Studies of the kinetics of ion-molecule reactions associated with isobutane chemical-ionization mass spectrometry have shown that many of these reactions proceed via the formation of a collision complex which undergoes either unimolecular decomposition to reactants, or collision-induced decomposition to products. Rate constants for the formation of collision complexes between isobutane reactant ions and various ketones, nitriles, alcohols, and anisoles were obtained. Comparisons between these rate constants and collision frequencies calculated from the Average-Dipole-Orientation theory showed that, in general, the reactions proceeded with efficiencies less than unity. The lifetimes of most of the collision complexes were found to lie in the range 1-10 Psec. The relative efficiencies with which several compounds effected the collision-induced decomposition of the complex suggested that the third-body efficiencies were determined by the collision duration. Charge - transfer reactions between the isobutane reactant ions and anisoles occur by a direct mechanism. The magnitude of the rate constants for the formation of collision complexes were related to the structures of the compounds under study. For the reactions of certain reactant ions with the anisoles and halohydrins the rate constants were correlated with the appropriate substituent constants. It was suggested that differences between the mechanism proposed herein and that proposed by Field for the reaction between C4Hg+ and benzyl acetate were due to differences in sample-pressure ranges. Kinetic studies of the ion-molecule reactions consequent upon electron-impact ionization of methane and of isobutane, have suggested a novel method of estimation of reagent-gas pressures.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:476244 |
| Date | January 1979 |
| Creators | Walder, R. |
| Publisher | Royal Holloway, University of London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://repository.royalholloway.ac.uk/items/547c23ef-b015-418d-8226-1a3447f8df14/1/ |
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