Computational investigation of a stereoselective synthesis of atropisomeric hydrazides possessing an N–N stereogenic axis

Axially chiral substrates are an interesting and widely studied class of compounds as they can be found in bioactive natural products and are employed as functional materials or as ligands in asymmetric catalytic processes. One branch of this family is the well-known world of the atropisomers. Among them, atropisomeric compounds possessing an N–N stereogenic axis are one truthfully fascinating system but not completely understood yet. In this thesis, we computationally investigated the mechanism of the diastereoselective formation of the N – N chiral axis of a hydrazide under asymmetric phase transfer catalytic conditions. Moreover, during this study, torsional barriers have been calculated for both the reagent and the product at the density functional theory (DFT). These values turned out to suitably match the experimental values and observations. Finally, Electronic Circular Dichroism (ECD) spectra have been simulated in order to assign the chiral absolute configuration to the products.

Sviluppo di un metodo termoanalitico per la quantificazione di microplastiche in matrici complesse

Microplastics (MPs) are highly debated emerging contaminants that are widespread on Earth. Nowadays, assessment of the risk that MPs pose on human health and environment were not developed yet, and standardized analytical methods for their quantification in complex matrices do not exist. Therefore, the formulation of standards which regulating MPs emission in the environment is not possible. The purpose of this study was to develop and apply a method for the analysis of MPs in sewage sludges and water from a wastewater treatment plant (WWTP), due to the relevance of those matrices as important pathway for MPs to enter the environment. Seven polymers were selected, because of their relevance on market production and their frequency of occurrence in such plants: polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyvinyl chloride (PVC), and nylon 6 (PA-6). In the study, a pre-treatment procedure was optimised using Fenton’s reagent and analyses carried out by combining thermochemolysis with Py-GC-MS after sample filtration on quartz (0.3 µm). Polymer quantification was performed with solid polymer mixture in silica and good correlations were obtained with internal calibration. As main results, Fenton's reagent negatively affected the recovery of some polymers (PP, PE, PS, PA-6) and a possible matrix interference was noticed, especially for PET and PVC. The WWTP allowed a good abatement of PS, PE, PP and PVC (on average 90 %) and comparable results were hypothesised for the other polymers. Polymer concentrations is sewage sludges ranged between < 2 μg/gdry and 3.5 mg/ gdry, for PC and PVC, respectively. Possible overestimations for PET and PVC, due to matrix interreferences, were taken into account and discussed.