| dc.contributor.author | Rodriguez-Evora, Yan. | en_US |
| dc.date.accessioned | 2014-10-21T12:36:31Z | |
| dc.date.available | 2006 | |
| dc.date.issued | 2006 | en_US |
| dc.identifier.other | AAINR16717 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/54808 | |
| dc.description | Naturally occurring compounds containing a 4-vinylphenol fragment are important components in several biological systems. Specifically, these classes of organic molecules are building blocks for the biosynthesis of natural products such as lignin, the second most abundant biopolymer on earth, and plant lignans, which frequently possess important therapeutic properties. 4-Vinylphenol radical cations are supposed to be involved in the biosynthesis of lignin and lignans, however practically nothing is known about these reactive species. | en_US |
| dc.description | This thesis therefore focuses on the generation and characterization of 4vinylphenol radical cations. Special attention is devoted to explore the viability of radical cation mediated dimerization of 4-vinylphenol substrates. The radical cations of coniferyl alcohol, isoeugenol and 2-methoxy-4-vinylphenol were generated by direct laser flash photolysis or by photoinduced electron-transfer. The lifetime of the radical cations in acidic acetonitrile were found to increase due to a shift in the radical cation - vinylphenoxyl radical acid-base equilibrium to the side of the radical cation. Additionally the reaction of 2-methoxy-4-vinylphenol radical cation with its neutral precursor has been found to proceed with a second order rate constant of 8.6 x 108 M-1s -1, indicating a possible [2+1] cycloaddition reaction. The radical cation of 2-methoxy-4-vinylphenol also reacts with non-phenolic substituted styrenes with second-order rate constants in the order of ca. 108 M-1s-1. | en_US |
| dc.description | The thesis also focuses on the chemistry of enol radical cations in solution. These species have been widely studied in the gas phase, however the information concerning the chemistry of these reactive species in solution is limited to enol radical cations generated from stable enols. The thesis describes the generation of five short-lived 1,2-diaryl enol radical cations in acidic acetonitrile. The generation of these species was achieved by protonation of alpha-carbonyl radicals initially formed by laser irradiation of alpha-bromoketones. The acid dissociation constants as well as the deprotonation rate constants for these species are highly influenced by the nature of the substituents on the aromatic rings. Theoretical optimization of the structures of the radical cations shows that these species are twisted, which compromises the conjugation between the charge and the substituents. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 2006. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Chemistry, Organic. | en_US |
| dc.title | Generation and characterization of 4-vinylphenol and 1,2-diaryl enol radical cations in solution. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
