Quantum-chemical simulation of interaction of polycaproamide with a lithium chloride solution in dimethylacetamide

Quantum-chemical calculations of interaction between lithium chloride and dimethylacetamide (DMAc) and between the polycaproamide model fragment CH₃NHCO(CH₂)₅NHCOCH₃ and a lithium chloride solution in DMAc were performed. The software package GAMESS with the MINI basis set was used in the calculations. Models of the solution included 2 LiCl molecules and 8–16 DMAc molecules. All of these models suggest three potential energy minimums corresponding to three stable structures that differ in the relative arrangement of lithium and chloride ions. A decrease in the amount of solvent in the system leads to transition from Li⁺(DMAc)₄Cl^- to Li⁺...Cl^-(DMAc)₃ and then to the (LiCl)₂(DMAc)₂ species, which crystallizes to form the 1: 1 crystal solvate. The mechanism of dissolution of polycaproamide in DMAc containing lithium chloride was refined.     

Thermokinetic characteristics of lithium chloride

The characterisation of the ionic compound of lithium chloride, LiCl, through XRD, SEM, DSC, TG, DTG and TG-MS analysis is reported. The results show that nominally anhydrous LiCl particles can readily absorb water from the ambient atmosphere to form a surface layer of lithium chloride mono-hydrate, LiCl·H₂O. Solid surface-hydrated LiCl is de-dehydrated via a two-stage mechanism at low heating rates and via a single-stage mechanism at high heating rates. Molten LiCl exhibits substantial evaporation at temperatures below its nominal boiling point, with the rate of evaporation increasing significantly before complete evaporation occurs. The melting process of de-hydrated LiCl is marginally affected by the heating rate; whilst the evaporation process is strongly affected by the heating rate and also dependent on the quantity of material used and the flow rate of the gas passed over it. Heating of surface-hydrated LiCl up to the point of evaporation under a flow of argon and under a flow of ambient air gives identical results, proposing the possibility of performing LiCl-based processes in an air environment. The enthalpies and activation energies for the processes of surface de-hydration, melting, and high-temperature evaporation are determined. The results are consistent with the following thermal phase evolution:

$ [{\text{LiCl + LiCl}} \cdot {\text{H}}_{{\text{2}}} {\text{O}}]_{{{\text{solid}}}} \to [{\text{LiCl}}]_{{{\text{solid}}}} \to [{\text{LiCl}}]_{{{\text{liquid}}}} \mathop\rightarrow\limits^{{{{\text{H}}_{{\text{2}}} {\text{O}} \downarrow {\text{ HCl}} \uparrow}}}[{\text{LiCl-LiOH}}]_{{{\text{liquid}}}} \mathop\rightarrow\limits^{{{{\text{H}}_{{\text{2}}} {\text{O}} \uparrow}}}[{\text{LiCl-Li}}_{{\text{2}}} {\text{O}}]_{{{\text{liquid}}}} \to {\text{Gas}} $

     

Ternary diffusion coefficients of diethylene glycol and lithium chloride in aqueous solutions containing diethylene glycol and lithium chloride

In this work, ternary diffusion coefficients of diethylene glycol and lithium chloride in aqueous solutions containing diethylene glycol and lithium chloride were reported for temperatures (303.2, 308.2, and 313.2 K) using the Taylor dispersion method. The investigated ternaries contained total glycol–salt concentrations of 10, 15, and 20 wt%. The main diffusion coefficients (D₁₁ and D₂₂) and the cross-diffusion coefficients (D₁₂ and D₂₁) were discussed as function of temperature and concentration. A modified equation originally proposed by Batchelor [1] for mixture of hard spheres in a continuum solvent was used to correlate the present diffusion coefficient data and the results are satisfactory.     

Kinetics and mechanism of benzyl chloride reaction with zinc in dimethylacetamide

Oxidative dissolution of zinc in the system of benzyl chloride-dimethylacetamide was investigated. The reaction stereochemistry as well as intermediates and reaction products formed were studied. The kinetic and thermodynamic parameters of the process were measured. The process was shown to follow the Langmuir-Hinshelwood mechanism with the formation of benzyl radicals and mono-solvated organozinc compound on the zinc surface. The components of mixture are adsorbed at various sites of the zinc surface, while recombination and the isomerization of the benzyl radicals occurs in solution.     

Electrochemical characteristics of the blended polymer electrolytes containing lithium salts

Blend-based polymer electrolytes composed of poly(ethylene oxide), poly(oligo[oxyethylene]oxysebacoyl), and lithium salts have been prepared. These polymer electrolytes have been investigated in terms of ionic conductivity, transport number, and interfacial characteristics of the lithium electrode in contact with the polymer electrolyte. The influences of the blend composition, the salt used, and its concentration on the electrochemical behavior were studied. © 1996 John Wiley & Sons, Inc.     

Higher hydrates of lithium chloride,lithium bromide and lithium iodide

For lithium halides, LiX (X = Cl, Br and I), hydrates with a water content of 1, 2, 3 and 5 moles of water per formula unit are known as phases in aqueous solid–liquid equilibria. The crystal structures of the monohydrates of LiCl and LiBr are known, but no crystal structures have been reported so far for the higher hydrates, apart from LiI·3H₂O. In this study, the crystal structures of the di‐ and trihydrates of lithium chloride, lithium bromide and lithium iodide, and the pentahydrates of lithium chloride and lithium bromide have been determined. In each hydrate, the lithium cation is coordinated octahedrally. The dihydrates crystallize in the NaCl·2H₂O or NaI·2H₂O type structure. Surprisingly, in the tri‐ and pentahydrates of LiCl and LiBr, one water molecule per Li⁺ ion remains uncoordinated. For LiI·3H₂O, the LiClO₄·3H₂O structure type was confirmed and the H‐atom positions have been fixed. The hydrogen‐bond networks in the various structures are discussed in detail. Contrary to the monohydrates, the structures of the higher hydrates show no disorder.     

Chronopotentiometry in fused lithium chloride-potassium chloride

Previous work in the application of chronopotentiometry in aqueous and fused salt media has been reviewed. This investigation describes the application of this principle to the reduction of cadmium, cobalt, lead and thallium ions in a fused eutectic mixture of potassium, chloride and lithium. chloride at 450°C. Platinum microelectrodes of different areas and geometry were used. The transition time was limited to the order of 0.2 to 0.7 sec using oscillographic recording.It was found that so long as the dimensions of the electrode were considerably greater than the thickness of the diffusion, layer, linear diffusion theory was obeyed. The transition time constants for cadmium, cobalt, lead and thallium ions were found to be 0.83± 0.02, 0.90 ± 0.03, 0.95 ± 0.04, and 0.59 ± 0.02.10³ amp cm sec$\text{1}\text{2}$ per mole, respectively. The diffusion coefficients of these ions were calculated to be 2.08, 2.42, 2.18 and 3.88.IO^-5 cm² sec^-1, respectively.     

Decomposition into dimethylacetamide hydroperoxide radicals in dimethylacetamide as the medium

Conclusions N, N-Dimethylacetamide hydroperoxide thermally decomposes into free radicals in N,N-dimethylacetamide as the medium at a rate that is directly proportional to the hydroperoxide concentration and inversely proportional to the amide concentration. A scheme was proposed and the effective initiation rate constant was determined in the range 84–115°.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 965–967, April, 1978.The authors express their gratitude to N. N. Pozdeeva for assistance in the work, and to V. T. Varlamov for taking the IR spectra.     

Conformational characteristics of polystyrene

Conformational energies, computed with a forcefield including coulombic interactions and a simple accounting for the effects of solvent, of meso and racemic 2,4-diphenylpentane as model substances of polystyrene have been computed as functions of the skeletal torsion angles and the phenyl torsion angles. The relatively high energies of the ḡ conformations rendered these states negligible and no minimum was found in the meso-tt domain. Three minima for the meso diad (gt, tg, gg) and four minima for the racemo diad (tt, tg, gt, gg) are relevant. A two-state rotational isomeric state model is applicable with states at φ_t = 5°C and φ_g = 110° for both meso and racemo diads. Statistical weight matrices have been derived and values predicted for the characteristic ratio, the fractions of 2,4-diphenylpentane and 2,4,6-triphenylheptane at stereo-chemical equilibrium and the vicinal NMR coupling constants are found to be consistent with experimental results.     

Electrochemical investigation of lithium intercalation into graphite from molten lithium chloride

Lithium reduction at a graphite electrode in molten lithium chloride was studied at temperatures from 650 to 900 °C using cyclic voltammetry and chronoamperometry. It was found that, during cathodic polarization, lithium intercalation into graphite occurred before deposition of metallic lithium started. This process was confirmed to be rate-controlled by the diffusion of lithium in the graphite. When the cathodic polarization potential was more negative than that for metallic lithium deposition, exfoliation of graphite particles from the electrode surface was observed. This was caused by fast and excessive accumulation of lithium intercalated into the graphite, which produced mechanical stress too high for the graphite matrix to accommodate. The erosion process was abated once the graphite surface was covered by a continuous layer of liquid lithium. These results are of relevance to the mechanism of carbon nanotube and nanoparticle formation by electrochemical synthesis in molten lithium chloride.     

Solvoluminescence from γ-irradiated lithium chloride

Solvoluminescence /SL/ of -irradiated LiCl crystals have been studied in some organic solvents. The SL emission spectra of LiCl crystals were recorded in N-methyl acetamide, nitrobenzene, cyclohexanol, cyclohexanone and pure water. The total SL intensity of LiCl in various organic solvents was found to vary with the type and nature of the solvent. The results are explained on the basis of the electron-scavenging effect and complexing abilities of the solvents.     

Induced free-radical chain decomposition of dimethylacetamide hydroper oxide in dimethylacetamide as the medium

Conclusions The thermal gross decomposition of dimethylacetamide hydroperoxide (ROOH) in dimethylacetamide (RH) as the medium proceeds in harmony with the equation: W_p=k_ind [ROOH]₀ ^m/[RH]₀ ⁿ, where m=1.5–2; n=2–0.5. Alkyl radicals with a chain length of 195–3 units are mainly responsible for the induced decomposition. We determined the ratio between the molecular and radical directions of the decomposition and k_ind in the range 80–132°.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 967–970, April, 1978.     

The passivation phenomenon of rhodium in fused lithium chloride + potassium chloride eutectic

The passivation phenomenon of rhodium was investigated in fused lithium chloride + potassium chloride eutectic by means of the potential sweep method. The current-potential curve obtained showed a typical N-shaped negative impedance. An anodic current rise was observed at +0.3 V vs. Ag/AgCl (0.1). The current was controlled by mass transfer and was ascribed to the dissolution of rhodium into rhodium(III) ions. The observed Flade potential was +0.45 V at 400°C. The passivation was found to occur due to the precipitation of supersaturated Rh(III) chloride onto the electrode surface. The residual current for the passivation was fairly high and the current increased significantly as the temperature was made higher. The dissolution current of rhodium into Rh(III) ions decreased with increase in the concentration of oxide ions. The fact revealed that the rhodium was passivated preferentially due to the formation of Rh(III) oxide. The residual current of the oxide passivation film was low enough. The thickness of the film corresponded to 10–20 atomic layers of the parent metal. Rhodium showed another anomalous passivation due to the formation of oxide. The oxide was formed at ?0.3 V and was reduced at ?0.6 V. It was considered to be a low valence rhodium oxide, RhO or Rh₂O. Rhodium was found to have a low chlorine overpotential. However, it was redissolved at the chlorine evolution region, above +1.25 V. The dissolution was not prevented even in the oxide ion containing melts.