Infrared and Raman spectroscopic studies of matrix isolated amines

Purnell, CJ

Abstract

This thesis describes the infrared and Raman spectroscopic studies on ammonia, methylamine and ethylamine in low temperature argon and nitrogen matrices.
The initial aim was to classify qualitatively and quantitatively the matrix isolated spectra of these molecules and subsequently to evaluate whether the method would prove sufficiently sensitive for the subsequent analysis of these malodorous substances in polluted atmospheres, and to compare the results with those already available from gas liquid chromatography and mass spectrometry. These results are discussed in chapter 8.
In practice anomalous intensity variations were discovered in the spectrum of methylamine (chapter 4) which complicated the quantitative work. No such intensity variations were observed for ethylamine or ammonia (chapters 6 and 7). The abnormalities justified a thorough infrared and Raman spectroscopic analysis of the three molecules.
Chapter 1 gives an outline of the project and introduces the matrix isolation technique.
Chapters 2 and 3 deal with the experimental techniques employed for the infrared and Raman spectroscopic studies along with additional data analysing techniques.
Chapter 4 presents the results and a complete spectral assignment for methylamine and methylamine-d2. These results are used in a normal coordinate analysis (chapter 5). The resulting force field is used to predict the spectrum of the methylarrdne-d^ molecule, enabling a more positive assignment to be made for the
previously unobserved NI^ and ND2 twisting frequencies.
In chapter 6 information concerning the conformational isomerism of ethylamine is obtained. Although there is some conflict between the infrared and Raman results for the CCN symmetric stretching vibration, the evidence is generally in favour of both conformers being present in argon and only the more stable trans conformer in nitrogen.
The spectroscopic studies of ammonia in argon and nitrogen matrices are presented in chapter 7. Agreement is obtained with previous work for the argon matrix in the infrared, namely that the temperature dependence of the bands could be explained as being due to the rotational freedom of the molecule in the substitutional site. However, the Raman results are completely incompatible with the theory that relatively free rotation in the matrix site is occurring. Using a group theoretical treatment the results are explained, at least qualitatively, as due to a constrained orientational motion rather than a rotational one.
Further information was obtained concerning the dimer species of ammonia in the matrices. The evidence leads to the conclusion that the open chain dimer predominates in the argon matrix but that both open chain and cyclic dimers are present in reasonable quantities in the nitrogen matrix. A detailed assignment of the open chain dimer frequencies is presented.

Citation

Purnell, C. Infrared and Raman spectroscopic studies of matrix isolated amines. (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Nov 4, 2021
• Publicly Available Date: Nov 4, 2021
• Publisher URL: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.469631
• Related Public URLs: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.469631
• Award Date: Nov 1, 1974