Uso da técnica de espectrometria de massas com ionização por eletrospray (ESI-MS) para o estudo do mecanismo de reações orgânicas e avaliação do perfil de fragmentação de bis-hidroxiiminas aromáticas

Abstract

Electrospray Ionization Mass Spectrometry (ESI-MS) was applied to investigate the mechanism of two organic reactions: Zincke and Aza Diels Alder. A systematic study regarding the fragmentation of typical Salophen ligands (bis-hydroxy-imine) in their protonated forms was also conducted. In the Zincke reaction monitoring it was observed, besides the traditional products, novel intermediates whose structures were proposed based on their fragmentation profiles obtained by MS/MS experiments. All these intermediates were detected in reactions performed with four different amines: 2-amino-1,3-propanediol, alfa-methyl-benzyl, amino-1-propanol, and alfa-phenyl-glicinol. These results were therefore important to confirm the mechanism proposed in literature for this reaction. In the tri component Aza Diels Alder reaction, conducted in three different solvents (acetonitrile, ethanol, and methanol), the ESI-MS (and MS/MS) data provided solid evidence that this process proceeds via a non-concerted mechanism also proposed in literature. Finally, it was observed that the protonated forms of the several Salophen ligands fragmented to yield distinct product ions. The different relative positions of the substituents (hydroxyl and imino groups) in the benzene rings of such molecules were ascribed to play a major role in the distinct fragmentation profiles observed.