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Gas phase studies of small hydrocarbons, organometallic complexes, and nucleic acids by use of tandem and Fourier transform mass spectrometry
Abstract
The scope of this dissertation involves the utilization of mass spectrometry for studying the chemistry of gas-phase ions. Specifically, tandem (MS/MS) and Fourier transform mass spectrometry (FTMS) are used to investigate the ion chemistry of small unsaturated hydrocarbons, methinyltricobalt enneacarbonyls, and small oligonucleotides. The first and second chapters focus on the study of ion-molecule reactions in mixed systems of propene or cyclopropane and ethylene. By utilizing a high-pressure source coupled to a tandem mass spectrometer, these reactions produce stable C$\sb5$H$\sb{10}$ adduct ions. The structure of the adducts are elucidated by comparing their collisional-activation decomposition and charge-stripping spectra with those of C$\sb5$H$\sb{10}$ reference compounds. Additionally, FTMS is used to establish the ionic and neutral reactants and to determine the rates of reaction. The reactions were further investigated by incorporating an rf-only-mode event in the FTMS experiment. The rf-only-mode event enabled the production of stable C$\sb5$H$\sb{10}$ adducts and subsequent investigations of their bimolecular reactivity. The third chapter describes the study of the radical cation rearrangement of 4-vinylcyclohexene to bicyclo (3.2.1) -2-octene. This rearrangement is observed to occur spontaneously without collisional stabilization, but it can be controlled with the addition of bath gas in the sector mass spectrometer or by the addition of an rf-only-mode event in the FTMS experiment. The fourth chapter involves the investigation of the reactivity of methinyltricobalt enneacarbonyl radical anions by MS/MS and by FTMS. The unimolecular and bimolecular reactivity of these compounds varies with their apical substituent. The results suggest that electron density is delocalized throughout the ion and the extent of delocalization is dependent on the apical substituent. The focus of Chapters 5, 6, and 7 is the study of small oligonucleotides by fast atom bombardment (FAB). By adding a cation-exchange resin to the FAB matrix, metal cations can be either removed from or incorporated into the nucleotide sample. The method of alkali cation removal gives superior results to those of other removal methods. Up to four metal ions can be incorporated into a trinucleotide by using a metal-exchange resin. The sites of cationization can be determined by observing their unimolecular chemistry. Isomeric-hexanucleotide photoadducts were also studied by using FAB and MS/MS. The unimolecular chemistry of these compounds gives information as to which adjacent bases are photoattached and to the position of attachment.
Subject Area
Analytical chemistry|Biochemistry|Chemistry
Recommended Citation
Vollmer, David Lee, "Gas phase studies of small hydrocarbons, organometallic complexes, and nucleic acids by use of tandem and Fourier transform mass spectrometry" (1994). ETD collection for University of Nebraska-Lincoln. AAI9507831.
https://digitalcommons.unl.edu/dissertations/AAI9507831