DTIMS collision cross section database for metabolites and xenobiotics.

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Polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are persistent environmental pollutants originating from incomplete combustion of organic materials and synthetic sources. PAHs, PCBs, and PBDEs have all been shown to have a significant effect on human health with correlations to cancer and other diseases. Therefore, measuring the presence of these xenobiotics in the environment and human body is imperative for assessing their health risks. To date, their analyses require both gas chromatography and liquid chromatography separations in conjunction with mass spectrometry measurements for detection of both the parent molecules and their hydroxylated metabolites, making their studies extremely time consuming. In this work, we characterized PAHs, PCBs, PBDEs and their hydroxylated metabolites using ion mobility spectrometry coupled with mass spectrometry (IMS-MS) and in combination with different ionization methods including electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI). The collision cross section and m/z trend lines derived from the IMS-MS analyses displayed distinct trends for each molecule type. Additionally, the rapid isomeric and molecular separations possible with IMS-MS showed great promise for quickly distinguishing the parent and metabolized PAH, PCB, and PDBE molecules in complex environmental and biological samples.

The AgSbF-catalyzed cyclization of 2-diazo-3,5-dioxo-6-ynoates (ynones, ynamide) in alcoholic solvents affords γ-pyrones, whereas the AgOAc-catalyzed cyclization in 1,2-dichloroethane (DCE) produces 3(2H)-furanones. The cyclization reactions proceeded cleanly under mild reaction conditions, and the desired γ-pyrones or 3(2H)-furanones were obtained in excellent yield. It was observed for the first time that both the catalyst and solvent play key roles in the selective formation. This unique method for the reversal of regioselectivity proved to be highly efficient except for substrates with aliphatic and MeSi groups at the triple bond position.

This tutorial review provides an outline of basic concepts, historical milestones and recent advances in main group metal catalysed olefin polymerisation and ring-opening (co)polymerisation reactions.

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Seven lithium complexes supported by sterically and electronically diverse phenoxyimine ligands were synthesized and characterized by X-ray diffraction, NMR spectroscopy and elemental microanalysis. These complexes show high activity (k obs � 7.43 × 10 À 2 s À 1 ) for rac-lactide ring-opening polymerization (ROP) in the presence of co-initiator benzyl alcohol (BnOH), with the exception of Li4 which features an unusual polymeric ladder structure. Overall, the catalyst activity correlates to the aggregation state; the catalysts with low aggregation states display increased propagation rates attributed to improved metal accessibility and kinetic mobility. The nature of the ligand substituents and solvent influence the catalyst aggregation in both the solid-and solution-state. While the lithium complexes can initiate rac-lactide ROP without BnOH, the addition of this co-initiator significantly increases the polymerization rate by switching the mechanism from a coordination-insertion to an activated monomer pathway, changing the resultant poly(lactic acid) architecture from cyclic to linear.