Molecular Studies in the Gas Phase by Microwave Spectroscopy

MacDonald, John N (1969) Molecular Studies in the Gas Phase by Microwave Spectroscopy. PhD thesis, University of Glasgow.

Abstract

In this thesis an account is given of studies of the rotational spectra of gamma-Pyrone, thiapyrone, cyanamide, nitramide, dideuterocyanamide and aminoacetonitrile. The spectra of these compounds were studied in the Stark modulation spectrometer which is described briefly in the introductory chapter. gamma-Pyrone and thiapyrone were studied as part of an investigation of the molecular geometries of compounds belonging to the gamma-Pyrone series. Five isotopic species of gamma-Pyrone and the normal species of thiapyrone have been studied. It is concluded that both molecules are planar structures in the ground vibrational state and that there is some evidence of angular distortion of the rings to accommodate the heteroatoms in a planar structure. The Stark effect of gamma-Pyrone has been found to be non-quadratic and a special treatment of the Stark effect has been carried out enabling the dipole moment of the molecule to be obtained. A study has been made of 14N-quadrupole coupling in thespectra of cyanamide and nitramide and the coupling constants obtained for these molecules. Conclusions are drawnregarding the delocalisation of the lone-pair electrons of theamino nitrogen atom into the pi-systems of the molecules. An extrapolation of these results to the more general NH2, X system (X an electron withdrawing group) is suggested. The energy levels of dideuterocyanamide are highly perturbed by vibration/rotation interactions. It has been possible to locate the K -1 =2 rotational energy levels of the ground vibrational state relative to the K-1 = 1 levels of the first excited state. It is concluded that second order perturbation theory is insufficient for the calculation of these energy levels and that a more complete calculation is required. Some preliminary conclusions about the structure of aminoacetonitrile have been obtained. Three species have been studied and the amino hydrogen atom coordinates located exactly by isotopic substitution. The molecule exists in the conformation with the amino hydrogen atoms trans to those of the methylene group.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Physical chemistry, Molecular chemistry
• Date of Award: 1969
• Depositing User: Enlighten Team
• Unique ID: glathesis:1969-78517
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 30 Jan 2020 15:12
• Last Modified: 30 Jan 2020 15:12
• URI: https://theses.gla.ac.uk/id/eprint/78517