Mass spectrometry, mechanisms, and molecular models - combining research in mass spectrometric reaction monitoring and chemical education

Date

2018-05-18

Authors

Dean, Natalie L.

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Abstract

This thesis combines work in the areas of mass spectrometric reaction monitoring and chemical education. In the first part of this thesis, real-time mechanistic analysis using electrospray ionization mass spectrometry is reported. In Chapter 1, an introduction to the mass spectrometric instrumentation and methodologies used in this research is provided. In Chapter 2, the real-time mechanistic analysis of the Hiyama cross-coupling reaction using electrospray ionization mass spectrometry is reported, in particular, the fluoride-mediated rearrangement of phenylfluorosilanes that was found to occur even before catalyst addition. Combining Ph3SiF with a fluoride ion source under typical Hiyama cross-coupling conditions causes rapid formation of the expected [Ph3SiF2]–; however, ESI-MS analysis reveals that phenyl-fluoride exchange occurs concomitantly, also producing substantial quantities of [PhnSiF5–n]– (n = 0-2). The exchange process is verified using 19F NMR spectroscopy. This observation may have implications for Hiyama reaction protocols, which use transmetallation from triaryldifluorosilicates as a key step in cross-coupling. Optimization of the methodology used for real-time analysis by ESI-MS to reduce observed contamination from leaching of rubber septa additives is also discussed. In the second part of this thesis, the development and application of two different approaches for generating molecular models for the teaching molecular geometry and VSEPR theory in first year chemistry is reported. Chapter 4 details a method for the application of handheld 3D printing pens for producing models from ABS plastic. In Chapter 5, the development of laser-cut acrylic model kits is detailed, as well as the design and results of a quantitative study aimed at assessing their effectiveness for improving representational competence and comprehension of molecular geometry.

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Keywords

Mass Spectrometry, Chemical Education, VSEPR, Hiyama Cross-Coupling, Fluorophenylsilane, Molecular Geometry

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