Evaluation of reaction intermediates by gas phase spectroscopy and ion mobility

Abstract

This proposal requests funding for the Ph.D. candidate to conduct predissociation ion spectroscopy and ion mobility experiments in Prof. Gert von Helden's group in the Fritz Haber Institute (Germany), so a comprehensive evaluation of reaction intermediates, a central point to the candidate thesis project, can be achieved in a way that is not possible using the techniques available in our home institution or many other institutions worldwide. The main objective of this Ph.D. project is to evaluate the synthetic relevant reaction intermediates of organometallic mediated reactions, as the Ti based epoxidation (Katsuki-Sharpless reaction) and Pd/Cu mediated carbamate cyclization reactions. To evaluate these reactions by mass spectrometry, not only alternative ways to sample and to promote chemical reactions need to be developed, but other techniques must be used to allow the complete characterization of the isomeric reactive species present in the reaction media, like ion spectroscopy and ion mobility. The Ph.D. candidate overcame the first part of these challenges by implementing experimental techniques to sample reaction media that are incompatible to standard ESI experiments, including the use of multiple sprays, online derivatization, and desorption electrospray ionization sources. In that context, the intermediates of the Sharpless epoxidation reaction were successfully observed and the intermediates are currently being evaluated. This appointment abroad will allow cryogenic infrared predissociation spectroscopy of ion mobility selected ions to be carried out, allowing the evaluation of the exact nature of the intermediates observed in our research group. This will extend the spectral region and resolution in comparison to the instrumentation available in our group and would also allow the Ph.D. candidate to acquire experience on the ion mobility separation by mass spectrometry, a technique that will be implemented in our research group in Brazil in the near future. Therefore, this appointment will be instrumental in the conclusion of the Ph.D. thesis of the candidate and will allow new skills to be developed, supporting the research projects carried out in our research group - specially upon his return - and fostering collaborations between institutions. (AU)