Structural identification of fatty acid methyl esters by collision spectra of their [M ? H]− species

Negative ion chemical ionization linked to collisionally activated decomposition (CAD) experiments has proved to be an efficient analytical tool in mass spectrometric characterization of fatty acids. The CAD mass-analysed ion kinetic energy spectra of [M ? H]^? species, obtained by OH^? reaction with a selection of six C₁₈ fatty acid methyl esters, reveal useful correlations with the original structure of the neutrals, giving evidence of both chain branching and double bond positions.     

Effects of temperature on the concentration of polycyclic aromatic hydrocarbons (PAHs) adsorbed onto airborne particulates

Summary Daily samples of airborne particulates (143) were collected along the year in La Spezia (Italy). Seasonal variations of atmospheric PAH concentrations, with highest winter values, have been observed. The concentration of PAHs was found to correlate negatively with the mean ambient temperature during the sampling period. Volatilization, photodegradation and seasonal modifications of emissions from urban traffic were found to be a possible explanation of this phenomenon.     

Morphological and structural characterization of polypropylene/conductive graphite nanocomposites

The structure and morphology of polypropylene/conductive graphite (PP/CG) composites were studied by wide angle X-ray diffraction, small-angle X-ray scattering and scanning electron microscopy. An effect of graphite on the crystallization behavior was observed and the opposite influences of enhanced thermal conductivity and hinder of chain mobility on the formation of the γ-phase of PP were discussed.     

Variable-temperature X-ray crystallographic and DFT computational study of the N-H...O/N...H-O tautomeric competition in 1-(Arylazo)-2-naphthols. Outline of a transition-state hydrogen-bond theory

Phenyl-substituted 1-arylazo-2-naphthols (AAN) display ...HN-N=C-C=O... <==>...N=N-C=C-OH... ketohydrazone-azoenol tautomerism and can form intramolecular resonance-assisted H-bonds from pure N-H...O to pure N...H-O through tautomeric and dynamically disordered N-H...O <==>N...H-O bonds according to the electronic properties of their substituents. Three compounds of this series (m-OCH(3)-AAN = mOM; p-Cl-AAN = pCl; and p-NMe(2)-AAN = pNM2) have been studied by X-ray crystallography at four temperatures (100-295 K), showing that the remarkably short H-bonds formed (2.53 < or = d(N...O) < or = 2.55 A) are a pure N-H...O in mOM, a dynamically disordered mixture in pCl (N-H...O:N...H-O = 69:31 at 100 K), and a statically disordered mixture in pNM2 (N-H...O:N...H-O = 21:79 at 100 K). These compounds, integrated by the p-H-, p-NO(2)-, p-F-, and p-O(-)-substituted derivatives, have been emulated by DFT methods (B3LYP/6-31+G(d,p) level) with full geometry optimization of the stationary points along the proton-transfer (PT) pathway: N-H...O and N...H-O ground states and N...H...O transition state. Analysis of DFT-calculated energies and geometries by the methods of the rate-equilibrium Marcus theory shows that all H-bond features (stability and tautomerism, as well as position and height of the PT barrier) can be coherently interpreted in the frame of the transition-state (or activated-complex) theory by considering the bond as a chemical reaction N-H...O <==> N...H...O <==> N...H-O which is bimolecular in both directions and proceeds via the N...H...O PT transition state (the activated complex).     

Selective voltammetric detection of dopamine in the presence of ascorbate

The selective detection of dopamine in the presence of ascorbate is demonstrated based on the voltammetry of dopamine transfer across the interface between two immiscible electrolyte solutions (ITIES) facilitated by an organic-phase ionophore; ascorbate transfer does not occur, leading to highly selective detection of dopamine in the presence of excess ascorbate.     

Decomposition of Nitrous Oxide on CoOX/ZrO2, CuOX/ZrO2 and FeOX/ZrO2 Catalysts

On CoO_x/ZrO₂, CuO_x/ZrO₂ and FeO_x/ZrO₂ catalysts, below the limits shown by characterization to have high metal dispersion, the turnover frequency for N₂O decomposition is nearly independent of metal content.     

New C(2)‐substituted 8‐alkylsulfanyl‐9‐phenylmethyl‐hypoxanthines III

Title compounds were obtained starting from the key imidazole intermediate, 5‐amino‐1‐phenyl‐methyl‐2‐mercapto‐1H‐imidazole‐4‐carboxylic acid amide 5 , readily derived from the base catalyzed rearrangement of a thiazole, 5‐amino‐2‐phenylmethylaminothiazole‐4‐carboxylic acid amide 4 . Alkylation of the thiol function on 5 with phenylmethyl and allylic chlorides gave compounds 6 and 7 respectively. Cyclization of 6 with a variety of esters afforded 8‐phenylmethylthiohypoxanthines, 8–11 . Similarly, 7 was cyclized to 8‐allylthiohypoxanthines, 20–21 . Compound 5 was also cyclized, but formed 8‐mercaptohypox‐anthines, 22–24 . Alkylation of 8‐mercaptohypoxanthines afforded 8‐alkylthiohypoxanthines, 8, 9,25 and 26 (see Scheme 2). Chlorination of 9–11 afforded 16–18 ; adenine 19 was derived from 16 . Oxidation of hypox‐anthines 8–11 with m‐chloroperbenzoic acid gave the corresponding 8‐phenylmethylsulfonyl derivatives 12 ‐ 15 . These derivatives proved resistant to nucleophilic displacement reactions with primary amines.     

Multicomponent Hantzsch cyclocondensation as a route to highly functionalized 2- and 4-dihydropyridylalanines, 2- and 4-pyridylalanines, and their N-oxides: preparation via a polymer-assisted solution-phase approach

An improved and efficient entry to highly functionalized β-(2-pyridyl)- and β-(4-pyridyl)alanines and the corresponding 1,4-dihydro and N-oxide derivatives has been developed by one-pot thermal Hantzsch-type cyclocondensation of aldehyde-ketoester-enamine systems in which one of the reagents (aldehyde or ketoester) was carrying the unmasked but protected chiral glycinyl moiety. Thus coupling N-Boc-O-benzyl aspartate β-aldehyde, acetoacetate and aminocrotonate esters afforded tetrasubstituted β-(4-dihydropyridyl)alanines (75% yield). One of these products was almost quantitatively transformed into the β-(4-pyridyl)alanine derivative which in turn was oxidized to the corresponding N-oxide. Each of these enantiomerically pure (Mosher's amide analysis) heterocyclic α-amino acids was incorporated into a tripeptide by coupling with (S)-phenylalanine. In a similar way tetrasubstituted β-(2-dihydropyridyl)alanine, β-(2-pyridyl)alanine and β-(1-oxido-2-pyridyl)alanine were prepared via Hantzsch cyclocondensation reaction using benzaldehyde, aminocrotonate, and acetoacetate carrying the N-Boc-O-benzyl glycinate moiety. It was shown that the work up of the reaction mixtures derived from the cyclocondensation and oxidation reactions can be carried out by the use of polymer supported reagents and sequestrants thus allowing the isolation of the products in high purity without any chromatography.     

New 1,2,3‐triazolo[4,5‐d]1,2,4‐triazolo[3,4‐b]pyridazine derivatives II

New tricyclic 1,2,3‐triazolo‐1,2,4‐triazolo‐pyridazine derivatives, bearing a methyl substituent on the 1,2,3‐triazole ring, were prepared as potential biological agents. N‐Methylation of dimethyl 1,2,3‐triazole‐4,5‐dicarboxylate allowed synthesis of the isomeric 1‐methyl‐4,7‐dihydroxy and 2‐methyl‐4,7‐dihydroxy triazolo‐pyridazines 4a and 4b which, by a chlorination reaction, gave the corresponding 1‐methyl‐4‐chloro‐( 6a ), 1‐methyl‐7‐chloro‐ ( 6b ) and 2‐methyl‐4‐chloro‐ ( 9 ) substituted 1,2,3‐triazolo‐pyridazines. The nucle‐ophilic substitution with hydrazine hydrate and the suitable cyclization to form the 1,2,4‐triazole ring, provided the expected tricyclic isomeric derivatives 8a, 8b and 11 respectively. The p‐methoxybenzyl substituent, introduced as a leaving group to obtain either v‐triazolo‐pyridazine or v‐triazolo‐s‐triazolo‐pyri‐dazine derivatives unsubstituted on the 1,2,3‐triazole ring, appeared inadequate. Some compounds underwent binding assays toward the adenosine A₁and A_2A receptors.     

Large‐area,polarisation‐sensitive plasmonic materials from colloidal lithography

The development of simple to prepare, polarization‐sensitive plasmonic apertures with two plasmonic modes, is described. To achieve these results, monocrystalline nanosphere lithography masks of 438 nm polystyrene spheres are modified with reactive ion etching before silver is subsequently evaporated through the mask at varied angles. As the angle of evaporation increases, round apertures, elliptical apertures or lines with bow‐tie like features between two lines are produced. A primary plasmon mode is shown at 570 nm, while a tunable plasmon mode is demonstrated between 700 nm and 900 nm. Finite‐difference time‐domain calculations agree with the observed results and predict that this method of fabrication can produce tunable plasmonic features throughout the NIR optical telecommunication wavelength range. Lastly, the excitation polarization angle is compared with that of plasmonic nanorods and asymmetric nano‐apertures systems to describe why the excitation polarization of the low energy mode is orthogonal to the long axis of the apertures. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)