The role of F-N reagent and reaction conditions on fluoro functionalisation of substituted phenols

The effect of steric interactions on the regioselectivity of fluorination of para alkyl substituted phenols was investigated and the strong effect of size of the alkyl substituent, the structure of the F-N reagent and the solvent on the site of fluorination was established. The course of reaction obeyed a second order rate equation, while the fluorination process required higher ΔH^≠ activation than oxidation or oxidative demethylation. Solvent polarity variations had a small effect on the rate of functionalisation, while an excellent Hammett correlation with ρ⁺=−2.3 was determined.     

Performance evaluation of CAESAR–QSAR output using PAHs as a case study

The set of 16 polycyclic aromatic hydrocarbon compounds was examined with the Internet available quantitative structure–activity relationship (QSAR) CAESAR models. For mutagenicity, carcinogenicity, developmental toxicity, and skin sensitization, the report includes the predicted classifications, the analysis of applicability domains, and the similarity sets, which consist of the similar compounds from the training sets. These results were further analyzed with chemometrical methods, that is, hierarchical clustering, principal component analysis, and self‐organizing maps, which were used for clustering and to define the cluster indicators. Such analysis assists the users in planning the application of QSAR models for hazard communication in regulatory compliance and in research of new active compounds. Copyright © 2013 John Wiley & Sons, Ltd.     

Characterization of carboxylic acids in atmospheric aerosols using hydrophilic interaction liquid chromatography tandem mass spectrometry

A sensitive hydrophilic interaction liquid chromatography/electrospray ionization mass spectrometry (HILIC/ESI-MS/MS) method was developed for determination of selected aliphatic (i.e. malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic, maleic, fumaric, glycolic and pyruvic acid), alicyclic (i.e. cis-pinonic and pinic acid) and aromatic (i.e. trimesic, phthalic acid and its isomers) carboxylic acids. Analytes were separated on an amide column using a gradient elution with a 10mM constant ionic strength mobile phase containing acetonitrile and aqueous ammonium acetate buffer (pH 5.0). The influence of the buffer type, pH, polar modifier and temperature on analyte retention under HILIC was studied. Static sonication-assisted solvent extraction was optimized for sample preparation prior to analysis. The recoveries obtained were higher than 90% for most analytes. The method was proven to be sensitive with limits of detection ranged from 0.03 to 16.0 μg/L in selected reaction monitoring mode (SRM). The repeatability and intermediate precision of the method, expressed as RSD (%) of the peak area ratio between analytes and their internal standards were generally lower than 5%. The method was successfully applied for determination of the studied acids in samples of ambient aerosol particles. A big advantage of the new method is also its ability to detect and separate the isobaric compounds of the selected carboxylic acids. Our results demonstrate that the method is specific and sensitive for the determination of a wider range of polar carboxylic acids at low concentrations in complex samples of aerosol particles.     

Meldrum's acid catalyzed reaction of tetracyanoethylene and aldehydes in water: a novel approach to arylidenemalononitrile

Meldrum's acid catalyzed the reaction of tetracyanoethylene with aromatic, heteroaromatic, and conjugated aldehydes led to arylidenemalononitrile in water in good yields at 80 degrees C. The work-up of reactions is very simple and the crude products are sufficiently pure to be used without further purification. The procedure provides an alternative method for the synthesis of arylidenemalononitrile.     

Synthetic Approaches towards the Sulfonamide Substituted‐1,5‐Diarylimidazole‐2‐thiones as Selective Cyclooxygense‐2 inhibitors

A new series of sulfonamide substituted 1,5‐diarylimidazole, possessing C‐2 alkylthio moiety, were synthesized for their cyclooxygense‐2 (COX‐2) inhibitory activity starting from condensation of N,N‐dibenzylaminosulfonylphenacylamine hydrochloride ( 2 ) and corresponding isothiocyanate in the presence of Et₃N, followed by alkylation in the basic medium. In concomitant with these intermediates, 2‐arylamino‐5‐arylthiazole derivatives 5 were also produced. The ratio of these two products was variable with different isothiocyanates. Final debenzylation was achieved using concentrated sulfuric acid to give the title sulfonamides 8 .     

Electrophoretic deposition as a tool for separation of protein inclusion bodies from host bacteria in suspension

This paper shows, for the first time, that the electrophoretic deposition technique is able to selectively collect protein inclusion bodies (PBs) from the host bacteria suspensions. In the first step, zeta potential as a function of pH is carefully determined for both species involved. Based on the obtained dependencies, the pH of the mixture of PBs and bacteria is precisely adjusted and the electrophoretic experiment is carried out. We show that the efficiency of separation and the yield depends not only on the electrokinetic properties of given species but also on the electrode composition and surface morphology. The deposited species are easily removed by forced washing or reverse electric field. As a whole, the selectivity and the yields are higher than in most alternative state-of-the art techniques.     

The Origin of the Selectivity and Activity of Ruthenium‐Cluster Catalysts for Fuel‐Cell Feed‐Gas Purification: A Gas‐Phase Approach

Gas‐phase ruthenium clusters Ru_n⁺ (n=2–6) are employed as model systems to discover the origin of the outstanding performance of supported sub‐nanometer ruthenium particles in the catalytic CO methanation reaction with relevance to the hydrogen feed‐gas purification for advanced fuel‐cell applications. Using ion‐trap mass spectrometry in conjunction with first‐principles density functional theory calculations three fundamental properties of these clusters are identified which determine the selectivity and catalytic activity: high reactivity toward CO in contrast to inertness in the reaction with CO₂; promotion of cooperatively enhanced H₂ coadsorption and dissociation on pre‐formed ruthenium carbonyl clusters, that is, no CO poisoning occurs; and the presence of Ru‐atom sites with a low number of metal–metal bonds, which are particularly active for H₂ coadsorption and activation. Furthermore, comprehensive theoretical investigations provide mechanistic insight into the CO methanation reaction and discover a reaction route involving the formation of a formyl‐type intermediate.     

Facile synthesis of highly substituted 2-pyrone derivatives via a tandem Knoevenagel condensation/lactonization reaction of β-formyl-esters and 1,3-cyclohexadiones

A mild and efficient tandem process for the synthesis of new highly substituted 2-pyrones starting from commercially available 2-arylacetic acids has been developed. The synthesis is based on the Knoevenagel condensation of 1,3-cyclohexadiones with various β-formyl-esters, followed by lactonization in the presence of nano ZnO (20 mol %). Moderate to high yields and readily available cheap starting materials are the key features of the present method.     

Investigation of the solubilization of car-emitted Pt,Pd and Rh in street dust and spiked soil samples

A sequential extraction procedure (three-step), proposed by the Standards, Measurements and Testing Programme (formerly BCR) of the European Union, was applied to street dust and spiked soil samples for the determination of PGEs. Analyses were carried out using inductively coupled plasma-mass spectrometry (ICP-MS). The results indicate that up to 5% from Pt, 70% from Pd and 14% from Rh are in mobile forms in street dust. The results for the soil samples spiked with crushed catalytic converter are significantly lower indicating that PGEs are oxidised more efficiently in natural conditions. Additionally Pt and Pd bound to humic acids were investigated.