxy-7,8,2′,3′,4′-pentamethoxyisoflavone. The isolated isoflavone was quantified by gas chromatography couple with mass spectroscopy (GC–MS) in selected ion monitoring (SIM) mode. Suitable methods for quantification and extraction have been developed. The quantifying limit of this method was less than 5 ng/ml in 10 g (fresh weight) of sample. Recovery of isoflavone in spiked samples exceeded 62–72% while R.S.D. ranged from 1.0% to 6.1%. The results showed significant variation in the amount of this marker in methanol extract of Phylanthus niruri from Kushtia, Bangladesh and Java Island, Indonesia, even though the values were almost identical for most of the cases. Isoflavone was detected in all the samples ranging from 0.12% to 0.29%.     

Spectroelectrochemical detector for flow-injection systems and liquid chromatography

Flow-through spectroelectrochemical detectors for flow-injection systems and liquid chromatography are described. The detectors have a rectangular flow channel with a reticulated vitreous carbon working electrode followed by an open optical window. The dead volumes of the cells are 27 μl (liquid chromatography) and 80 μl (flow injection). In situ spectral monitoring of reaction products and intermediates for compounds that are both weakly and highly absorbing is demonstrated by using o-tolidine and N,N,N′,N′-tetramethyl-p-phenylenediamine. As a detector for flow-injection systems, components in two-component mixtures can be quantified. As a detector for liquid chromatography, simultaneous absorbance and electrochemical chromatograms allow more eluting compounds to be identified and quantified. Mixtures of nitro- and chloro-phenols are used to illustrate the simultaneous profiling of spectral and redox properties.     

Poly(N,N′-dichloro-N-ethyl-benzene-1,3-disulfonamide, N,N,N′,N′-tetrachlorobenzene-1,3-disulfonamide, poly(N,N′-dibromo-N-ethyl-benzene-1,3-disulfonamide, and N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide catalyzed formylation of amines and alcohols using ethyl formate under microwave irradiation

A simple, rapid, and efficient procedure for formylation of primary and secondary amines and alcohols using ethyl formate catalyzed with poly(N,N′-dichloro-N-ethyl-benzene-1,3-disulfonamide (PCBS), N,N,N′,N′-tetrachlorobenzene-1,3-disulfonamide (TCBDA), poly(N,N′-dibromo-N-ethyl-benzene-1,3-disulfonamide (PBBS) and also N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide (TBBDA) was adopted. The reactions were performed under microwave irradiation with high yields.     

Komplexone XLIII. Die Komplexe des dreiwertigen Antimons mit Polyaminocarboxylaten

If a strong base is added to solutions containing complexes of trivalent antimony with aminopolycarboxylates, these ligands are displaced, and oversaturated solutions of antimony (III) hydroxide are formed. This reaction has been used to investigate the formation of complexes of Sb^III with the following ligands: N′-hydroxyethyl-ethylenediamine-N,N,N′-triacetate ion, ethylenediamine-N,N,N′,N′-tetraacetate ion, 1,2-diaminocyclohexane-N,N,N′,N′-tetraacetate ion, and diethylenetriamine-N,N,N′,N″,N″-pentaacetate ion.     

Synthesis and transformations of bis(polychloroethylideneaminosulfonyl)- and bis(polychloroethylideneaminosulfonyl)-substituted derivatives of biphenyl, diphenyl oxide, and diphenylmethane

Reactions of N,N,N′,N′-tetrachlorobiphenyl-4,4′-disulfonamide, 4,4′-methylenebis(N,N-dichlorobenzenesulfonamide), and 4,4′-oxybis(N,N-dichlorobenzenesulfonamide) with 1,2-dichloroethylene and trichloroethylene open convenient synthetic approach to highly electrophilic bissulfony limines of dichloroacetic aldehyde and chloral: N,N′-bis(polychloroethylidene)biphenyl-4,4′-disulfonamides, 4,4′-methylenebis[N-(polychloroethylidene)benzenesulfonamides] and 4,4′-oxybis[N-(polychloroethylidene)benzenesulfonamides]. The synthetic opportunities of the bisazomethines obtained were demonstrated by examples of their reactions with water, methanol, chloroacetamide, and toluene where products of O-, N-nucleophiles addition to the azomethine bond and products of C-amidoalkylation of aromatic compound with imines were formed.     

The stationary phase capacity concept in elution liquid chromatography

The stationary-phase capacity concepts derived from linear capacity are discussed in connection with the needs of analytical, trace enrichment analysis and preparative chromatography and shown to be unsuited to them. A new concept based on stationary-phase saturation and called “available capacity” is proposed. It generalizes the ion-exchanger exchange capacity to adsorption and partition chromatography when the sampling solvent is the mobile phase. In linear elution chromatography the available capacity is proportional to the solute concentration C_o and to the analytical capacity factor k′ for given C_o and k′ values, it is independent of the nature of the solute. Furthermore, when both the concentrations and the analytical capacity factors (practically, for C_o ≥ 1 M and k′ ≥ 10, respectively) are high, the available capacity reaches a value roughly independent of C_o and k′, called “maximum available capacity” and related only to the number of sites available on the stationary phase. Numerous measurements were made in ion-exchange, adsorption, and reversed-phase chromatography. For solutes having a single polar functional group interacting with the stationary phase, the orders of magnitude of the maximum available capacity are 1.2 mmole g^?1 for a classical silica gel (Partisil 5 μm, 400m^?2 g^?1 with a water content of 2.7%); 1.8 mmole g^?1 for the Lichroprep RP 8 octyl bonded silica (11.6% carbon content); 3.8 mmole g^?1 for an anion exchanger resin of Dowex type.     

Five-membered 2,3-dioxo heterocycles: LX. Reaction of 3-aroyl-1H-pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones with cyclic enehydrazino ketones. Crystalline and molecular structure of N-[3′-benzoyl-4′-hydroxy-1′-(2-hydroxyphenyl)-6, 6-dimethyl-2,4,5′-trioxo-1′,4,5,5′,6,7-hexahydrospiro[indole-3,2′-pyrrol]-1(2H)-yl]-3-nitrobenzamide

3-Aroyl-1H-pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones react with N′-(5,5-dimethyl-3-oxocyclohex-1-en-1-yl)benzohydrazides to give the corresponding N-[3′-aroyl-4′-hydroxy-1′-(2-hydroxyphenyl)-6,6-dimethyl-2,4,5′-trioxo-1′,4,5,5′,6,7-hexahydrospiro[indole-3,2′-pyrrol]-1(2H)-yl]benzamides. The molecular and crystalline structure of one of the products, N-[3′-benzoyl-4′-hydroxy-1′-(2-hydroxyphenyl)-6,6-dimethyl-2,4,5′-trioxo-1′,4,5,5′,6,7-hexahydrospiro[indole-3,2′-pyrrol]-1(2H)-yl]-3-nitrobenzamide, was determined by X-ray analysis.     

The synthesis of ribonucleotide-5′-(5-Iodoindol-3-ol) and (4-methylcoumarin-7-ol) esters for the histochemical demonstration of nucleases

The syntheses of ribonucleotide-5′ monoesters with 5-iodoindol-3-ol and 5′-uridylic acid and 5′-adenylic acid monoesters with 4-methylcoumarin-7-ol has been accomplished by the reaction of phosphorodichloridates with various 2′,3′-O-isopropylidene ribonucleosides, followed by hydrolysis and anion exchange chromatography.     

The Synthesis and Application of Novel Nitrating and Nitrosating Agents

Alcohols and phenols are efficiently nitrated with thionyl chloride nitrate or thionyl nitrate, even in the presence of an aromatic moiety. While thionyl chloride nitrate is suitable for nitration of primary OH-groups in carbohydrates, thionyl nitrate is reactive enough to react with secondary OH-groups as well. These reagents permit the highly selective nitration of the 5′-,2′5′- and 3′, 5′-OH-groups of ribonucleosides to produce either mono-or diprotected nitro derivatives in high yields. Carbon acids and the enol form of some ketones are efficiently nitrated with trifluoromethanesulfonyl nitrate/potassium tert-butoxide. Lutidine N-oxide (2,6-(CH₃)₂C₅H₃N O) was found to have a marked effect on nitration reactions. Similarly, thionyl chloride nitrite and thionyl nitrite exhibit an excellent capacity for nitrosation of the aforementioned substrates.     

Electrochemical and chemical reduction of pyridyl-substituted pyrrolidinofullerenes

Using cyclic voltammetry, it is shown that formal reduction potentials of pyridyl-substituted pyrrolidinofullerenes are shifted to negative values as compared with formal potentials of the corresponding redoxtransitions of C₆₀, which indicates weakening of the acceptor properties of the fullerene fragment. NIR spectrophotometric and EPR spectroscopic studies show that cis-2′,5′-di-(4-pyridinyl)pyrrolidino-[3′,4′:1,2][60]fullerene is reduced with 1,8-diazobicyclo[5.4.0]undec-7-ene and morpholine to give a radical anion.     

Comprehensive Analysis of DNA Strand Breaks at the Guanosine Site Induced by Low‐Energy Electron Attachment

To elucidate the role of guanosine in DNA strand breaks caused by low‐energy electrons (LEEs), theoretical investigations of the LEE attachment‐induced C? O σ‐bonds and N‐glycosidic bond breaking of 2′‐deoxyguanosine‐3′,5′‐diphosphate (3′,5′‐dGMP) were performed using the B3LYP/DZP++ approach. The results reveal possible reaction pathways in the gas phase and in aqueous solutions. In the gas phase LEEs could attach to the phosphate group adjacent to the guanosine to form a radical anion. However, the small vertical detachment energy (VDE) of the radical anion of guanosine 3′,5′‐diphosphate in the gas phase excludes either C? O bond cleavage or N‐glycosidic bond breaking. In the presence of the polarizable surroundings, the solvent effects dramatically increase the electron affinities of the 3′,5′‐dGDP and the VDE of 3′,5′‐dGDP^?. Furthermore, the solvent–solute interactions greatly reduce the activation barriers of the C? O bond cleavage to 1.06–3.56 kcal mol^?1. These low‐energy barriers ensure that either C_5′? O_5′ or C_3′? O_3′ bond rupture takes place at the guanosine site in DNA single strands. On the other hand, the comparatively high energy barrier of the N‐glycosidic bond rupture implies that this reaction pathway is inferior to C? O bond cleavage. Qualitative agreement was found between the theoretical sequence of the bond breaking reaction pathways in the PCM model and the ratio for the corresponding bond breaks observed in the experiment of LEE‐induced damage in oligonucleotide tetramer CGTA. This concord suggests that the influence of the surroundings in the thin solid film on the LEE‐induced DNA damage resembles that of the solvent.     

Further aspects of the thermal rearrangement of 1-aryl-2-cyano-3,3-diphenyldiazetidin-4-ones

The title reaction has been shown by a ¹⁵N labelling study to proceed via a [3.3]-sigmatropic rearrangement. The 1,2-migration of halogen atoms has been observed during the rearrangement of 1-(2′,6′-dichlorophenyl)- and 1-(2′,4′,6′-tribromophenyl)-2-cyano-3,3-diphenyldiazetidin-4-ones.     

Ion chromatography on carbon clad zirconia modified by diazonium chemistry and functionalized latex particles

This work explores the potential of 3 μm carbon coated zirconia particles as a stationary phase for ion chromatography for the separation of organic acids and inorganic ions. A 4-phenylsulfonic acid functionality is introduced onto the carbon surface by reducing 4-phenylsulfonic acid diazonium chloride with borohydride in the presence of carbon clad zirconia particles. The elemental sulfur analysis gave 132 μeq-SO(3)H/g carbon clad zirconia and 2% S atomic concentration by XPS analysis. The -SO(3)(-) groups serve as electrostatic anchors for latex nanoparticles bearing quaternary triethylamine functional groups. The agglomeration step in 5 × 0.4 cm i.d. columns converts the packed particles into an anion exchanger. The breakthrough curves with nitrate indicate a capacity of 3 μeq/column. Separation of common organic acids and inorganic ions using carbonate eluent and suppressed conductivity detection yield plate heights (H) of 0.023-0.05 mm.     

Influence of diluent on radiolysis of amides in organic solution

The radiolytic behavior of N,N,N′,N′-tetraoctyldiglycolamide, N,N′-dimethyl-N,N′-dioctyl-2-(3′-oxapentadecyl)malonamide, and N,N-dioctylhexanamide in n-dodecane was investigated by irradiation with γ-rays and electron pulses. The results showed n-dodecane has a sensitization effect on the radiolysis of these amides, owing mainly to a charge transfer from radical cations of n-dodecane to the amide molecules in the primary process observed in pulse radiolysis. This result was supported by the difference in the ionization potentials between n-dodecane and these amides.