Study of catalytic reactions by action spectroscopy and ionic mobility coupled by mass spectrometry

The study of different cyclization reactions using mass spectrometry coupled with isomer identification methods such as infrared vibrational ion spectroscopy (IRMPD) and ion mobility will be discussed in this thesis. There are several types of reactions of commercial and synthetic interest need to have their mechanisms elucidated, especially cyclization reactions. In this thesis we discuss in a deeper level the nature of the isomeric species formed during the reactions, which is difficult to characterize by customary mass spectrometry techniques. The first system studied was the synthesis of the benzoxazine monomer (3,4-dihydro-2H-phenyl-1,3-benzoxazine) in order to clarify the preferencial reaction pathways (including the role of acid catalysis) through the identification of its reaction intermediates and by-products. This is relevant given that the performance of polybezoxazine resins depends directly on the stage of production of its monomer. The second system studied was the intramolecular bromoamination cyclization reactions promoted both by organocatalysts derived from thiourea and quinidine, and by metallic Pd/Cu catalysts. For this purpose, real-time direct sampling methods were used, allowing that even reactions in complex matrices, such as those carried out with high loads of salts and ligands, to be studied by mass spectrometry. From a theoretical point of view, conformational search methods followed by electronic structure calculations were used to elucidate the acquired IRMPD vibrational spectra and the energy profile of the reactions, in addition to methods for calculating the collisional cross sections for direct comparison with data from ion mobility measurements. With the development of this proposal, it was possible to contribute to the understanding of the catalytic cycles of these important reactions, which can lead to the development of new catalysts and reaction conditions with significant improvements in the performance of these reactions, in addition to paving the way for the study of other chemical and biological system by the techniques used here. (AU)