Sodium dithionite initiated addition of 1-bromo-1-chloro-2,2,2-trifluoroethane to allylaromatics: Facile synthesis of conjugated dienes substituted with terminal CF3 group

Sodium dithionite effectively promotes the addition of 1-bromo-1-chloro-2,2,2-trifluoroethane to the terminal double bond of allylbenzenes 1. The reactions proceeded in MeCN/H₂O to give a 3:1 mole ratio of diastereoisomers of 1-(2-bromo-4-chloro-5,5,5-trifluoropentyl)benzenes 2 as the main products together with small amounts of its reductive debromination products 3. Total yields of 2 and 3 were dependent on the nature of the aromatic ring substituents in 1. Treatment of adducts 2 with DBU in refluxing hexanes resulted in double dehydrohalogenation affording, in good yields, conjugated dienes 4 (1,1,1-trifluoro-5-phenyl-2,4-pentadienes) terminated with the CF₃ group at the one end and the phenyl group at the opposite end. These dienes were found to be sufficiently reactive to undergo Diels-Alder condensation with active dienophiles to give trifluoromethylated carbocycles. The reactions of CF₃CHClBr with allylheterocycles were less successful and lead to low yields of mixtures of hardly separable compounds or to polymeric resins.     

Lipophilicity characterization of new N-phenylamino-azaspiranes as potential anticonvulsant agents

The lipophilicity of a library of N-phenylamino-2-azaspiro[4.4]nonane- and [4.5]decane-1,3-dione derivatives has been determined by reversed-phase thin-layer chromatography with n-propanol-Tris buffer (pH 7.4) mixtures as mobile phases. Examination of chromatographic behaviour revealed a linear correlation between R(M) values and the concentration of n-propanol in the mobile phase. The partition coefficients (logP) were also calculated by use of the PrologP module of the Pallas computer program. Comparison of R(M0) values and calculated (logP(PALLAS)) data revealed the correlation expressed by the equation: logP(PALLAS) = 0.9995 R(M0) + 1.3451 (n = 28; r = 0.8971; F = 107.13; p < 0.05). The role of the lipophilicity in the anticonvulsant activity of a set of compounds examined is discussed: the active anticonvulsants were less lipophilic than inactive ones.     

Improvement of cubic silicon carbide crystals grown from solution

Cubic-silicon carbide crystals have been grown from carbon-rich silicon solutions using the travelling-zone method. To improve the growth process, we investigated the effect of controlling more tightly some of the growth parameters. Using such improved growth conditions, our best sample is a 12 mm diameter and 3 mm long 3C–SiC crystal. It is grown on a (0001) 2 off, 6H–SiC seed and has 111-orientation. The low amount of silicon inclusions results in a reduced internal stress, which is demonstrated by the consideration of μ-Raman spectra collected at room temperature on a large number of samples.     

Identification of ionic liquid components by RP‐HPLC with diode array detector using chaotropic effect and perturbation technique

Sodium hexafluorophosphate, perchlorate and tetrafluoroborate were applied as the ion‐pair reagents in reversed‐phase chromatography of several imidazolium‐based ionic liquids. The optimization of the retention was performed by changing the kind of organic modifier (methanol, acetonitrile), concentration and the kind of the ion‐pair reagents in the mobile phase and the column kind (Zorbax SB‐C18, Zorbax SB‐Phenyl, Zorbax SB‐CN, Zorbax SB‐NH₂ and Supelcosil LC‐F). The selectivity of the proposed chromatographic systems according to the cation kind was compared on the basis of the resolution of ionic liquid mixture. The perturbation method was applied to identify the anion kind. The formation of ion‐associated complexes between promethazine as counter‐cation and chaotropic anions controlling their retention was confirmed.     

On similarity of hydrogen-bonded networks in liquid formamide and water as revealed in the static dielectric studies

The paper presents the experimental verification of the result obtained with the molecular dynamics simulation which revealed the differences in the topology of the hydrogen-bonded networks in liquid formamide and water, namely, the differences in their intermolecular cyclization process (I. Bakó, et al. J. Chem. Phys. 2010, 132, 014506). It is shown in our paper that the difference in the (simulated) size distribution of the hydrogen-bonded molecular rings in water (a relatively sharp maximum at about 6 molecules) and formamide (a broad maximum at about 11 molecules) strongly manifests itself in the experimental values of the Kirkwood correlation factor of the compounds. A much larger number of molecules included in the cyclic species (of more or less compensated dipole moment) leads to significant decrease of the Kirkwood correlation factor of formamide in comparison to that of water. Besides, as a consequence of an enhancement in formation of the cyclic multimers of formamide, one observes an essential reduction of the orientational entropy increment of that liquid, in comparison to the entropy effect related to liquid amides where the chain multimers are formed.     

The chemical composition of the essential oils of Cirsium palustre and C. rivulare and their antiproliferative effect

The composition of the essential oils of Cirsium palustre and C. rivulare and their antiproliferative activity against breast adenocarcinoma cells (MCF-7 and MDA-MBA-231) were investigated. The essential oils obtained by hydro-distillation from the roots (yield 0.2 and 0.1% v/w, respectively), leaves and inflorescences (yield below 0.01%), were analyzed by gas chromatography coupled with mass spectrometry (GC-MS). The composition of the essential oils in the respective organs of each plant differed considerably. On the other hand, similarities were observed in the composition of root and leaf oils. In C. palustre and C. rivulare root oil, 50 and 39 constituents were identified, accounting for 95.3% and 92.4% of the total content. The main components were aplotaxene and its derivatives, representing 78.6% and 46.6% of the total content. In leaf oils of both species, 59 and 49 compounds, respectively, were identified, representing 67.4% and 78.3% of the total content. The major constituents were beta-damascenone (4.1% and 13.4%, respectively) and beta-ionone (6.7% and 5.3%, respectively). Short-chain saturated and unsaturated aliphatic alcohols and aldehydes constituted another important group of compounds (17.7% and 9.0%, respectively). The essential oils of the roots have moderate anti-proliferative activity, with IC50 values ranging from 110 to 140 microg/mL. These concentrations were below the level able to inhibit the proliferation of healthy cells.     

Modelling relation between oxidation resistance and tribological properties of non-toxic lubricants with the use of artificial neural networks

The lubricants based on vegetable oils, as environmental friendly, are urgently sought. However, in addition to ecological characteristics, the lubricating properties have to be met. To meet these requirements the active additives influencing the lubricating properties and oxidation resistance are used. The useful lifetime of lubricants is determined largely by their abilities to resist oxidation. The article presented the results of new, ecological lubricants development. The oxidation performances of different developed lubricants have been tested. The experimentally determined oxidation stability of the compositions based on vegetable oils are presented. Analysed oxidation onset temperature was obtained from the differential scanning calorimetry (DSC) curves, which provides the rapid prediction of the oxidative stability of lubricants. Besides the lubricating composition based on vegetable oils, the developed greases-based mineral, or synthetic oil were investigated. The properties of these greases were evaluated using the measurement of parameters describing structure (penetration) and resistance to high temperature (dropping point). The lubricating properties of both the greases and vegetable oil compositions were tested on four-ball testing machine. In the results of the modelling of the lubricating properties the neural network models for the both types of the lubricants were developed. A discussion of the research results and analysis of models validity is given below. The experimental results are compared with the calculated using the neural models. An acceptable agreement was achieved.     

Thermal degradation of copolymers based on selected alkyl methacrylates

The thermal stability and thermal degradation of copolymers based on selected alkyl methacrylates at temperatures between 250 and 400?°C have been studied using pyrolysis?Cgas chromatography. The type and composition of thermal degradation products gave useful information about the mechanism of pyrolysis of copolymers synthesized by using typical commercially available alkyl methacrylates. It was observed that the main thermal degradation products from alkyl methacrylate copolymers are monomers of alkyl methacrylates using by synthesis. Other pyrolysis by-products formed during thermal degradation were carbon dioxide, carbon monoxide, methane, ethane, methanol, ethanol, and propanol-1.     

Conciliating the nonadditive entropy approach and the fractional model formulation when describing subdiffusion

We consider here two different models describing subdiffusion. One of them is derived from Continuous Time Random Walk formalism and utilizes a subdiffusion equation with a fractional time derivative. The second model is based on Sharma-Mittal nonadditive entropy formalism where the subdiffusive process is described by a nonlinear equation with ordinary derivatives. Using these two models we describe the process of a substance released from a thick membrane and we find functions which determine the time evolution of the amount of substance remaining inside this membrane. We then find ‘the agreement conditions’ under which these two models provide the same relation defining subdiffusion and give the same function characterizing the process of the released substance. These agreement conditions enable us to determine the relation between the parameters occuring in both models.     

Azothia- and Azoxythiacrown Ethers as Ion Carriers. Part I. Cationic Response of Membrane Electrodes

13-Membered azothia- and azoxythiacrown ethers have been applied as ion carriers in ion-selective membrane electrodes. Their sensitivity and selectivity were studied towards alkali, alkaline earth, transition and heavy metal cations. It was found that membranes doped with the azoxythiacrown ether (A) show higher affinity towards Pb²⁺ than Cu²⁺ (log K_Cu,Pb ^pot = 1.7), whereas membranes with the azothiacrown ether (B) are more selective towards Cu²⁺ than Pb²⁺ (log K_Cu,Pb ^pot = -2.4). The discrimination of alkali and alkaline earth cations was found to be greater for B than for A. Electrodes with both ionophores suffered from strong interference by Ag⁺ and Hg²⁺. The relation between the carrier structure and electrode properties has been discussed.