Dinuclear Lanthanide (III) coordination polymers in a domino reaction

A systematic study was performed to further optimise the catalytic room-temperature synthesis of trans-4,5- diaminocyclopent-2-enones from 2-furaldehyde and primary or secondary amines under a non-inert atmosphere. For this purpose, a series of dinuclear lanthanide (III) coordination polymers were synthesised using a dianionic Schiff base and their catalytic activities were investigated

Highly selective hydrogenation of furfural over supported Pt nanoparticles under mild conditions

The selective liquid phase hydrogenation of furfural to furfuryl alcohol over Pt nanoparticles supported on SiO₂, ZnO, γ-Al2O₃, CeO₂ is reported under extremely mild conditions. Ambient hydrogen pressure, and temperatures as low as 50 °C are shown sufficient to drive furfural hydrogenation with high conversion and >99% selectivity to furfuryl alcohol. Strong support and solvent dependencies are observed, with methanol and n-butanol proving excellent solvents for promoting high furfuryl alcohol yields over uniformly dispersed 4 nm Pt nanoparticles over MgO, CeO₂ and γ-Al₂O₃. In contrast, non-polar solvents conferred poor furfural conversion, while ethanol favored acetal by-product formation. Furfural selective hydrogenation can be tuned through controlling the oxide support, reaction solvent and temperature

Stir Bar Sorptive Extraction of Volatile Compounds in Vinegar: Validation Study and Comparison With Solid Phase Microextraction

Stir bar sorptive extraction was evaluated for analysing volatiles in vinegar. The procedure developed shows detection and quantitation limits, and linear ranges adequate for analysing this type of compounds. The accuracy obtained was close to 100%, with repeatability values lower than 13%. The extraction efficiency is inversely affected by the acetic acid content. Although the absolute areas decrease, the compound area/internal standard area ratio remains constant, so for quantitative analysis, the acetic acid concentration does not affect the analytical data. The method was compared with a previous SPME method. Similar performance characteristics were obtained for both methodologies, with lower detection and quantitation limits and better repeatability reproducibility values for SBSE. Both analytical methods were used to analyse a variety of vinegars. The results obtained from both methods were in agreemen

Headspace Solid-Phase Microextraction Coupled with Gas Chromatography-Mass Spectrometric Analysis of Volatile Components of Raw and Stir-Fried Fruit of C. Pinnatifida (FCP)

Purpose: To investigate the change of volatile components associated with odor of C. Pinnatifida (FCP) fruit and its stir-fried forms.Methods: FCP fruit was stir-fried and monitored by an online-type and non-contact temperature measurement system (ONTMS). Headspace solid-phase  microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was used to analyze the volatile composition of raw FCP and its various stir-fried forms.Results: The color of FCP turned darker with the stir-frying process. In all, 47 volatile compounds with contents > 1 % were identified. The major volatile components were methyl acetate (4.40 %), n-hexane (2.90 %), 2-methyl-furan (1.80 %), 3-methyl-butyraldehyde (3.64 %), hexanal (2.08 %), furaldehyde (5.77 %), and D-limonene (7.99 %) in raw FCP. Following stir-frying, the contents of furaldehyde, 5- methyl-furaldehyde, methyl acetate, 2-methyl-butyraldehyde, D-limonene and 2-methyl-furaldehyde were altered significantly, which might have resulted in odor changes.Conclusion: HS-SPME coupled with GC-MS is a rapid and eco-friendly method with the potential to analyze volatile compounds in raw and processed FCP.Keywords: Crataegus pinnatifida, Stir-frying, Online-type and non-contact temperature measurement system, Headspace solid-phase microextraction, Volatile components, Odo

High performance liquid chromatographic determination of 2-furaldehyde and 5-hydroxymethyl-2-furaldehyde in honey

A method of determination of 2-furaldehyde (F) and 5-hydroxymethyl-2-furaldehyde (HMF) in honey by high-performance liquid chromatography (HPLC) is described. The method is based on the formation of the 2,4-dinitrophenylhydrazones of carbonyl compounds and subsequent reversed-phase separation of these derivatives. Derivatization is carried out by utilizing an acidic solution of 2,4-dinitrophenylhydrazine in acetonitrile. Precipitation of the derivatives of carbonyl compounds is thus avoided and direct injection of the sample into the HPLC system is allowed. The procedure offers a high specificity, since the derivatives of F and HMF are well separated from the other components of the mixture under examination. Recoveries of 95-99% were obtained from honey spiked at different levels with both analytes. The detection limit is of the order of 10 \u3bcg/kg of honey and reproducibility (mean of six determinations) is \ub13% for F and \ub12% for HMF

The odour of white bread

Volatile constituents of white bread were investigated. Different methods were used for isolating and concentrating components to avoid artefacts as far as possible. Especially good was enlarged vapour analysis. Ninety-four components were identified, including hydrocarbons, alcohols, aldehydes, ketones, acids, esters as well as nitrogen, sulphur and miscellaneous compounds. The concentration of the main components in the vapour above white bread was determined by direct vapour analysis. The odour threshold values of these components in aqueous solution were determined, and the odour values calculated as the ratio of concentration to odour threshold value to estimate their contribution to the total odour. The Maillard reaction of the cysteine/cystine-ribose system was investigated in a search for components which can be expected in heat-processed food products, and to find out whether during this reaction compounds possessing bread-like odours were formed. Forty-five components were identified, including thiophenes, thiazoles, thiols, pyrazines, pyrroles, amines, furans, aldehydes, ketones and miscellaneous compounds. Possible pathways for the formation of 2-acylthiazoles and of 3-methyl, and 5-methyl substituted 2-formylthiophenes are proposed

Synthesis and Antibacterial Studies of Some 2-Furanthiocarboxyhydrazones

Seven 2-furanthiocarboxyhydrazones were prepared, 5-nitro-furaldehyde-2-furanthiocarboxyhydrazone from the reaction of 2-furanthiocarboxyhydrazide with 5-nitro-2-furaldiacetate and the others from the condensation of 2-furanthiocarboxyhydrazide with aldehydes: 2- furaldehyde, benzaldehyde, p-hydroxybenzaldehyde, o-methoxybenzaldehyde, o-vanillin, and salicylaldehyde. The seven 2-furanthiocarboxyhydrazones were tested for their antibacterial activities against Staphyloccocus aureus and Bacillus subtilis. 5-Nitro-2-furaldehyde-2- furanthiocarboxyhydrazone was found to display the strongest bacterotoxicity

Geochemical analysis of Cenozoic fossil conifers at high latitudes: Implications for molecular preservation and environmental change

Fossil materials record ancient life and their adapted environment. Arctic plant fossils are critical for our understanding of the Earth’s paleoenvironment when high latitudes were under ice-free conditions. All Arctic plant fossils in this research are conifers, plants conducive for morphological and molecular study because of their incredible genetic stability. Miocene (15 million year old) and Pliocene (5 million year old) conifer leaves were collected from Banks Island, Canada (Williams et al., 2008). Samples were analyzed and compared with Paleocene (60 million year old) and Eocene (45 million year old) samples from Axel Heiberg Island, Canada and with modern equivalent species from Washington D.C., USA (William et al., 2008). This paper has three main sample analyses. First, Pyrolysis-Mass Spectrometry-Gas Chromatography technology was used to detect organic volatile compounds. The amounts and types of organic volatile compounds provide further insights into the molecular preservation of the Miocene and Pliocene fossilized samples. Molecular preservation from this research was compared to previous research that used Scanning Electron Microscope observations of Paleocene and Eocene transverse sections to indicate extraordinary morphological preservation (Yang et al., 2005; Yang et al., 2007). Second, Miocene and Pliocene bulk peat were cross-referenced with known species in the region to reconstruct Arctic environmental changes between 5 million and 15 million years ago. Third, the ratios of three stable compounds were analyzed as biomarkers, essentially benchmarks for plant fossil preservation. However, biomarkers were inconclusive because of complications including age, species type, and environmental conditions. Overall, our analyses provide the first assessments of molecular preservation for these rare Arctic fossils which offer unique material for further paleoclimate analysis

Trialkylphosphine-mediated synthesis of 2-Acyl furans from ynenones

A novel reaction for the synthesis of 2-acyl furans is reported. The reaction is believed to proceed by sequential addition of a trialkylphosphine to an ynenone, 5-exo-dig cyclization to form the furan, and oxidation of the resulting phosphonium ylide with molecular oxygen. Many common functional groups are tolerated during the reaction, and the products are obtained in good to excellent yield under the mild conditions. This methodology offers efficient access to biologically important compounds, including fused polycyclic compounds and furaldehydes, from simple starting materials