| dc.contributor.author | Mangion, Bernardino. | en_US |
| dc.date.accessioned | 2014-10-21T12:36:18Z | |
| dc.date.available | 2001 | |
| dc.date.issued | 2001 | en_US |
| dc.identifier.other | AAINQ66652 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55781 | |
| dc.description | In the first part of this study, the electron transfer photochemistry between cyanoarene electron acceptors and aliphatic allene electron donors in the presence of methanol was investigated. In the reaction involving mononuclear arenes, such as 1,2,4,5-tetracyano- and 1,4-dicyanobenzene, a photochemical nucleophile-olefin combination, aromatic substitution (photo-NOCAS) reaction was observed. The strict regiochemistry in the isolated 1:1:1 arene-allene-methanol products, with the nucleophile attached exclusively to the central allenic carbon, confirmed the sequence of the mechanistic steps. In the case of 1,4-dicyanonaphthalene, the reaction started off along a pathway similar to the photo-NOCAS mechanism. However, the reaction eventually led to addition, rather than substitution, of the intermediate beta-methoxyallyl radical to the cyanoarene radical anion. The resulting adduct underwent further photochemical reactions involving either an intramolecular [2pi+2pi] cycloaddition or a nucleophile addition-cyclization. | en_US |
| dc.description | The intention of the second study was to develop a photochemical mechanism complementary in its regiochemical selectivity to the photo-NOCAS reaction, by inverting the sequence of mechanistic steps. For this purpose, the electron transfer photochemistry between a series of halobenzonitriles and 1,1-diphenylethene in methanol was investigated. Halobenzonitriles generate highly unstable radical anions that undergo rapid cleavage to give cyanophenyl radicals. The olefin radical cation should thus be trapped by this reactive intermediate prior to nucleophilic attack by methanol. Although the presence of a photoinduced electron transfer pathway was confirmed, the possibility of direct homolysis of the haloarene excited state, which would also generate an aryl radical, could not be discounted. The latter mechanism found support from a series of reactions involving 4-haloanisoles that were not capable of acting as electron acceptors. The two pathways are discussed and evaluated. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 2001. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Chemistry, Organic. | en_US |
| dc.subject | Chemistry, Radiation. | en_US |
| dc.title | Extending and diverting the photochemical nucleophile-olefin combination, aromatic substitution (photo-NOCAS) reaction. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
