Exploring the Chemistry of Methoxide with Oxygen through Photoelectron Imaging Spectroscopy

Abstract

In this dissertation, photoelectron imaging spectroscopy is employed to probe the gas-phase chemistry between methoxide (CH3O) and oxygen, including evidence of previously unexplored reaction paths and providing further insight into the fundamentals of chemical bonding. First, the known reaction of CH3O and O2 to produce the hydroperoxide anion (HO2) is leveraged to investigate the photoelectron angular distributions as a function of electron kinetic energy, corresponding to photodetachment to each the ground X 2A′′ and excited A 2A′ electronic states of the neutral HO2 radical. These are modeled with the p-d variant of the generalized mixed-character model, and the results are compared to O2 and NO to gain insights into the effect on electronic structure of the breaking of molecular symmetry through the addition of a new bond. The results are also compared to predictions based on the qualitative s&p symmetry model—which reduces the properties of a molecular orbital to its symmetry character only—in order to further elucidate the role of symmetry in photoelectron angular distributions. Second, evidence of novel chemistry between methoxide and oxygen is presented, as the photoelectron spectrum corresponding to detachment from the formate anion (CHO2) is reported. The agreement of both the spectral information and the photoelectron angular distribution with previous work done on the system confirms the identity of the anion, and introduces evidence of previously unknown chemistry by which CHO2 is formed by a reaction between CH3Oand O2. Finally, further evidence of this novel chemistry is explored through interrogation of the anionic species which appeared in the mass spectrum at a mass-to-charge ratio of 63 amu, corresponding to a molecular formula of CH3O3. The identity of this molecule is not unambiguously assigned in this work, but 22 the existence of a bound structure with this molecular formula consequent of the interaction between methoxide and oxygen provides significant insight into an otherwise unknown reaction path. Future directions both to build on this work and to improve of the experimental apparatus are presented in the final chapter.