Volumetric properties of water–poly(acrylic acid) salt systems from the pure solid to highly concentrated solutions

Volumetric properties of poly(acrylic acid) alkali-metal salts (Li, Na, K, Rb, and Cs) with different degrees of neutralization and water contents were studied in the range from pure solid to highly concentrated solutions. The apparent partial molar volume ?₂ of the polymer and the partial molar volume V₁ of water were calculated from density data. The value of ?₂ decreased with decreasing polymer concentration and eventually leveled off. Values of V₁, which at low water contents were much smaller than that of free water, increased with increasing water content and eventually reached a constant value equivalent to that of free water, thus indicating the appearance of free water. Water contents corresponding to the appearance of free water increased in the order of Li < Na < K < Rb < Cs, differing from the usual trend of hydration numbers observed in dilute solutions. The change of the slope of the plots of V₁ versus composition suggested a change in the hydration mechanism. For Li, Na, and K salts, the limiting values of V₁ at very low water content is considerably smaller than the 18 cm³/mol of free water. In contrast, for Rb and Cs salts, these values were relatively large, indicating the relatively weak electrostriction effects of these ions.     

A method for controlled stoichiometry intercalation of alkali metals in layered metal dichalcogenide crystals

Crystals ofLi_yTiS₂ (0 < y < 1) and2HA_yTaX₂ (A =Li, Na, K; 0 < y < 1; X =S, Se) have been prepared by equilibration of the unintercalated crystals with a source powder of the desired alkali ion stoichiometry via the alkali vapor pressure of the compounds at 400–650°C. Crystals of 1 cm² area were intercalated. The final stoichiometry of the crystals is in good agreement with that expected from the source.     

Effect of a catechol segment in a polyether chain on the complexing ability of some phosphonate and quinoline monopodands

The complexing ability of monopodands with o-diethoxyphosphinylmethoxyphenyl and 8-quinoline end groups, containing both ethylene glycol and catechol units in the polyether chain, was studied by conductimetry in tetrahydrofuran-CHCl₃. Replacement of ethvlene glycol by catechol changes the efficiency insignificantly, but in a number of cases leads to some increase in K/Li and k/Na selectivity of phosphonate podands, and the K/Li and Na/Li selectivity of quinoline podands.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2611–2615, November, 1989.     

Search for internal diagonals in polyhedration of reciprocal systems by the algorithm for topological correction of lists of simplexes of different dimensions

The algorithm for topological correction of lists of simplexes of different dimensions was used for analyzing the published methods for determining internal diagonals in polyhedration of reciprocal systems. By this algorithm, errors were found in the polyhedration of the quaternary systems Ca,Na,K‖F,MoO₄, K,Na,Li‖Cl,NO₃, Ba,Na,K‖F,MoO₄, Na,K‖Cl,NO₃,NO₂, and Li,K,Ba‖F,WO₄ and the quinary system Li,K,Ca,Ba‖F,WO₄, which were used for illustrating the application of the methods. Advantages of the algorithms were demonstrated in cases of competition of internal secants.     

Electronic and geometric structure analysis of neutral and anionic alkali metal complexes of the CX series (X = O,S, Se,Te, Po): The case of M(CX) n = 1–4 (M = Li,Na) and their dimers

Bonding mechanisms, potential energy curves, accurate structures, energetics, and electron affinities are obtained for all M(CX)_1–3 species with M = Li, Na, and X = O, S, Se, Te, and Po, at the coupled-cluster level with triple-ζ quality basis sets. We discuss and rationalize the trends within different molecular groups. For example, we found larger binding energies for M = Li, for CX = CPo, and for the tri-coordinated (n = 3) complexes. All three facts are explained by the fact that the global minimum of the titled complexes originate from the first excited ²P (2p¹ for Li or 3p¹ for Na) state of the metal, with each ligand forming a dative bond with the metal. All of the complexes, except Na(CO)₃, have stable anions, and their electron affinity increases as MCX < M(CX)₃ < M(CX)₂. This sequence is attributed to the binding modes of these complexes. The Li(CO)₃ and Li(CS)₃ complexes are able to accommodate a fourth ligand, which is attached to the system electrostatically. Finally, two Li(CO)₃ molecules can bind together covalently to make the ethane analog. The staggered conformer was found lower in energy and unlike ethane the CO ligands bend toward the neighboring Li(CO)₃ moiety. © 2019 Wiley Periodicals, Inc.     

Intramolecular chelation as a factor in the stereochemistry of anionic vinyl polymerization

The methylation (CH₃I) of 1,3-bis(2-pyridyl)butyllithium in THF at −78°C is highly meso-selective (>98%) but the selectivity decreases with increasing cation-size or -coordination. The reaction of 1,3-bis(2-pyridyl)butyllithium with other electrophiles such as i-C₃H₇Br, PhCH₂Cl, Me₃SiCl (CD₃)₂CO and 4-vinylpyridine is also stereoselective under these conditions giving meso-like products. On the other hand, addition of 2-vinylpyridine is only slightly selective (64%) and this is consistent with the 65% meso content of P2VP formed by polymerization in the presence of Li ion. The chemistry of the above reactions is rationalized by intramolecular coordination of Li or other cations by the penultimate 2-pyridyl group and this is supported by equilibria involving proton abstraction of 1,3-bis(2-pyridyl)butane and similar compounds by bases having Li, Na or K counterions. It is shown that the tendency for intramolecular chelation is highest for Li and lowest for K ion. Temperature dependence of the above equilibrium shows that intramolecular chelation of Li and Na ions is exothermic (−1.4 and −1.3 kcal respectively) whereas the AH for K ion is very small (−0.5 kcal). Entropies of chelation are slightly positive for Li (0.8 e.u.) and negative for Na and K ions (-2.60 and −0.40 e.u. respectively). The lack of stereoregular polymerization of 2-VP in the presence of Li ion is most likely due to the requirement that the Li ion of the newly formed 2-pyridyl anion is coordinated with the 2-pyridyl group of the previous asymmetric center. Thus it would appear that intramolecular coordination of metal ion by penultimate 2-pyridine does not necessarily lead to isotactic-polymerization.     

Infrared high temperature spectra of aluminium chloride and related species

Isothermal cells of nickel with diamon windows were used to study various melts and vapours by infrared emission, transmission and reflectance techniques in the 860 to 300 K range with an evacuable Fourier transform spectrometer.IR vapour spectra of AlX₃ (X = Cl, Br, I) and GaCl₃ in transmission and emission were measured between 700 and 50 cm^?1. A comparable signal/noise ratio between the transmission and emission spectra was obtained above 200 cm^?1, below 200 cm^?1 the transmission spectra had better quality. The dimer and monemer spectra were assigned in terms of $\text{D}$_2h and $\text{D}$_3h symmetry, respectively, and compared with earlier Raman and IR matrix isolation data.Emission spectra of chloroaluminates AlkAlCl₄ (Alk = Li, Na, K, Rb, Cs) were recorded as melts between 1500 and 50 cm^?1. Increasing distortion of the tetrahedral AlCl^?₄ ion in the series Cs<Rb<K<Na<Li was observed. Emission spectra of AlkAl₂Cl₇ (Alk = Li, Na, K, Cs) indicate $\text{D}$_3d symmetry for Al₂Cl^?₇ with a linear Al-Cl-Al bridge as proposed from earlier Raman data. As a demonstration of reflectance technique an IR spectrum of ZnAl₂Cl₈ at ambient temperature is presented.     

Die Strukturen von LiAlCl4 und NaAlCl4 als Funktion der Temperatur

Crystal Structures of LiAlCl₄ and NaAlCl₄ as a Function of Temperature The crystal structures of LiAlCl₄ (space group P2₁/c) and of NaAlCl₄ (space group P2₁2₁2₁) have been investigated as a function of temperature. The single crystal intensities of the Bragg reflections have been measured for LiAlCl₄ at 293, 326, and 364 K and for NaAlCl₄ at 293, 353, and 393 K. The interatomic distances of the AlCl₄ tetrahedra stay constant, the Li? Cl and Na? Cl distances increase by 0.025 Å/100 K. The occupation probabilities of the Li and Na positions do not change. The directions of the largest thermal vibrational amplitudes of the Li and Na atoms (approximately 0.30 Å at 293 K) point to faces of their coordination polyhedra.     

The synthesis and characterisation of novel dimethyl- and diphenyl-silanediolates

Dimethyl- and diphenylsilanediolates are key intermediates in the preparation of dimethyl- and diphenyl-siloxane polymers. Both dimethyl- and diphenylsilanediolates R₂Si(OM)₂, where R = Me or Ph, and M = Li, Na and K were synthesised by the reaction between dimethyl- and diphenylsilanediol and a metal or metal hydride (M/MH where M = Li, Na and K). The silanediolates were characterised by ²⁹Si, ¹³C and ¹H NMR, FTIR and mass spectroscopy.     

Kinetik und mechanismus der elektrochemischen reduktion von 2,2′-dipyridyl I. Primärprozesse: Vorgelagerte isomerisierung eines komplexes

Polarography and chronopotentiometry are used to study the primary processes of the reduction of 2,2′-bipyridine at mercury electrodes in aqueous solutions (12 < pH < 14). Bipyridine and its first reduction product are strongly adsorbed. The reduction is preceded by a complex equilibrium between bipyridine and the cation of the supporting electrolyte (Li, Na, K, Ba). Due to the great excess of the cations, the equilibrium is shifted completely to the side of the complex, which exists as cis- and trans-isomer. The cis-form is more stable, forming a chelate, the trans-form however is more easily reducible. The kinetic and thermodynamic data of the isomerization are determined. The first reduction product reacts irreversibly giving a substance which can be reoxidized to bipyridine via a radical intermediate.     

Oligomerization of vinyl monomers 20. Carbon-13 NMR of oligomers of 2-vinylpyridine. Studies of labelled end groups

Oligomers of 2-vinylpyridine initiated with Li, Na, K, and Rb salts of ¹³C-labeled or-unlabeled 2-ethylpyridine and terminated with ¹³C-labeled or -unlabeled methyl iodide were separated by liquid chromatography and analyzed by ¹³C-NMR of the initial or terminal CH₃ group. The stereochemistry of the three dyads which flank the initial or terminal methyl group could be determined and this allowed us to evaluate the stereochemistry of both methylation and vinyl addition. The methylation of the Li and Na salts of the oligomer anions is highly (> 95%) stereoselective and independent of chain length, whereas the stereoselectivity of the K and Rb salts is substantially less. These data indicate that the Li and Na oligomer and polymer anions exist in a chelated form in which the metal ion is complexed with the penultimate 2-pyridine group, the other counterions being chelated to a lesser extent. The stereochemistry of monomer addition was found to be less stereoselective than that of methylation for the Li and Na salts. In addition, the apparent meso-stereoselectivity of monomer addition of the Na, K, and Rb systems was greater than that of the Li ion. For the latter system, in particular, the mechanism appeared to be Markoff-like and consistent with different reactivities of anions flanked by a distinct dyad or triad stereochemistry. These data appear to be consistent with the intramolecular coordination that tends to hold the third asymmetric center close to the propagating carbanion.     

Die Systeme des Typs MCl/AlCl3/SO2 (M = Li,Na, K,NH4)

The MCl/AlCl₃/SO₂ Systems (M = Li, Na, K, NH₄) Phase diagrams of the ternary systems of the type MCl/AlCl₃/SO₂ were determined by measurement of SO₂ pressure, solubilities, and by thermal analysis. The complete phase diagram in the range from ?30 to +50°C is given for the case M = Na, partial diagrams for M = Li, K, NH₄. There exist solid compounds of the type MAlCl₄ · nSO₂ (M = Li, Na; n = 1.5 and 3) (M = K; n = 1.5 and 5) (M = NH₄; n = 5). Liquid phases can be obtained at room temperature and atmospheric pressure in the NaCl or LiCl containing systems.     

Synthesis of dimethyl carbonate from methanol and supercritical carbon dioxide

The synthesis of dimethyl carbonate (DMC) from methanol and supercritical carbon dioxide over various base catalysts has been studied. Compounds of group-I elements (Li, Na and K) were used as base catalysts. The promoter and the dehydrating agent were also used to enhance the yield of DMC. The effects of the catalysts, promoter and dehydrating agent on the yield of DMC were investigated. By-products such as dimethyl ether (DME) and C₁–C₂ hydrocarbons were formed with the DMC as a main product. The yield of DMC with different alkali metal catalysts ranked in the following order: K > Na > Li. The catalysts of the metal-CO₃ compounds were more effective than the metal-OH compounds in DMC synthesis. The maximum DMC yield reached up to about 12 mol% in the presence of K₂CO₃ (catalyst), CH₃I (promoter) and 2,2-dimethoxypropane (dehydrating agent) at 130–140°C and 200 bar. The reaction mechanism of DMC synthesis from methanol and supercritical carbon dioxide was proposed.     

Crucial effect of rubidium cation on catalytic activity of a polycrystalline gold electrode toward oxygen reduction reaction in alkaline media

Catalytic activity of a polycrystalline gold electrode toward oxygen reduction reaction (ORR) in aqueous alkaline media in the presence of various alkali-metal sulfates (M₂SO₄, M = Li, Na, K, Rb and Cs) was investigated by hydrodynamic voltammetry. The fraction of 4e^? pathway in low overpotentials (? 0.1 to ? 0.3 V) depended on the alkali-metal cations (Rb ? Na, K, Cs, Li). A complete 4e^? reduction of O₂ was only attained in the presence of Rb⁺ cation in the solution, which was comparable or even superior to that reported at the Au(100) single crystal electrode.     

Selective oxidation of primary alkanols into the “symmetrical” esters with the H<Subscript>2</Subscript>O<Subscript>2</Subscript>-MBr-HCl system

Oxidation of linear or branched primary alkanols with H₂O₂-MBr (M = Li, Na, K)-HCl system in water affords the corresponding “symmetrical” esters in almost quantitative yield.     

Prussian Blue-coated interdigitated array electrodes for possible analytical application

Thin films of iron(III) hexacyanoferrate(II) (Prussian Blue) were electrochemically deposited on interdigitated array (IDA) electrodes, yielding systems which can be considered as chemiresistors in sensing alkali metal ion concentrations in an adjacent electrolyte. This is due to the fact that the conductivity of the film being measured by a steady-state current on application of a voltage to the two-fingered electrodes of the IDA depends on both the redox stare of the film and the cation concentration in the electrolyte. From the dependence of the steady-state current on the electrode (bias) potential at variable cation concentrations for different alkali metal ions and for mixtures of alkali metal ions, the possibilities of analytical application were elucidated. In addition, by using the methods of staircase coulometry and scanning conductivity, the electron diffusion coefficient D_e was determined as a function of the redox state of Prussian Blue. It is concluded that Prussian Blue-coated IDA electrodes are, in principle, suitable as chemiresistors for the determination of alkali metal ion concentrations with increasing selectivity in the series Li < Na < K < Rb < Cs.     

Synergistic effects of alkali metals in the alkylation of naphthalene and toluene with ethene in the ArH–alkali metal systems in THF (ArH – naphthalene,phenanthrene)

The use of mixtures of metallic lithium and sodium in the naphthalene–alkali metal systems in THF leads to a synergistic acceleration of the naphthalene alkylation with ethene at room temperature and atmospheric pressure. The greatest synergistic effect is observed at a Li:Na molar ratio of 2:1. Under these conditions, the overall conversion of naphthalene into alkylation products (linear 1-alkylnaphthalenes and their dihydro derivatives) attains 88% after 24 h (a (Li + Na):C₁₀H₈ ratio is 2:1). The use of mixtures of metallic lithium and potassium in such systems results, however, in a synergistic retardation of the alkylation process. The strongest retarding effect is observed at a Li:K molar ratio of 1:1. The efficiency of the toluene alkylation with ethene in the naphthalene–alkali metal systems in THF is also increased on the replacement of lithium or sodium by their mixtures. The best results are obtained at a Li:Na molar ratio of 1:3. With this Li:Na ratio, toluene is almost quantitatively converted into linear and α-branched higher monoalkylbenzenes (24 h, (Li + Na):C₁₀H₈ = 2:1). The rate of the naphthalene alkylation with ethene in the presence of toluene is enhanced as well on an introduction of mixtures of lithium and sodium into the system. However the maximum of the activity is shifted here towards higher lithium content (Li:Na = 1:1). A similar synergistic effect of lithium and sodium was found on studying the toluene alkylation with ethene in the phenanthrene–Li–Na systems in THF (a (Li + Na):phenanthrene ratio is 3:1). An addition of potassium to sodium also considerably increases the efficiency of the toluene and naphthalene alkylation with ethene in the naphthalene-based systems. The possible mechanism of the alkali metal synergism in the above-mentioned alkylation reactions is discussed.     

Thermal analysis and thermochemistry of alkali metal hexachlorostannates

The thermal behaviour of alkali metal hexachlorostannates of general formula A₂SnCl₆ (A=Li, Na, K, Cs, Rb) has been studied by thermoanalytical methods (dynamic TG, DTG and DTA, and Q-TG). The compounds decompose upon heating with total (A=Li, Na) or partial (A=K, Rb, Cs) release of SnCl₄ molecules to the gaseous phase. The enthalpies of the decomposition process have been evaluated on the basis of the Van't Hoff equation and using dynamic TG curves. The thermochemistry of the compounds was thoroughly examined particularly, with regard to the enthalpies of formation and crystal lattice energies, as well as enthalpy changes characterizing the dissociation process. These data revealed that stability of the compounds markedly increase with an increase in the size of alkali metal cation.

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Zusammenfassung Mittels thermoanalytischer Methoden (dynamische TG, DTG, DTA, Q-TG) wurde das thermische Verhalten von Alkalimetall-hexachlorostannaten der allgemeinen Formel A₂SnCl₆ (A=Li, Na, K, Cs, Rb) untersucht. Die Verbindungen zersetzen sich beim Erhitzen unter totaler (A=Li, Na) oder partieller (A=K, Rb, Cs) Freisetzung von SnC₄-Molekülen, die in die Gasphase übergehen. Die Enthalpien des Zersetzungsprozesses wurden auf der Grundlage der Van't Hoffschen Gleichung unter Zuhilfenahme dynamischer TG-Kurven ermittelt. Die Thermochemie dieser Verbindungen wurde gründlich untersucht, in besonderem Hinblick auf Bildungsenthalpie und Kristallgitterenergie als auch auf Enthalpieänderungen, die den Dissoziationsprozess näher beschreiben. Die Untersuchungen zeigen, daß die Stabilität der Verbindungen mit anwachsender Alkalimetall-Kationengröße zunimmt.

     

Synthesis, structure, and ionic conductivity of Na5Li3Ti2S8

The compound Na₅Li₃Ti₂S₈ has been synthesized by the reaction of Ti with a Na/Li/S flux at 723 K. Na₅Li₃Ti₂S₈ crystallizes in a new structure type with four formula units in space group C2/c of the monoclinic system. The structure contains three crystallographically independent Na⁺ cations and two crystallographically independent Li⁺ cations. Na₅Li₃Ti₂S₈ possesses a channel structure that features two-dimensional layers built from Li(1)S₄ and TiS₄ tetrahedra. The layers, which are stacked along c, comprise eight-membered rings and sixteen-membered rings. Na(3)⁺ cations are located between the eight-membered rings and Na(1)⁺, Na(2)⁺, and Li(2)⁺ cations are located between the sixteen-membered rings. These cations are each octahedrally coordinated by six S²⁻ anions. The ionic conductivity σ_T of Na₅Li₃Ti₂S₈ ranges from 8.8×10⁻⁶ S/cm at 303 K to 3.8×10⁻⁴ S/cm at 483 K. The activation energy E_a is 0.40 eV.     

Sodium‐ and Potassium‐Hydrate Melts Containing Asymmetric Imide Anions for High‐Voltage Aqueous Batteries

Aqueous Na‐ or K‐ion batteries could virtually eliminate the safety and cost concerns raised from Li‐ion batteries, but their widespread applications have generally suffered from narrow electrochemical potential window (ca. 1.23 V) of aqueous electrolytes that leads to low energy density. Herein, by exploring optimized eutectic systems of Na and K salts with asymmetric imide anions, we discovered, for the first time, room‐temperature hydrate melts for Na and K systems, which are the second and third alkali metal hydrate melts reported since the first discovery of Li hydrate melt by our group in 2016. The newly discovered Na‐ and K‐ hydrate melts could significantly extend the potential window up to 2.7 and 2.5 V (at Pt electrode), respectively, owing to the merit that almost all water molecules participate in the Na⁺ or K⁺ hydration shells. As a proof‐of‐concept, a prototype Na₃V₂(PO₄)₂F₃|NaTi₂(PO₄)₃ aqueous Na‐ion full‐cell with the Na‐hydrate‐melt electrolyte delivers an average discharge voltage of 1.75 V, that is among the highest value ever reported for all aqueous Na‐ion batteries.