Microwave Spectral Studies on Aniline and Some Other Molecules

Lister, David G (1968) Microwave Spectral Studies on Aniline and Some Other Molecules. PhD thesis, University of Glasgow.

Abstract

This thesis contains an account of microwave spectral studies aniline, propiolic acid, 2,1,3-benzoxadiazole and 2,1,3-benzothiadiazole, and glycollonitrile. All of the spectra were observed at room temperature using a conventional Stark modulation spectrometer. A brief description of the spectrometer, the method used to calculate rigid asymmetric top energy levels and the location of atoms in a molecule are given in Chapter 1. Chapters 2-5 devoted to the spectral studies on the molecules mentioned above and Chapter 6 contains details of the preparation of a number of these compounds. The microwave spectra of ten isotopic species of aniline have been observed and transitions due to molecules in the ground and a very low first excited vibrational state have been assigned. A low first excited vibrational state is characteristic of a pyrimidal configuration about the nitrogen atom and an inverting amine group. The inertial defects, and substitution co-ordinates of the amino-hydrogen atoms confirm that aniline is non-planar and an rs structure has been derived for the C-NH2 group. The co-ordinates of the ring hydrogen atoms in aniline indicate that the phenyl group is somewhat narrower and elongated compared to benzene. Three species of propiolic acid have been studied and the planar nature and cis conformation of the hydroxyl relative to the carbonyl group in this molecule are confirmed. Allowance has been made for centrifugal distortion in deriving the rotational constants, but it is impossible to derive accurate values for the centrifugal distortion constants from the measured line frequencies. The dipole moment of propiolic acid has been obtained from Stark effect measurements and lies almost parallel to the direction of the C = O bond. The spectra of the normal isotopic species of 2,1,3-benzoxadiazole and 2,1,3-benzothiadiazole have been assigned and the inertial defects indicate that these molecules are planar. Structures with considerable double bond fixation in the six membered rings are proposed for these molecules. Some preliminary conclusions about the structure of glycollonitrile are given in chapter 5. Spectra of the normal and one deuterated species (DOCH2CN) have been assigned. The inertial defects of these molecules and the substitution co-ordinates of the hydroxyl hydrogen atom show that glycollonitrile exists in the gauche form.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Organic chemistry, Analytical chemistry, Molecular chemistry
• Date of Award: 1968
• Depositing User: Enlighten Team
• Unique ID: glathesis:1968-78492
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 30 Jan 2020 15:15
• Last Modified: 30 Jan 2020 15:15
• URI: https://theses.gla.ac.uk/id/eprint/78492