A concise approach to CF3-containing furan-3-ones, (bis)pyrazoles from novel fluorinated building blocks based on 2,3-butanedione

1,1,1-Trifluoro-4,5,5-trimethoxyhex-3-en-2-one and lithium (2Z)-1,1,1-trifluoro-5,5-dialkoxy-4-oxohex-2-en-2-olate were synthesized for the first time via direct trifluoroacetylation of 2,3-butanedione acetal derivatives. A simple and effective approach to acetal or acyl substituted CF₃-pyrazoles, 5,5′-bis(trifluoromethyl)-3,3′-bipyrazole, and, to 5-trifluoromethylfuran-3-ones is presented.     

Hydroelastic stability of multi-plate structures interacting with flowing fluid

The paper is concerned with the finite-element analysis of natural vibrations and hydroelastic stability of two parallel plates interacting with liquid. The influence of the fluid layer thickness on the eigenfrequencies, vibration modes and hydroelastic stability boundary are estimated based on the results of numerical solution of some example problems. The numerical investigation substantiates the existence of various instability modes, the onset of which depends on the combinations of kinematic boundary conditions specified at the plate ends. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Combination of radon and stable isotope analysis as a tool for decision support concerning the remediation of NAPL-contaminated sites

The non-aqueous phase-liquid (NAPL)-contaminated aquifer at a major refinery site in Mexico was investigated. Owing to the depth of the contaminated aquifer section (NAPL source zone) of over 100 m below the surface, the actual aquifer material was not accessible for sampling. Information on the residual NAPL contamination of the aquifer could only be obtained indirectly by analysing groundwater samples from a few wells available at the site. To tackle the problem, an approach alternative to conventional groundwater analysis for dissolved NAPL was chosen. For evaluating the recent contamination and estimating its probable future development, the radioisotope radon-222 and the stable isotopes 13C, 34S and 18O were used as naturally occurring contamination tracers and process indicators. Radon was used as partitioning tracer for the approximate localization and semi-quantitative assessment of the NAPL source zone. The stable isotopes were used as indicators for naturally occurring biodegradation processes, which might potentially be implemented into future remediation schemes.     

Synthesis and antiherpetic activity of novel purine conjugates with 7,8-difluoro-3-methyl-3,4-dihydro-2H-1,4-benzoxazine

Chemistry of Heterocyclic Compounds - A method for the synthesis of novel purine conjugates with 7,8-difluoro-3-methyl-3,4-dihydro-2H-1,4-benzoxazine containing fragments of ω-amino acids with...     

Novel purine conjugates with N-heterocycles: synthesis and anti-influenza activity

Chemistry of Heterocyclic Compounds - A number of novel amides were synthesized by coupling of 6-[(9H-purin-6-yl)amino]hexanoic acid to heterocyclic amines. The antiviral activity of the obtained...     

Analysis of Non-innocence of Phosphaquinodimethane Ligands when Charge and Aromaticity Come into Play

Several phosphaquinodimethanes and their M(CO)₅ complexes (M=Cr, Mo, W) and model derivatives have been theoretically investigated regarding the quest of non-innocence. Computed structural and electronic properties of the P-Me/NH₂ substituted phosphaquinodimethanes and tungsten complexes revealed an interesting non-innocent ligand behaviour for the radical anion complexes with distonic ion character and a strong rearomatization of the middle phenyl ring. The latter was further probed taking also geometric aromaticity (HOMA) and quinoid distortion parameters (HOMQc) into account, as well as NICS(1). Furthermore, the effect of the P-substitution was investigated for real (or plausible) complexes and their free ligands focusing on the resulting aromaticity at the middle phenyl ring and vertical one-electron redox processes. The best picture of ligand engagement in redox changes was provided by representing NICS(1) values versus HOMA and the new geometric distortion parameter HOMQc8.     

Coercivity of Combined Boundary Integral Equations in High‐Frequency Scattering

We prove that the standard second‐kind integral equation formulation of the exterior Dirichlet problem for the Helmholtz equation is coercive (i.e., sign‐definite) for all smooth convex domains when the wavenumber k is sufficiently large. (This integral equation involves the so‐called combined potential, or combined field, operator.) This coercivity result yields k‐explicit error estimates when the integral equation is solved using the Galerkin method, regardless of the particular approximation space used (and thus these error estimates apply to several hybrid numerical‐asymptotic methods developed recently). Coercivity also gives k‐explicit bounds on the number of GMRES iterations needed to achieve a prescribed accuracy when the integral equation is solved using the Galerkin method with standard piecewise‐polynomial subspaces. The coercivity result is obtained by using identities for the Helmholtz equation originally introduced by Morawetz in her work on the local energy decay of solutions to the wave equation. © 2015 Wiley Periodicals, Inc.     

A Promising Thermodynamic Study of Hole Transport Materials to Develop Solar Cells: 1,3-Bis(N-carbazolyl)benzene and 1,4-Bis(diphenylamino)benzene

The thermochemical study of the 1,3-bis(N-carbazolyl)benzene (NCB) and 1,4-bis(diphenylamino)benzene (DAB) involved the combination of combustion calorimetric (CC) and thermogravimetric techniques. The molar heat capacities over the temperature range of (274.15 to 332.15) K, as well as the melting temperatures and enthalpies of fusion were measured for both compounds by differential scanning calorimetry (DSC). The standard molar enthalpies of formation in the crystalline phase were calculated from the values of combustion energy, which in turn were measured using a semi-micro combustion calorimeter. From the thermogravimetric analysis (TGA), the rate of mass loss as a function of the temperature was measured, which was then correlated with Langmuir’s equation to derive the vaporization enthalpies for both compounds. From the combination of experimental thermodynamic parameters, it was possible to derive the enthalpy of formation in the gaseous state of each of the title compounds. This parameter was also estimated from computational studies using the G3MP2B3 composite method. To prove the identity of the compounds, the ¹H and ¹³C spectra were determined by nuclear magnetic resonance (NMR), and the Raman spectra of the study compounds of this work were obtained.