LC-MS ion maps for the characterization of aniline derivatives of fatty acids and triglycerides in laboratory-denatured rapeseed oil

In 1981 Spain went through a unique epidemic associated with a food-borne vector, affecting more than 20,000 people with over 800 deaths, which came to be known as the Toxic Oil Syndrome (TOS). Early epidemiological studies showed a link between this illness and the ingestion of rapeseed oil denatured with 2% aniline. This oil, originally aniline-denatured for industrial use, was fraudulently processed in an attempt to remove free aniline, and marketed as edible oil. Fatty acid anilides (FAA), monoesters and diesters of 3-(N-phenylamino)-1,2-propanediol (PAP) are present in oil samples as they arise in the refining process from reactions of aniline with constituent fatty acids and triglycerides of the oil matrix and are the only extraneous compounds found in these samples. To expand the search for the causative agents in TOS-associated oils and to look for new aniline-related compounds, an exhaustive characterization of laboratory-processed oils was undertaken. These oils, in the presence of aniline doped with 14C labelled aniline, were submitted to the laboratory conditions required for the generation of PAPs and FAAs. Laboratory-generated oil samples were submitted to a liquid-liquid extraction procedure to remove the unreacted aniline. The extract was processed by double solid-phase extraction to improve detection limits for minor amine-containing compounds in oils. The extracts enriched in aniline derivatives were submitted to on-line HPLC-UV-APCI-MS. Using two-dimensional ion maps, the components of several families of derivatives were readily identified. Additionally, the extracts were also fractionated by HPLC-UV and the fractions were analyzed by HPLC-APCI-MS/MS to obtain structural information. Standards of some of these compounds were synthesized and analyzed to confirm the results. A total of 115 aniline derivatives from 9 aniline-related families were identified in these oil samples. These included fatty acid anilides and an extensive array of phenylaminopropanediol esters distributed in eight major compound classes.     

Direct-dynamics VTST study of the [1,7] hydrogen shift in 7-methylocta-1,3(Z),5(Z)-triene. A model system for the hydrogen transfer reaction in previtamin D3

Direct-dynamics canonical variational transition-state theory calculations with microcanonically optimized multidimensional transmission coefficient (CVT/muOMT) for tunneling were carried out at the MPWB1K/6-31+G(d,p) level to study the [1,7] sigmatropic hydrogen rearrangement in 7-methylocta-1,3(Z),5(Z)-triene. This compound has seven conformers, of which only one leads to products, although all of them have to be included in the theoretical treatment. The calculated CVT/muOMT rate constants are in good agreement with the available experimental data. To try to understand the role of tunneling in the hydrogen shift reaction, we have also calculated the thermal rate constants for the monodeuterated compound in the interval T = 333.2-388.2 K. This allowed us to evaluate primary kinetic isotope effects (KIEs) and make a direct comparison with the experiment. Our calculations show that both the large measured KIE and the large measured difference in the activation energies between the deuterated and root compounds are due to the quantum tunneling. The tunneling contribution to the KIE becomes noticeable only when the coupling between the reaction coordinate and the transverse modes is taken into account. Our results confirm previous experimental and theoretical works, which guessed that the obtained kinetic parameters pointed to a reaction with an important contribution due to tunneling. The above conclusion would be essentially valid for the case of the [1,7] hydrogen shift in previtamin D3 because of the similarity to the studied model system.     

Metal-Organic Frameworks as Unique Platforms to Gain Insight of σ-Hole Interactions for the Removal of Organic Dyes from Aquatic Ecosystems

The combination of high crystallinity and rich host-guest chemistry in metal-organic frameworks (MOFs), have situated them in an advantageous position, with respect to traditional porous materials, to gain insight on specific weak noncovalent supramolecular interactions. In particular, sulfur σ-hole interactions are known to play a key role in the biological activity of living beings as well as on relevant molecular recognitions processes. However, so far, they have been barely explored. Here, we describe both how the combination of the intrinsic features of MOFs, especially the possibility of using single-crystal X-ray crystallography (SCXRD), can be an extremely valuable tool to gain insight on sulfur σ-hole interactions, and how their rational exploitation can be enormously useful in the efficient removal of harmful organic molecules from aquatic ecosystems. Thus, we have used a MOF, prepared from the amino acid L-methionine and possessing channels decorated with −CH₂CH₂SCH₃ thioalkyl chains, to remove a family of organic dyes at very low concentrations (10 ppm) from water. This MOF is able to efficiently capture the four dyes in a very fast manner, reaching within five minutes nearly the maximum removal. Remarkably, the crystal structure of the different organic dyes within MOFs channels could be determined by SCXRD. This has enabled us to directly visualize the important role sulfur σ-hole interactions play on the removal of organic dyes from aqueous solutions, representing one of the first studies on the rational exploitation of σ-hole interactions for water remediation.     

Synthesis,Characterization, and Thermal Behavior of Carboranyl–Styrene Decorated Octasilsesquioxanes: Influence of the Carborane Clusters on Photoluminescence

Novel polyhedral oligomeric silsesquioxanes (POSS) or octasilsesquioxanes with carboranyl–styrene fragments attached to each corner are described. These compounds have been synthesized by olefin‐metathesis reactions between octavinylsilsesquioxane and carboranyl–styrene compounds that possess different substituents (Ph, Me, or H). In all cases, these reactions, which were catalyzed by the Grubbs catalyst, are highly regioselective and yield exclusively the E isomers. The existence of the carborane cage in the POSS structure induces a remarkable thermal stability in these compounds. After combustion at 1000 °C, these carboranyl–POSS compounds exhibit a mass loss lower than 10 %. The UV/Vis absorption data of these carboranyl–POSS compounds shows a slight bathochromic shift with respect to the carboranyl–styrene monomers, with an absorption maximum around 262 nm. Nevertheless, important differences in the emission spectra of the carboranyl–POSS compounds with regard to their carboranyl–styrene precursors are observed; the phenyl‐o‐carborane‐containing POSS compound exhibits the highest fluorescence intensity (Φ_F=44 %), whereas for the POSS compound bearing the methyl substituent, and for the unsubstituted o‐carborane clusters, the fluorescence intensity is much lower (Φ_F=9 and 2 %, respectively). This is precisely the reverse of what occurs with the monomers, in which the unsubstituted o‐carboranyl–styrene compound exhibits the highest Φ_F, and a quenching of the fluorescence is observed in the phenyl‐o‐carboranyl–styrene compound. In addition, a large red shift of around 100 nm is observed for the POSS compounds with respect to their precursors. These experimental results can only be accounted for by the spatial ordering induced by the POSS core that eases interactions, which otherwise would not occur. These results have been confirmed by time‐dependent density functional theory (TDDFT) calculations that exclude a photoinduced electron transfer (PET) process in the POSS compounds.     

Investigating adsorption of bovine serum albumin on cellulosic substrates using magnetic resonance imaging

Cellulosic biomass is recalcitrant to enzymatic hydrolysis which greatly reduces the efficiency of biofuels production. Specifically, the lignin component of biomass is thought to provide non-productive binding sites for glycosyl hydrolases, effectively disabling the enzymes from completing further digestion. A thorough understanding of the adsorption rates of protein molecules on celluloses—especially lignocelluloses—is crucial to improving the cyclic steps of adsorption, diffusion, and reaction. We use magnetic resonance imaging (MRI) to detect concentrations of bovine serum albumin (BSA) in equilibrium with various cellulose substrates, including delignified and acid-treated lignocellulosic substrates. BSA is believed to be an effective adsorption blocker during enzymatic hydrolysis of lignocellulosics, and has been correlated with an increase in reaction yield. We found BSA to have little adsorption onto the chosen cellulose substrates in the low concentration range studied. Ultraviolet (UV) absorption measurements of reaction supernatants at 280 nm were used to confirm the MRI results for each of the substrate types. The advantages of the MRI technique are compared with that of the traditional UV measurement.     

Electrolytic synthesis of chloroacetic acids in a filter-press reactor from polychloromethanes

Electrochemical carboxylation of carbon tetrachloride and chloroform to synthesize chloroacetic acids in mild conditions has been investigated by galvanostatic electrolyses using a homemade electrochemical filter-press reactor. Undivided filter-press reactor consisting of a planar Zn cathode and a planar Al sacrificial anode has been shown to be an optimal electrochemical device for the electrocarboxylation reaction. The influence of some operative parameters, such as current density and concentration of supporting electrolyte, on the efficiency and selectivity of the synthetic process has been investigated. Highly current efficiencies and target products yields (both of them > 85%) were achieved in all cases, whereas byproducts formation was minimal.     

The Use of Transplanted Venerupis Decussata to Evaluate the Pollution of Heavy Metals and Tributyltin in Marinas

Abstract

Live specimens of the clam Venerupis decussata were suspended in seawater of the Mazagon Marina, located in a heavy metal polluted area at the mouth of Huelva Estuary (SW Spain), Clams were preserved in plastic cages and subsamples were recovered every 5 days over a period of 40 days. Water from the marina was sampled every two days during the time course of the experiment. Clams and water were analyzed for metals and organotins. Results showed the accumulation of Mn, Cu, Fe, V, Zn and tributyltin in the bivalves reaching an equilibrium with the surrounding water. Bioconcentration factors ranged from 10² (for V) to 4×10³ (for Cu). Clams also accumulated Al and Pb but a steady state was not reached. A first-order kinetic model was applied to the data and results indicated that rates of accumulation differed in relation to clam size class. Clam mortality increased during the experiment and was total after 42 days which was attributed to the high concentration of Cu in seawater.