| dc.contributor.author | MacLeod, Paula Jane. | en_US |
| dc.date.accessioned | 2014-10-21T12:37:14Z | |
| dc.date.available | 1995 | |
| dc.date.issued | 1995 | en_US |
| dc.identifier.other | AAINN08784 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55091 | |
| dc.description | Photolysis of a benzylic compound with a leaving group can give products from radical intermediates, ionic intermediates or both. The factors that control the partitioning between these intermediates are not well understood. In fact, different mechanisms have been proposed for the formation of these two intermediates. If the mechanism and factors controlling the reactivity of benzylic substrates were known, then signed to give specific products. One application is in protecting group chemistry, a functional group could be protected with a benzylic substrate that has been designed to give products exclusively from either ionic or radical intermediates. | en_US |
| dc.description | Benzylic esters were chosen for study because upon photolysis they give mixtures of products. Esters 1-6 were studied to determine the effect of the following structural variations on product distribution: substituents on the aromatic ring, the R group, and conformational mobility. | en_US |
| dc.description | The proposed mechanism is homolytic cleavage from the singlet excited state to give a radical pair, a benzylic radical and an acyloxy radical. The radical pair then partitions between two pathways: decarboxylation of the acyloxy radical followed by coupling or electron transfer between the radical pair to give the ion pair. Heterolytic cleavage to give ion pairs directly is, at most, a minor pathway. Substituents changed product ratios by changing the oxidation potential of the benzylic radical and thus the rate of electron transfer. The R group changed the rate of decarboxylation. | en_US |
| dc.description | The major effect of substituents on the photochemistry of the conformationally restricted esters, 3-6, was also changing the oxidation potential of the benzylic radical. However, quantum yield studies showed that the substituents also have an electronic effect and can increase or decrease the efficiency of homolytic cleavage. Comparison of the results of esters 1 and 2 with those for 3-6 revealed a third effect of substituents. In a benzylic ester, where the bond that is cleaving is conformationally mobile, substituents can also alter the population of ground-state conformers and change quantum yields of reaction. | en_US |
| dc.description | The photochemistry of 1-naphthylmethyl phenyl and benzyl carbonates and carbamates was also studied. Again, the mechanism was homolytic cleavage to a give radical pair. The important competing pathways were decarboxylation and electron transfer.* ftn*Please refer to the dissertation for diagrams. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 1995. | 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, Physical. | en_US |
| dc.title | Mechanistic studies of the photolysis of substituted benzyl acetates and pivalates and 1-naphthylmethyl carbonates and carbamates. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
