The Enhancement of the Formation of Wells–Dawson-Type Polyoxometalates by the Addition of High Concentrations of LiCl

Wells–Dawson-type polyoxometalates are formed by heating an acidic Mo(VI) or W(VI) solution containing significantly higher concentrations of hetero ions, P(V) or As(V), than the ideal molar ratio [M]/[X] = 1/9 (M = Mo, W; X = P, As). Most of the phosphate and arsenate remains unreacted in the reaction mixture. These reaction conditions are unusual, even though more reagents than the stoichiometric amounts are frequently needed to obtain complete reactions. In the present study, the replacement of a large amount of unreacted hetero ions containing salts by normal ions (salts) was investigated. The formation of Wells–Dawson-type polyoxometalates, [X₂M₁₈O₆₂]^6? (X = P, As; M = Mo, W), in the presence of LiCl and NaCl was investigated by Raman spectroscopy and ³¹P NMR in aqueous solution. The addition of LiCl enhanced the formation of Wells–Dawson-type polyoxometalates, which formed under solution conditions close to the ideal molar ratio [M]/[X] = 1/9.     

Theoretical Study on the Structures and Isomerization of Germylenoid GeH_2LiCl

Using geometrical optimization and DFT method at the B3LYP/6-311++G (3df,3pd) level, four equilibrium geometries and one transition state of GeH2LiCl were identified, and the structures at the MP2/6-311++G(3df,3pd) level were calculated simultaneously. We also studied the solvent effects on the structures of Germylenoid GeH2LiCl at the B3LYP/6-311++G (3df,3pd) level. The two more stable forms are suggested to be the p-complex and three-membered ring. The vibrational frequencies and infrared intensities were computed at the B3LYP/6-311++G (3df,3pd) level.     

Investigation of the evaporation of rare earth chlorides in a LiCl–KCl molten salt

Uranium dendrites which were deposited at a solid cathode of an electrorefiner contained a certain amount of salts. These salts should be removed for the recovery of pure metal using a cathode processor. In the uranium deposits from the electrorefining process, there are actinide chlorides and rare earth chlorides in addition to uranium chloride in the LiCl–KCl eutectic salt. The evaporation behaviors of the actinides and rare earth chlorides in the salts should be investigated for the removal of salts in the deposits. Experiments on the salt evaporation of rare earth chlorides in a LiCl–KCl eutectic salt were carried out. Though the vapor pressures of the rare earth chlorides were lower than those of the LiCl and KCl, the rare earth chlorides were co-evaporized with the LiCl–KCl eutectic salt. The Hertz–Langmuir relation was applied for this evaporation, and also the evaporation rates of the salt were obtained. The co-evaporation of the rare earth chlorides and LiCl–KCl eutectic were also discussed.     

Solutions of cellulose in DMAc + LiCl: migration of the solute in an electrical field

For solutions of cellulose (Solucell, M_w=230 kg mol^–1) in the mixed solvent DMAc (N,N-dimethylacetamide) + LiCl, it is demonstrated by means of an electrolysis cell, subdivided into six compartments, that cellulose migrates to the anode. This observation is interpreted in terms of a field-induced opening of associations between the [DMAc]_xLi⁺ complex and the [cellulose]Cl^– complex. This understanding is corroborated by the observed changes in the positions of the menisci in the electrode compartments of the electrolysis cell. Contrary to expectations, the rate of cellulose transport does not depend on its molar mass, at least under the present conditions.     

Regioselective functionalization of the thiazole scaffold using TMPMgCl·LiCl and TMP2Zn·2MgCl2·2LiCl

A general method for the synthesis of 2,4,5-trisubstituted thiazoles has been developed. Starting from commercially available 2-bromothiazole, successive metalations using TMPMgCl·LiCl or TMP(2)Zn·2MgCl(2)·2LiCl lead to the corresponding magnesated or zincated thiazoles which readily react with various electrophiles providing highly functionalized thiazoles.     

Thermogravimetric study of the dehydration reaction of LiCl·H<Subscript>2</Subscript>O

The dehydration of LiCl·H₂O was studied under inert helium atmosphere by DTA/TG for different heating rates. The dehydration of LiCl·H₂O proceeds through a two step reaction between 99–110 and 160–186°C, respectively. It leads to the formation of LiCl·0.5H₂O as intermediate compound. The proposed mechanism is: and Based on the temperature peak of the DTA signals the activation energies of the two reactions were determined to be 240 kJ mol⁻¹ (step 1) and 137 kJ mol⁻¹ (step 2), respectively.     

Dismutation of divalent americium induced by the addition of fluoride anion to a LiCl–KCl eutectic at 743 K

The three oxidation states of americium (III), (II) and (0) are stable in a molten LiCl–KCl eutectic at 743 K. Addition of fluoride anion to the melt led to the disproportionation of Am²⁺ into Am³⁺ and Am. The effect of fluoride additions was monitored with potentiometric and cyclic voltammetry methods and the relative cumulative formation constants of the Am(III) fluoro-complexes determined.     

Reaction characteristics of cellulose in the LiCl/1,3‐dimethyl‐2‐imidazolidinone solvent system

In order to elucidate the nature of the LiCl/1,3dimethy2imidazolidinone (DMI) solvent system as one of the homogeneous reaction media of cellulose, cellulose acetate (CA) and Omethylcellulose (MC) were prepared using this solvent system, and the distribution of substituents within anhydroglucose units was examined by ¹³CNMR. It was found that (i) homogeneous cellulose solutions can be easily prepared by heating 2, 5–12 and 100 parts of weight of cellulose, LiCl, and DMI, respectively, and (ii) the relative reactivity of hydroxyl groups is in the order C6 > C2 > C3 for both CA and MC. A remarkable feature of this solvent system is that the reaction efficiency in etherification is very high compared with other homogeneous solvent systems.     

PTC and organic bases–LiCl assisted alkylation of imidazolidinone–glycine iminic derivatives for the asymmetric synthesis of α-amino acids

Iminic derivatives of (4R,5S)-1,5-dimethyl-4-phenylimidazolidin-2-one and glycine 4 have been highly diastereoselectively alkylated with activated alkyl halides or electrophilic olefins either under PTC conditions or in the presence of the strong organic bases DBU or BEMP at −20°C in the presence of LiCl. Hydrolysis of the alkylated imino imides gave (S)-α-amino acids with recovery of the imidazolidinone chiral auxiliary.     

Underpotential deposition of Li in a molten LiCl–Li2O electrolyte for the electrochemical reduction of U from uranium oxides

Reactive metal oxides are conventionally reduced to metal by metallothermic reduction. This paper presents on the efficient reduction method based on the electrochemical reaction in a molten LiCl–Li₂O electrolyte at 650 °C. An underpotential deposition of Li on uranium oxides was observed that enabled the mass electrochemical reduction of U₃O₈ to U. An advantage of using in-situ generated Li as a reductant is that a high-speed electrochemical reduction could be achieved with a wider operating voltage window when compared to a direct electrochemical reduction.     

Electrochemical separation of uranium and cerium in molten LiCl–KCl

The electrochemical separation of uranium from cerium in LiCl–KCl eutectic and the electrochemical behavior of Ce(III) were studied. According to the cyclic voltammogram of Ce(III) and the former result of U(III), electrodeposition potential was determined at ?1.65 V (vs Ag/AgCl). The uranium metal was successfully deposited and separated from cerium. The morphology of deposit and cross section of electrode were investigated by SEM, firstly uranium deposit alloys with stainless steel and forms a thin transition layer, and secondly the uranium metal layer grows from the transition layer. The separation factors of uranium/cerium on different recovery ratios were determined through a series of steps. It was found that the content of cerium in the deposit and separation factors declined with increasing the initial concentration of U³⁺ in molten salts; the separation factors remained stable at around 20 in different uranium recovery ratios.     

Magnesiation of N-Heterocycles Using i-PrMgCl · LiCl and Catalytic Diisopropylamine

The direct magnesiation of various N-heterocyclic compounds with i-PrMgCl · LiCl and catalytic diisopropylamine allows for preparation of 2-substituted pyrroles, imidazole, indoles, and benzimidazoles, in moderate to good yields. The magnesiated substrates canreadily undergo a Kumada-type coupling with iodo-aryls in the presence of catalytic Pd(PPh₃)₄.     

Solution properties of celluloses from different biological origins in LiCl · DMAc

Differences in the solution properties of cellulose in 8%LiCl·DMAc (dimethyl acetamide) were investigated usingcelluloses from different origins. The latter included plants (dissolving pulp(DP), cotton linters (CC), and kraft pulp), bacteria (Acetobacterxylinum, BC), and marine animals (tunicin fromHalocynthia). The celluloses from plants and bacteriaformed LiCl·DMAc solutions that were isotropic andanisotropic, respectively; and the animal cellulose was insoluble. The weightaverage molecular weights, M_w, of DP, CC and BC were found to be98.2×10⁴,170×10⁴ and192×10⁴, respectively. The solutionviscositieswere proportional to c (c; polymer concentration) in thedilute and semi-dilute regions, where the exponent was 1 for allsamplesin the dilute region; in the semi-dilute region, it was 4 for the DP and CCsolutions and 3 for the BC solution. Molecular weight differences werecompensated by plotting the viscosity against cM_w orc[] (where [] is the limiting viscosity number).The difference in viscosity behavior at elevated solutionconcentration indicates that the cellulose molecules from DP and CC behave asflexible polymer chains and those of BC as rod-like ones.These results suggest that differences in molecular structure andproperties exist between celluloses from different sources, and that thesedifferences relate to the mechanism or the type of the intermolecularinteraction between the celluloses of plants (DP and CC) and those of bacteria(BC).     

Construction of the Skeleton of Phthalascidin, Mechanism of the Formation of the Key Tricyclic Lactam Intermediate

Phthalascidin is a structurally simplified version of Et-743, which is a potent anti-tumor marine natural product isolated from Ecteinascidia turbinata. Its antiproliferative activity is greater than that of the agents taxol, camptothecin, adriamycin, mitomycin C, cisplatin, bleomycin, and etoposide by 1-3 orders of magnitude. An elegant synthesis of Et-743 and phthalascidin has been reported by E. J. Corey and co-workers1,2. As part of our continuing program, we have also engaged in dev…     

Studies of the dissociation and the protonation of TB-chlorosulphophenol

The dissociation constant of each step for TB-chlorosulphophenol has been determined by potentiometric method, and the thermodynamic constants, △G°, △H° and △S°, of the dissociation process have been calculated. The protonation constants were measured by the spectrophotometric method. The pH values of various forms of anions of the chromogenic reagent at their concentrations were also calculated.     

Synthesis of two peptides of α-bungarotoxin and the participation of the amino acid residue Trp-28 of the neurotoxin in the antigenicity of the molecule

Using the method of solid-phase peptide synthesis, two peptides have been synthesized, one of which corresponds to the central ring structure of -bungarotoxin (-BTX), while the second has in position 28 a Gly residue in place of the Trp in the first peptide, and their interrelationship with antitoxin antibodies has been investigated. It has been shown that the amino acid residue Trp-28 of -BTX, which is the contact residue in binding with the acetylcholine receptor, also participates directly in binding with the active centers of antibodies to -BTX.Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 628–631, July–August, 1997.     

Pd-catalyzed α-arylation of nitriles and esters and γ-arylation of unsaturated nitriles with TMPZnCl·LiCl

Using TMPZnCl·LiCl as a kinetically highly active base, nitriles and esters undergo a Pd-catalyzed α-arylation under mild conditions. Remarkably, in the case of α,β- or β,γ-unsaturated nitriles, a regioselective γ-arylation or a γ-alkenylation is observed.     

Determination of the equilibrium melting point of the β-form of polypropylene

The melting behavior of the -form of isotactic polypropylene (-iPP) was investigated as a function of crystallization time and temperature. Calcium suberate, a selective -nucleating agent was used to produce samples that consist entirely of -form i-PP. The experimental melting points were recorded at different crystallization times and were extrapolated to the start of the crystallization process in order to eliminate the effect of lamellar thickening. Using the non-linear Hoffman—Weeks approach to correlate these extrapolated experimental melting temperatures with the corresponding crystallization temperatures, an equilibrium melting point of 209°C was obtained for -iPP. The equilibrium melting point estimated through the non-linear Hoffman—Weeks analysis is about 30°C higher than that (T _m ⁰=177°C) obtained on the basis of the linear extrapolation. These results are consistent with earlier claims that a linear extrapolation of T _m–T _c data leads to an underestimation of the equilibrium melting point. The results obtained for -iPP exemplify the importance of accounting for both the isothermal lamellar thickening effects and the non-linearity in the T _m–T _c correlation, when the determination of an equilibrium melting point is carried out using a procedure based on the predictions of the Lauritzen—Hoffman secondary nucleation theory.This revised version was published online in November 2005 with corrections to the Cover Date.