Versatile 2‐aminothiazoles,building blocks for highly functionalised heterocycles

The reactions of quantitatively available 4‐phenyl‐ and 4‐(4‐antipyrinyl)‐2‐aminothiazole [“4‐antipyrinyl‐” is used as a short‐term for “4‐(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1‐H‐pyrazol‐4yl)‐”] with chloroacetyl chloride, acetic anhydride, ethyl cyanoacetate and carbon disulphide are reported. The products are transformed further by Knoevenagel condensations and coupling reactions with aromatic diazonium salts. The latter occur both at the thiazole ring and at the active methylene sites. The tautomerism of these products is studied on the basis of density functional theory calculations at the B3LYP/6‐31G* level.     

An investigation of the stored energy and thermal stability in a Cu–Ni–Si alloy processed by high-pressure torsion

ABSTRACT

The stored energy and activation energy for recrystallization were investigated for a Cu-Ni-Si alloy after high-pressure torsion processing for N?=?½, 1, 5 and 10 turns at room temperature. The contributions of geometrically necessary dislocations (GNDs), statistically stored dislocations (SSDs) and vacancies to the stored energy were calculated through the Vickers microhardness measurements, kernel average misorientation (KAM) measurements and an analysis by differential scanning calorimetry (DSC). The results show that the total stored energy decreases rapidly after equivalent strain of ε_eq?～?9 and then saturates through ε_eq?～?86 at ～70 J/mol. Concurrently, the local stored energy in GNDs and SSDs was found to depend strongly on the radial distance from the centre of the disc and increase with increasing equivalent strain at ε_eq?～?16 and saturate with further straining. Accordingly, the results indicate that the GNDs and vacancies are responsible for the high stored energy in the initial stage of deformation at equivalent strain range of ε_eq?=?8.6–16 and thereafter their contribution decreases slightly due to the occurrence of dynamic recrystallization and the formation of fine grains. At the same time, the contribution of the SSDs is similar to that of the GNDs only in high strain deformation as at ε_eq?=?49.3 to accommodate the deformation process. An activation energy for recrystallization was estimated in the range of ～?89.7–98.7 kJ/mol, thereby suggesting poor thermal stability.     

Detailed comparison between probe density measurements of glow discharge in argon and in helium

In this article we shall look a bit more closely at some of the fundamental plasma parameters obtained by a cylindrical Langmuir probe within low-pressure electrical gas discharge plasma. The presented measurements were made in argon and in helium glow discharge plasmas. We are mainly concerned with the densities of the charged particles (electrons and ions) within the plasma and the effect of the discharge conditions upon them. The electron density is calculated from the electron current at the space potential and from the integration over the EEDF. The ion density is calculated by using the OML collisionless theory. The parameterization of Laframboise's numerical results is also used for the ion density calculation. In the range of our experimental conditions the results of plasma density, for both gases, tend to show that the ion densities measured with the OML and Laframboise theories exceeds the measured electron densities. The results also show that the plasma electron and ion densities increased with both discharge power and gas pressure.     

CO adsorption on Ni, Pd, Cu and Ag deposited on MgO, CaO, SrO and BaO: Density functional calculations

The adsorption properties of CO molecules adsorbed on Ni, Pd, Cu and Ag atoms deposited on O²⁻, F and F⁺ sites of MgO, CaO, SrO and BaO terrace surfaces have been studied by means of density functional calculations and embedded cluster model. The examined clusters were embedded in the simulated Coulomb fields that closely approximate the Madelung fields of the host surfaces. The adsorption properties of CO have been analyzed with reference to the basicity of the oxide support, bond order conservation energy, pairwise and non-pairwise additivity, associative adsorption, electrostatic potentials, and orbital interactions. CO adsorption on an oxide support is drastically enhanced when CO is adsorbed on a metal deposited on this support. A dramatic change is found, and explained, when one compares the CO binding energy to O²⁻ and F sites. The formation of a strong bond at the support-metal interface has a considerable consequence on the metal-CO binding energy. The binding of CO is dominated by the metal-CO pairwise additive term, and the non-additivity term increases with increasing the basicity of the support. While the classical contributions to the electrostatic interactions are quite similar for the deposited metals, they are quite dissimilar when going from defect-free to defect-containing surfaces. The adsorption properties correlate linearly with the basicity and energy gaps of the oxide support where the electrostatic potential generated by the oxide modifies the physical and chemical properties of the adsorbed metal and therefore its reactivity versus the CO adsorbate.     

Classical Benzotriazole‐Mediated α‐Aminoalkylations of Alkynes: Synthesis and Characterization of Alk‐2‐yn‐1‐amines as Amphiphilic Materials

Reactions of readily available and stable benzotriazolemethanamines 1a – l , obtained from aldehydes and secondary amines (Scheme 2), gave the expected alk‐2‐yn‐1‐amines 3a – t (Scheme 3). The amphiphilic character of the synthesized products was responsible for physicochemical measurements. Specific aggregation properties of the obtained compounds make them useful as electroactive materials in the Langmuir–Blodgett technique.     

Synthesis of new 2‐ferrocenyl‐5‐fluoro‐6‐(4‐substituted‐1‐piperazinyl)‐1H‐benzimidazoles of potential biological interest

New substituted 2‐ferrocenylbenzimidazole derivatives are prepared by the oxidation of corresponding Schiff's bases in situ, generated from corresponding 1,2‐diamino‐4‐fluoro‐5‐(1‐piperazinyl)benzenes and 2‐ferrocenecarboxaldehyde using nitrobenzene.     

Continuation and maximal regularity of fractional-order evolution equation

The Cauchy problem of the homogeneous fractional-order evolution equation and evolutionary integral equation have been considered in [J. Fract. Calc. 7 (1995) 89] and [Korean J. Comput. Appl. Math. 9 (2002) 525]. The existence and uniqueness of the solution have been proved and the continuation of the solution and its fractional order derivative has been proved. Here we study the maximal regularity, continuation and some other properties of the Cauchy problem of the non-homogeneous fractional order evolution equation.     

Terahertz emission from collapsing field domains during switching of a gallium arsenide bipolar transistor

Broadband pulsed THz emission with peak power in the sub-mW range has been observed experimentally during avalanche switching in a gallium arsenide bipolar junction transistor at room temperature, while significantly higher total generated power is predicted in simulations. The emission is attributed to very fast oscillations in the conductivity current across the switching channels, which appear as a result of temporal evolution of the field domains generated in highly dense electron-hole plasma. This plasma is formed in turn by powerful impact ionization in multiple field domains of ultrahigh amplitude.     

Linear solvation energy correlation of the solvatochromic response of amino acid functionalized chromophores

Solvatochromism of the long wavelength band in the electronic absorption spectra of N-(4-nitrophenyl)-L-proline, NLP, N-(4-nitrophenyl)-D-proline, NDP, and N-(4-nitro-phenyl)-trans-4-hydroxy-L-proline, NHP, was studied and quantitatively described with Kamlet-Taft solvent polarity parameters. To evaluate the environmental effects for NLP, NDP, and NHP, the UV-vis spectroscopic behavior of these compounds was also investigated as pure crystals, as a guest in 2,6-O-dimethyl-beta-cyclodextrin, and also when adsorbed on Aerosil 300 silica particles from nonhydrogen-bond accepting solvents. Excellent Kamlet-Taft solvatochromic correlations were established for the three compounds in most solvents. Multiparameter correlations show the existence of specific solute-solvent interactions. A strong positive solvatochromic behavior was found for these compounds, indicating that their dipole moments were higher in the excited singlet state than in the ground state.