| dc.contributor.author | Mothana, Belquis. | en_US |
| dc.date.accessioned | 2014-10-21T12:33:34Z | |
| dc.date.available | 2007 | |
| dc.date.issued | 2007 | en_US |
| dc.identifier.other | AAINR27200 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/54908 | |
| dc.description | The pyrrole heterocycle is an important component of many biological molecules and a key aspect of many synthetic pathways. It is incorporated as a fundamental substructure in a tremendous range of natural products and bioactive molecules; hence the study of the chemistry of pyrroles is of great interest. Computational methods provide a powerful tool for exploring reaction mechanisms, potential energy surfaces, excitation energies and the prediction of many properties of molecules and reactions. Such methods complement experimental results, and provide an insight that is not possible otherwise. | en_US |
| dc.description | This thesis describes the application of density functional theory to the prediction of nuclear magnetic resonance (NMR) properties of pyrroles and a study of several reaction mechanisms of pyrrole synthesis. In the first part of the thesis, a valid computational scheme for the study of the 15N and 13C NMR properties of nitrogen-containing molecules is provided. The computational scheme is used to elucidate the relationship between electron-withdrawing groups on the nitrogen atom of pyrroles and their 15N and 13C NMR parameters. A correlation between the paramagnetic shift and the 15N chemical shift of N -substituted pyrroles indicates that the experimentally observed 15N chemical shift trend arises entirely from variations of the paramagnetic shift contribution to the chemical shift. The second part of the thesis concentrates on selected reaction mechanisms of pyrrole synthesis to provide insight into the biosynthesis of the porphobilinogen (PBG) pyrrole. In particular, the Paal-Knorr and Knorr pyrrole synthesis mechanisms are investigated. The preferred mechanisms are identified on the basis of computed potential energy surfaces for possible reaction pathways. The present results suggest that the hemiaminal cyclization is the preferred pathway for the Paal-Knorr pyrrole synthesis and that the enamine cyclization is the preferred step for the Knorr pyrrole synthesis. A simple mechanistic model for the PBG pyrrole synthesis reaction steps of the C-N and C-C bond formations is also investigated. The preferred mechanism for the PBG pyrrole synthesis is suggested to proceed by the formation of the C-N bond first followed by the C-C bond of the pyrrole ring through a mechanism similar to the Knorr pyrrole synthesis. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 2007. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Chemistry, Physical. | en_US |
| dc.title | Density functional theory studies on the chemistry and properties of selected pyrrole molecules. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
