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Title: Far infrared studies relating to the origin of torsional barriers
Author: Campagnaro, Gastone Ennio Massimiliano Luigi
Awarding Body: University of London
Current Institution: Imperial College London
Date of Award: 1968
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Theories of the origin of barriers to internal rotation are reviewed and methods of determining barrier heights are briefly discussed. Minor modifications to the far-infrared spectrometer designed and constructed in the department have improved its performance, especially below 110 cm-1 where the filtering was inadequate. The torsional frequency of acetaldehyde in the gas state is assigned to 143 cm-1. The corresponding triple cosine barrier shows a discrepancy of 68 cal/mole compared with the microwave value. Both results are based on the same theory for the energy levels and the same reduced moment of inertia. The discrepancy is ascribed primarily to the uncertainty in the reduced moment of inertia. Using both infrared and microwave data, a more reliable value of V3 is calculated to be 1128 cal/mole. All features of the high frequency spectra of acrolein and butadiene can be accounted for on the basis of a single isomer, the rotational fine structure being characteristic of the trans form. The sub-bands of the torsional frequency of acrolein have been resolved. The marked degradation indicates a change of about 2.7% in the rotational constant A in the first torsionally excited state. This results in the R branch being considerably more intense than the P branch. Some further contribution to the R branch intensity is considered to be due to the difference band V - V18 enhanced by Fermi resonance, V13 with 2V 18. The torsional band of butadiene could not be resolved in the same manner. Potential functions to internal rotation which might be expected for, the molecules are discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available