| dc.contributor.author | Gonzalez, Carlos Miguel. | en_US |
| dc.date.accessioned | 2014-10-21T12:37:23Z | |
| dc.date.available | 2006 | |
| dc.date.issued | 2006 | en_US |
| dc.identifier.other | AAINR19601 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/54840 | |
| dc.description | The rate constants of decay of the excited singlet states (kd) of the o-, m- and p-isomers of cyanotoluene 1, arylboranate ester 2, trifluoromethyltoluene 3 (photochemically reactive isomers) and methylanisole 4 (photochemically stable even at 50°C), were determined by the measurement of the lifetimes of S1 (taus) in acetonitrile (AN) over a range of temperatures. In addition, measurements of taus were carried out in 2,2,2-trifluorethanol (TFE) for the o-, m- and p-isomers of cyanotoluene and arylboranate ester over the same range of temperatures. By fitting the experimental values of kd vs. T to a non-linear expression (the Arrhenius plot method), that includes rate constants for reaction (kr), fluorescence (k f), and intersystem crossing (kisc), the values for the rate constants for all of the processes of S1 were obtained reliably. Measurements of taus in AN and TFE indicated that the values of kr for S1 are greater when the ionization power of the solvent increases. The influence of the solvent on kd suggests that the prefulvene intermediates are polar. The values of kisc and kf obtained are essentially the same in both solvents. The dependence of taus on temperature for the isomers of methylanisole suggests that an activated intersystem crossing process may also take place. | en_US |
| dc.description | Dialkylsubstituted cyanobenzenes 5 and 6, and their cyclic analogues (indans 7 and 8, and tetralins 9 and 10) were studied in order to understand the geometric changes required to form the prefulvene intermediates, as well as the influence of ortho-methyl substitution on the photochemistry of cyano-substituted benzene compounds. The reactivity of S1 decreased (absence of photoproducts) for both of the compounds containing the neighbouring ring and the cyano substituted benzene compounds with an ortho-methyl group. The values of kisc and kr for S1 were again determined by the Arrhenius plot method. | en_US |
| dc.description | The photochemical addition of TFE to methoxy-substituted tolans 11 - 14 was also investigated. Solvent studies, including isotopic substitution experiments, were carried out to elucidate the reaction mechanism. The mechanism is consistent with a rate-determining proton transfer process, followed by a trapping of the resulting carbocation by the solvent. Compared to the parent tolan, m-methoxy and 3,4-dimethoxytolan display a larger quantum yield for fluorescence, as well as an increased photochemical reactivity toward the addition of TFE. The p-methoxy compound was also found to be more reactive photochemically toward TFE than tolan. | 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 | Temperature and solvent effects, rate constants and activation parameters for the reactions of the excited states of substituted benzene compounds. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
