Step by step palladium mediated syntheses of new 2-(pyridin-2-yl)-6-R-nicotinic acids and esters

Taking advantage of palladium peculiar “rollover” C,N cyclometallation, it is possible to promote C(3) functionalization of 6-alkyl-substituted-2,2′-bipyridines. The carbonylation reaction of rollover species [Pd(Lⁿ)Cl]₂, (HL¹ = 6-isopropyl-2,2′-bipy, 1; HL² = 6-neopentyl-2,2′-bipy, 2; HL³ = 6-ethyl-2,2′-bipy, 3; HL⁴ = 6-methyl-2,2′-bipy, 4) allowed the synthesis of 2-(pyridin-2-yl)-6-alkyl-nicotinic acids or esters. These nicotinic derivatives are extremely rare and, as far as we know, quite unreported in the case of the 6-substituted molecules.     

Magnetic properties of the Fe spin crossover complex in emulsion polymerization of trifluoroethylmethacrylate using poly(vinyl alcohol)

Influence of chemical substitution in the Fe^II spin crossover complex on magnetic properties in emulsion polymerization of trifluoroethylmethacrylate using poly(vinyl alcohol) as a protective colloid was investigated near its high spin/low spin (HS/LS) phase transition. The obvious bi-stability of the HS/LS phase transition was considered by the identification of multiple spin states between the quintet (S=2) states to single state (S=0) across the excited triplet state (S=1). Magnetic parameters of gradual shifts of anisotropy g-tensor supported by the molecular distortion of the spin crossover complex would arise from a Jahn-Teller effect regarding ligand field theory on the basis of a B3LYP density functional theory using electron spin resonance (ESR) spectrum and X-ray powder diffraction.     

Multivariate statistical analysis of tobacco of different origin, grade and variety according to polyphenols and organic acids

The aim of this work was to determine the concentration of polyphenols, organic acids in tobacco of different areas, grades and varieties by ultra-performance liquid chromatography tandem mass spectrometry (UPLC/MS/MS) and to achieve statistical classification by principal component analysis (PCA) and linear discriminant analysis (LDA). The obtained results revealed that tobacco of different varieties can be correctly classified according to the contents of polyphenols or organic acid. The results of PCA showed that different grades and geographic regions cannot completely be discriminated using polyphenols or organic acid as independent variables. However, there were marked differences in special class from the same type or grade tobacco. At the same time, the results of LDA also showed that the samples were correctly classified at 100% for different varieties of tobacco, but only 55.3% and 60% for different grades and areas, respectively. These results demonstrated that the composition of polyphenols and organic acids can be used as the useful variables to characterize the type and the special class or grade of tobacco.     

Study and characterization of mural paintings from XIX Century in a noble Venetian (Italy) palace

The present paper describes the characterization carried out on the roof of a private palace located in the historical center of Venice (Italy). We focused our attention on the studies of original constituent materials (pigments and binders), in order to identify the pictorial technique of the artist and verify the stylistic attribution to Giuseppe Borsato, a Venetian painter operating between 18th and 19th century. Characterization of collected samples was carried on using both conventional and advanced analytical techniques, such as Optical Microscopy and Scanning Electron Microscopy coupled with Energy Dispersive X-Ray (SEM–EDS) microscopy, Fourier Transform Infrared Spectroscopy (FTIR) and High Performance Liquid Chromatography (HPLC) coupled with photodiode array detection (DAD) and Mass Spectrometry (MS). The finding of dating pigments (such as Cobalt blue and Cu–As based green) and of a complex binding's mixture compatible with the considered supposed period, allowed us to confirm the attribution hypothesis.     

Quantification of organic acids in beer by nuclear magnetic resonance (NMR)-based methods

The organic acids present in beer provide important information on the product's quality and history, determining organoleptic properties and being useful indicators of fermentation performance. NMR spectroscopy may be used for rapid quantification of organic acids in beer and different NMR-based methodologies are hereby compared for the six main acids found in beer (acetic, citric, lactic, malic, pyruvic and succinic). The use of partial least squares (PLS) regression enables faster quantification, compared to traditional integration methods, and the performance of PLS models built using different reference methods (capillary electrophoresis (CE), both with direct and indirect UV detection, and enzymatic essays) was investigated. The best multivariate models were obtained using CE/indirect detection and enzymatic essays as reference and their response was compared with NMR integration, either using an internal reference or an electrical reference signal (Electronic REference To access In vivo Concentrations, ERETIC). NMR integration results generally agree with those obtained by PLS, with some overestimation for malic and pyruvic acids, probably due to peak overlap and subsequent integral errors, and an apparent relative underestimation for citric acid. Overall, these results make the PLS-NMR method an interesting choice for organic acid quantification in beer.     

Mechanical and thermal properties and flame retardancy of phosphorus-containing polyhedral oligomeric silsesquioxane (DOPO-POSS)/polycarbonate composites

A novel polyhedral oligomeric silsesquioxane containing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-POSS) has been incorporated into polycarbonate (PC) composites in order to study its effect on mechanical and thermal properties and flame retardancy. The mechanical and thermal properties of the DOPO-POSS/PC composites have been investigated by tensile and flexural testing, DSC, and DMA. Slight enhancements of yield stress, and flexural strength and modulus, and obvious decreases of fracture strength and strain of the DOPO-POSS/PC composites were observed with an increase in DOPO-POSS loading. The glass transition temperatures (T_g) of the composites were reduced with increasing DOPO-POSS loading. The morphology of the PC composites was evaluated by SEM, which indicated that the DOPO-POSS was dispersed with a particle size of 100-250 nm in the PC matrix. The thermal degradation behaviour and flame retardancies of PC composites with different DOPO-POSS loadings were investigated by TGA, LOI, UL-94 standard, and cone calorimetry. The composite had an LOI value of 30.5 and a UL-94 rating V-0 when the content of DOPO-POSS was 4%.     

Comprehensive two-dimensional liquid chromatography: Ion chromatography × reversed-phase liquid chromatography for separation of low-molar-mass organic acids

In the work presented here a novel approach to comprehensive two-dimensional liquid chromatography is evaluated. Ion chromatography is chosen for the first-dimension separation and reversed-phase liquid chromatography is chosen for the second-dimension separation mode. The coupling of these modes is made possible by neutralising the first-dimension effluent, containing KOH, prior to transfer to the second-dimension reversed-phase column. A test mixture of 24 low-molar-mass organic acids is used for optimisation of the system. Three food and beverage samples were analysed in order to evaluate the developed methodology, the resulting two-dimensional separation is near-orthogonal, the set-up is simple and all instrumental components are available commercially. The method proved to be robust and suitable for the analysis of wine, orange juice and yogurt.     

Aliphatic carboxylic acids and alcohols as efficiency and elution strength enhancers in micellar liquid chromatography

Micellar liquid chromatography (MLC) uses surfactant solutions as mobile phases with added organic additives to enhance both the elution strength and the chromatographic efficiency. Two aliphatic carboxylic acids (1-butanoic and 1-pentanoic) were used as MLC additives and compared with the two corresponding alcohols (1-butanol, 1-pentanol) in terms of elution strength, efficiency and selectivity. A set of 11 phenol derivatives was used as probe compounds. All micellar mobile phases were prepared with sodium dodecylsulfate (SDS) with concentration ranging from 0.05 to 0.15 M and the modifier content within 1.0 and 5.0% (v/v). The elution strength of different mobile phases containing a constant amount of SDS and different amounts of modifiers; and mobile phases containing a constant amount of modifier and different SDS concentration were determined and discussed. The effect of the acid modifiers on efficiency was studied constructing van Deemter plots that showed no minimum within the 0.01–0.7 mL/min flow rate range studied. Temperature effects were also studied constructing the classical van’t Hoff plots. The slight curvature of the plots in the 25–70 °C range may indicate some modification of the surfactant-bonded moiety layer on the stationary phase surface. Since no definitive advantage of the use of aliphatic acids were established compared to their alcohol counterpart, their terrible smell will probably preclude their use as MLC organic modifiers.     

Active-sodium-promoted reductive cleavage of halogenated benzoic acids

The outcome of the reaction between 1,2-diaryl-1,2-disodioethanes and halogenated benzoic acids strongly depends on the nature of both reaction partners. Indeed, whilst chloro-, bromo- and iodobenzoic acids are easily dehalogenated, the reductive cleavage of fluorobenzoic acids proceeds to a high extent only in the presence of the dianions endowed with more powerful reducing properties. Moreover, it was observed that ortho-substituted benzoic acids are more easily dehalogenated than the corresponding para or meta isomers. These observations allowed the development of reaction conditions for the exhaustive or regioselective cleavage of selected polyhalogenated benzoic acids.     

Synthesis of soluble oligothiophenes bearing cyano groups, their optical and electrochemical properties

The synthesis and the characterization of twelve new soluble oligothiophenes, possessing two to four 3,4-dicyanothiophene units in their backbone, are described. These semiconductors are prepared through Stille coupling and/or homo-coupling reactions. Cyclic voltammetry studies have been performed to evaluate their stability as n-type semiconducting materials under ambient conditions. The measured electrochemical and optical properties are fully supported by quantum-chemical calculations.