Reaction of indazole and alkylpyrazoles with acetylene

The reaction of indazole and pyrazole and its alkyl-substituted derivatives with acetylene was studied. It was established that indazole and 3(5)-methylpyrazole form a mixture of vinyl isomers corresponding to their tautomeric forms under vinylation conditions. The ratios of the isomers of vinylindazoles in the reaction mixtures depend on the nature of the catalyst. The indazole isomers were separated by gas-liquid chromatography, and the 3(5)-methylpyrazole isomers were separated by vacuum fractionation. 1-Di(1-pyrazolyl)ethanes, the structure of which was confirmed by their PMR spectra, are also formed in the vinylation of pyrazoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1247–1251, September, 1976.     

Closing the Cycle as It Begins: Synthesis of ortho-Iodobiaryls via Catellani Reaction

Despite the advances in the field of carbon-halogen bond formation, the straightforward catalytic access to selectively functionalized iodoaryls remains a challenge. Here, we report a one-pot synthesis of ortho-iodobiaryls from aryl iodides and bromides by palladium/norbornene catalysis. This new example of Catellani reaction features the initial cleavage of a C(sp²)−I bond, followed by the key formation of a palladacycle through ortho C−H activation, the oxidative addition of an aryl bromide and the ultimate restoration of the C(sp²)−I bond. A large variety of valuable o-iodobiaryls has been synthesized in satisfactory to good yields and their derivatization have been described too. Beyond the synthetic utility of this transformation, a DFT study provides insights on the mechanism of the key reductive elimination step, which is driven by an original transmetallation between palladium(II)-halides complexes.     

Peculiarities of the electron energy spectrum in the Coulomb field of a superheavy nucleus

We consider the peculiarities of the electron energy spectrum in the Coulomb field of a superheavy nucleus and discuss the long history of an incorrect interpretation of this problem in the case of a pointlike nucleus and its current correct solution. We consider the spectral problem in the case of a regularized Coulomb potential. For some special regularizations, we derive an exact equation for the point spectrum in the energy interval (-m,m) and find some of its solutions numerically. We also derive an exact equation for charges yielding bound states with the energy E = -m; some call them supercritical charges. We show the existence of an infinite number of such charges. Their existence does not mean that the oneparticle relativistic quantum mechanics based on the Dirac Hamiltonian with the Coulomb field of such charges is mathematically inconsistent, although it is physically unacceptable because the spectrum of the Hamiltonian is unbounded from below. The question of constructing a consistent nonperturbative second-quantized theory remains open, and the consequences of the existence of supercritical charges from the standpoint of the possibility of constructing such a theory also remain unclear.     

Low-temperature phase formation in CaF<Subscript>2</Subscript>–HoF<Subscript>3</Subscript> system

Phase formation in CaF₂–HoF₃ system has been studied by coprecipitation followed by X-ray powder diffraction. Aqueous nitrate solutions have been used as initial substances, while hydrofluoric acid has been employed as fluorinating agent. Formation of hydrated nanophases: solid solution Ca_1–x Ho _x F_{2 + x} (х ≤ 0.1) and HoF3 has been revealed. Dehydration proceeds on heating to 600°C.     

Phase equilibria in systems of gallium sulfate with lithium or sodium sulfate

The phase diagrams of binary systems of gallium sulfate with lithium or sodium sulfate were studied for the first time. The Li₂SO₄–Ga₂(SO₄)₃ system is of the eutectic type. The coordinates of the eutectic are (548°C, 30 mol % Ga₂(SO₄)₃). The region of a solid solution based on the high-temperature modification α-Li₂SO₄ is small. In the Na₂SO₄–Ga₂(SO₄)₃ system, compound Na₃Ga(SO₄)₃ forms, which melts incongruently at 585°C. The coordinates of the eutectic are (538°C, 17 mol % Ga₂(SO₄)₃). The region of a solid solution based on α-Na₂SO₄ reaches 8 ± 1 mol % Ga₂(SO₄)₃. The X-ray powder diffraction pattern of Na₃Ga(SO₄)₃ was indexed in a tetragonal unit cell with the parameters a = 9.451(3) Å and c = 7.097(3) Å; the unit cell parameters for an aluminum-containing analog, Na₃Al(SO₄)₃, are a = 9.424(5) Å and c = 7.053(3) Å.     

Thermodynamic properties of methane hydrate in quartz powder

Using the experimental method of precision adiabatic calorimetry, the thermodynamic (equilibrium) properties of methane hydrate in quartz sand with a grain size of 90-100 microm have been studied in the temperature range of 260-290 K and at pressures up to 10 MPa. The equilibrium curves for the water-methane hydrate-gas and ice-methane hydrate-gas transitions, hydration number, latent heat of hydrate decomposition along the equilibrium three-phase curves, and the specific heat capacity of the hydrate have been obtained. It has been experimentally shown that the equilibrium three-phase curves of the methane hydrate in porous media are shifted to the lower temperature and high pressure with respect to the equilibrium curves of the bulk hydrate. In these experiments, we have found that the specific heat capacity of the hydrate, within the accuracy of our measurements, coincides with the heat capacity of ice. The latent heat of the hydrate dissociation for the ice-hydrate-gas transition is equal to 143 +/- 10 J/g, whereas, for the transition from hydrate to water and gas, the latent heat is 415 +/- 15 J/g. The hydration number has been evaluated in the different hydrate conditions and has been found to be equal to n = 6.16 +/- 0.06. In addition, the influence of the water saturation of the porous media and its distribution over the porous space on the measured parameters has been experimentally studied.     

Minimization of artifact protein aggregation using tetradecyl sulfate and hexadecyl sulfate in capillary gel electrophoresis under reducing conditions

In the biopharmaceutical industry, CE-SDS assesses the purity, heterogeneity, and stability of therapeutic proteins. However, for mAb-1 and mAb-2, typical CE-SDS under reducing conditions produced atypical protein peak profiles, which led to biased purity results, thus were not acceptable for biologics manufacturing. This bias was caused by the formation of method-induced higher molecular weight artifacts, the levels of which correlated with protein concentration. Here we show that adding sodium tetradecyl and hexadecyl sulfates to the sample and the sieving gel buffer solutions was required to prevent formation of aggregate artifacts and to maintain detergent:protein uniformity, suggesting their importance during the sample preparation steps of heat denaturation and subsequent cooling as well as during capillary migration. For these proteins, we show that this uniformity was likely due to the ability of these detergents to bind proteins with markedly higher affinities compared to SDS. “CE-SC_XS” methods (where CE-SC_XS is CGE using detergent composed of a sodium sulfate head group and a hydrocarbon tail, with “C_X” representing various tail lengths), were developed with a sodium tetradecyl sulfate sample buffer and a sodium hexadecyl sulfate containing sieving gel buffer that minimized artifacts and provided robust characterization and release results for mAb-1 and mAb-2.     

Describing of the properties of quadrupole states in a 94Mo nucleus with skyrme interaction

The influence of coupling between simple and complex configurations on the probabilities of E2 and M1 transitions between vibrational quadrupole states is investigated. The finite rank separable approximation for the Skyrme effective forces is used. Properties of the low-energy spectrum for quadrupole excitations in ⁹⁴Mo nucleus are considered.     

Coprecipitation from aqueous solutions to prepare binary fluorides

The synthesis of binary fluoride phases, specifically nanofluorides, by coprecipitation from aqueous solutions is considered in terms of phase equilibria. Phases have been precipitated in NaF-RF₃ systems (where R stands for a rare-earth element), MF₂-YF₃ systems (where M = Ca, Sr, Ba), BaF₂-ScF₃, and CaF₂-BaF₂ systems. In the MF₂-YF₃ systems, unordered metastable congruently soluble phases are precipitated instead of ordered fluorite-like phases. In the BaF₂-ScF₃ system, the congruently soluble compound Ba₃Sc₂F₁₂ is precipitated. In the NaF-RF₃ systems, incongruently soluble metastable phases with a fluorite-like structure (for R = Er, Lu, Y) and the gagarinite structure (NaGdF₄) are formed. In the CaF₂-BaF₂ system, intermediate phases have not been formed.     

Raman spectra and phase transitions in Rb<Subscript>2</Subscript>KInF<Subscript>6</Subscript> elpasolite

The Raman spectra of Rb₂KInF₆ elpasolite crystal have been studied in a wide temperature range, including two phase transitions: from the cubic phase to the tetragonal phase and then to the monoclinic phase. Several anomalies of internal modes of InF₆ octahedra and low-frequency lattice vibrations, which are related to the structural changes at the transition points, have been found and quantitatively analyzed. The results of a quantitative analysis of the temperature dependences of the parameters of spectral lines are in good agreement with the thermodynamic data on the phase transitions.