Potentiometric sensors based on organic ion exchangers for determining tetraalkylammonium salts

Potentiometric sensors with plasticized polymer membranes based on organic ion exchangers, tetraalkylammonium dodecyl sulfates (benzyldimethyldodecylammonium, benzyldimethyltetradecylammonium, dimethyldistearylammonium), have been proposed for the determination of quaternary ammonium salts in model solutions and KATAPAV technical solutions. The thermal stability, composition, and solubility product have been estimated. It has been shown that ion associates are stable to 60?C70°C, K _S varies in the range from 2 × 10^?8 to 5 × 10^?10. The basic electrochemical parameters of the sensors have been determined as well, such as linearity ranges of the electrode function (5 × 10^?5 (5 × 10^?6)?1 × 10^?2 (1 × 10^?3) M) and slopes of the electrode functions (47?C59 mV/pc), response time (60?C90 sec), potential drift (2?C3 mV/day), operation period (3?C4 months), limits of detection for tetramethylammonium salts (1 × 10^?5?4 × 10^?7 M).     

Isolating benzenium ion salts

When partnered with carborane anions, arenium ions are remarkably stable. Previously investigated only at subambient temperatures in highly superacidic media, protonated benzene is readily isolated as a crystalline salt, thermally stable to >150 degrees C. Salts of the type [H(arene)][carborane] have been prepared by protonating benzene, toluene, m-xylene, mesitylene, and hexamethylbenzene with the carborane superacid H(CB(11)HR(5)X(6)) (R = H, Me; X = Cl, Br). They have been characterized by elemental analysis, X-ray crystallography, NMR and IR methods. Solid-state (13)C NMR spectra are similar to those observed earlier in solution, indicating that lattice interactions are comparable to solution solvation effects. The acidic proton(s) of the arenium cations interact weakly with the halide substituents of the anion via ion pairing. This is reflected in the dependence of the C-H stretching frequency on the basicity of the carborane anion. Bond lengths in the arenium ions are consistent with predominant cyclohexadienyl cation character, but charge distribution within the cation is less well represented by this resonance form. Structural and vibrational comparison to theory is made for the benzenium ion (C(6)H(7)(+)) with density functional theory at B3LYP/6-31G and B3P86/6-311+G(d,p) levels. The stability of these salts elevates arenium ions from the status of transients (Wheland intermediates) to reagents. They have been used to bracket the solution-phase basicity of C(60) between that of mesitylene and xylene.     

Magnetism in organic radical ion salts based on nitronyl nitroxide derivatives substituted with heterocyclic aromatic hydrocarbons

Radical cation and anion salts of the neutral organic radicals, 2-imidazolyl nitronyl nitroxide (2-IMNN) and 2-benzimidazolyl nitronyl nitroxide (2-BIMNN), have been prepared and their magnetic properties studied by SQUID magnetometry. The radical salts exhibit one-dimensional (1-d) antiferromagnetic (AFM) intermolecular interactions with the exchange coupling J/k between −0.8 and −6.3 K, which are significantly reduced from those observed in the two neutral radicals, while 2-IMNN shows an AFM interaction with J/k=−88 K within the molecular dimers and 2-BIMNN has quasi 1-d ferromagnetic (FM) intermolecular interactions with J/k=+22 K (intrachain) and zJ′/k=+0.24 K (interchain). The magnetic properties of the nitronyl nitroxide and iminonitroxide derivatives having molecular structure related to 2-IMNN have also been investigated. In 2-benzimidazolyl iminonitroxide (2-BIMIN), the FM interaction observed in 2-BIMNN is replaced by strong 1-d AFM interaction with J/k=−11.7 K.     

Effect of organic ion on the separation of salts by nanofiltration membranes

The aim of this study is to investigate the transport mechanism of NaCl through nanofiltration membranes in mixed solutions. A model based on the Spiegler–Kedem and Perry–Linder models has been developed. Concentration polarization effects of an organic ion and NaCl were not included in the previous studies. The effects of concentration polarization on salt removal were added to the model. Reactive Black 5 (RB5) was used as an organic ion in the rejection of NaCl by DS5 membrane in all experimental runs. Different concentrations of RB5 and NaCl have been studied and a coefficient of the gel polarization effect of dye on salt removal (α) was defined depending on molar concentration ratios of dye and NaCl. Experimental and calculated results were shown to be in good agreement.     

Porous ceramics based on silicon carbide

A method was described for producing porous ceramics based on ultradispersed fibrous silicon carbide in an autonomous protective atmosphere. The protective atmosphere is formed by carbon dioxide being released in the synthesis.     

离子对分离和抑制电导检测法测定四乙基铵和四丁基铵根离子

建立了季铵盐的离子色谱分析方法.采用Dionex DX-500 型离子色谱仪,C18柱,电导检测器,以30%乙腈和10 mmol/L甲烷磺酸混合溶液为流动相,流量为1.00 mL/min.四乙基溴化铵和四丁基溴化铵的质量浓度和峰面积的相关系数分别为0.9996和0.9994;线性范围分别为10～80 mg/L和20～120 mg/L;检出限分别为0.28和0.76 mg/L;RSD分别为1.3%、 2.5%.该方法可用于分析水溶液中季铵盐的含量.     

Lifetime studies on the phosphorescence of the tetrahedral tetrahalomanganate ion in fused salts and solids

The phosphorescence of tetrabutylammonium tetrahalomanganate salts has been investigated, both in the crystal and in the fused salt. The lifetime behavior of the ⁴T₁ → ⁶A transition in these tetrahedral systems is extremely unusual: The phosphorescence remains in the low viscosity melt; the bromide lifetime is ten times smaller than the chloride at room temperature, but about twenty times larger at 130°C; there is highly specific structure in the lifetime data of the solid which correlates with thermal phase transitions. Dilution experiments demonstrate that cooperative effects and electronic charge transfer processes are not important in these species. An explanation is suggested in terms of both low Franck—Condon factors and of frequency or Stokes shift of accepting modes for vibronically-induced radiative decay by the steric packing effects of the neighboring organic ion. Experiments for distinguishing the effects of these two mechanisms are suggested.     

Monitoring the removal of soluble salts from ancient tiles by ion chromatography

The application of ion chromatography, conductometry and total carbon analysis to the study of desalination of 18th century tiles and mortars is described. Ion chromatography is shown to be a simple and adequate technique for the identification and quantitative analysis of ions which are extracted during desalination. Chloride, nitrate, sulphate, carbonate, sodium, potassium, calcium and magnesium were always found in the immersion waters, and occasionally also nitrite and oxalate.     

Liquid-membrane dicyanoargentate-sensitive electrodes based on quaternary ammonium salts

Several quaternary ammonium salts have been synthesized and comparisons made of their efficiency as exchange substrates in dicyanoargentate-sensitive electrodes. The electrode prepared from hexadecyltrioctylammonium dicyanoargentate shows the best performance characteristics and has been studied in more detail. Its Nernstian response range is 10(-1)-10(-4)M, the optimum pH range is 10.6-12.6, and the detection limit is 3 x 10(-5)M. It is suggested that the detection limit of the electrode is controlled by interference from cyanide ions, and the difference between detection limits obtained with the various electrodes is discussed in the light of this. Selectivity coefficients for various interfering ions have been determined and related to the extractability of the ions. The electrode has been applied to determination of silver in cyanide-containing plating solutions.     

Sorption properties of polysulfones based on diallylaminophosphonium salts

The sorption properties of polysulfones based on diallylaminotris(diethylamino)phosphonium tetrafluoroborate and chloride were studied. The diallylaminotris(diethylamino)phosphonium tetrafluoroborate polysulfone shows rather high sorption capacity with respect to rhenium(VI) and good kinetic characteristics of sorption. When both Re(VII) and Mo(VI) are present in acidic or weakly acidic solutions, rhenium can be separated from molybdenum by the ion exchanger in question. At pH > 6, these metals are extracted together.     

New chiral ionic liquids based on imidazolinium salts

The preparation and application of a new series of chiral ionic liquids are described. The salts are based on imidazolinium cations. Some of the cations also incorporated an axial chirality at the C(2) position next to the central chirality. These cations display a very high rotational barrier along the arene–imidazolinium axis. Furthermore, an analogue with a chiral anion was prepared. The salts have low melting points. Their potential as solvents and as chiral shift reagents was explored, resulting for the first time in an example of a chiral ionic liquid as a shift reagent for a neutral compound.     

The initiation process in the polymerization of tetrahydrofuran with carbonium ion salts

The initiation process for the polymerization of tetrahydrofuran with (C₆H₅)₃C⁺SbCl₆^? has been studied. Two mechanisms have been considered: a cation-addition process, and a process in which tetrahydrofuran donates a hydride ion to the cation of the initiator to form triphenylmethane. The biscarbonium salt [(C₆H₅)₂C⁺C₆H₄CH₂]₂(SbCl₆^?)₂ has been synthesized and used to initiate the polymerization of tetrahydrofuran. The results are consistent with the hydride-ion mechanism but may be inconclusive because of chain transfer. NMR experiments with 0.05–0.2M solutions of initiator in tetrahydrofuran show that triphenylmethane is rapidly produced in an amount equal to the molar amount of initiator originally present. Some NMR evidence for the presence of an acetal end group in the polymer has been obtained. It is concluded that the initiation process in this system definitely involves the formation of triphenylmethane, although a detailed, unique mechanism cannot be selected at this time.     

Thermolysis of 1,2-dithiolylium salts in the ion source of the mass spectrometer

1,2-Dithiolylium salts are thermolysed in the ion source of a mass spectrometer; some salts (group I) undergo thermolysis to give a stable dithiolyl radical where subsequent ionization gives rise to a mass spectrum in which the parent ion corresponds to the dithiolyl ion. The radical may be stabilized before ionization by expulsion of a hydrogen atom to form a neutral dithiole derivative, and then mass spectra exhibit abundant molecular ions corresponding to such dithiole derivatives.Other salts (group II) may expel a proton with formation of a carbene and subsequent dimerization to a tetrathiafulvalene.The thermolytic behaviour of 1,2-dithiolylium salts is compared with their electrochemical behaviour and several analogies are found.     

Cyclic dithio-carbenium ion salts and their conversion to ketene dithioacetals

1,2-Ethanedithiol and 1,3-propanedithiol were treated with perchloric acid in acetic anhydride to give 2-methyl-1,3-dithiolan-2-yl and 2-methyl-1,3-dithian-2-yl perchlorates, respectively, which were converted to ketene dithioacetals by deprotonation with tertiary amines.     

Ionic liquids based on N-alkyl-N-methylmorpholinium salts as potential electrolytes

Ionic liquids based on N-alkyl-N-methylmorpholinium salts have been synthesized and the physical and electrochemical characteristics of this family of ionic liquids have been investigated for use as electrolytes.     

Star-shaped supramolecular ionic liquid crystals based on pyridinium salts

Series of novel star-shaped liquid crystals containing [1,1?-biphenyl]-4,4?-diyl diisonicotinate mesogens with various counterions (Br^?, B-SO₃^?,C-SO₃^?,H₂PO₄^?, BF₄^?) have been synthesized and characterized, which display a nematic phase. The molecular structures of the liquid crystals, thereof consisting of rod-like mesogens linked together by different long alkyl spacers to a small disc-like core of central benzene-1,3,5-triyl triisonicotinate, have been fully characterized by ¹H NMR. Their thermal and supramolecular organization behaviours have been studied by combining polarized optical microscopy, differential scanning calorimetry and small-angle X-ray scattering. These investigations showed that the mesophase temperature range increased with increasing alkyl chain length and the clearing point decreased with increase of anion size. These star-shaped liquid crystals have a long and ordered molecular structure, the electron delocalization of the π-π stacking conjugation effect and the electrostatic attraction of ionic make them have good ferroelectric properties and ionic conductivity properties. The interest in preparing ionic liquid crystal with a nematic phase lies in the technological applications as it is well known that the nematic phase has the highest fluidity of all liquid crystalline phases and hence the possibility to align it by applying an external electric/magnetic field, commonly used in electro-optical devices.