Mechanistic studies of the photolysis of substituted 1-naphthylmethyl esters and substituted benzyl acetates.
Date
1990
Authors
Hilborn, James Wallace.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
The photochemistry of four different ester series, was investigated in order to understand the mechanism of excited state cleavage reactions. Two of the ester series were substituted 1-naphthylmethyl alkanoates, 1a-h*, and phenylacetates, 2a-k, and the other two being substituted benzyl acetates, 3a-e, and 2,2-dimethylpropanoates, 4a-e.
Esters 1a-h, and 2a, 2d-k, were shown to behave similarly upon photolysis in methanol with constant fluorescence quantum yields $(\Phi\sb{\rm f})$ and singlet lifetimes $(\tau\sb{\rm s})$. From the product ratios in the photolysis, the rates of decarboxylation of the acyloxy and aryloxy radicals were obtained. The results were rationalized using radical stability arguments. Esters 2b and 2c were shown to behave unusually since their fluorescence quantum yield and singlet lifetime were decreased markedly compared to the other esters. These unusual effects were rationalized by assuming that charge transfer or exciplex formation had occurred in the excited state.
The photochemistry of the benzylic esters, 3a-e and 4a-e, was examined in order to compare substituent effects in excited state benzene chemistry with those previously determined for naphthalene cases. The special effect of the meta methoxy compound was investigated. The importance of the electron transfer process converting radical pairs to ion pairs in determining product ratios was assessed. ftn*Please refer to dissertation for diagrams.
Thesis (Ph.D.)--Dalhousie University (Canada), 1990.
Esters 1a-h, and 2a, 2d-k, were shown to behave similarly upon photolysis in methanol with constant fluorescence quantum yields $(\Phi\sb{\rm f})$ and singlet lifetimes $(\tau\sb{\rm s})$. From the product ratios in the photolysis, the rates of decarboxylation of the acyloxy and aryloxy radicals were obtained. The results were rationalized using radical stability arguments. Esters 2b and 2c were shown to behave unusually since their fluorescence quantum yield and singlet lifetime were decreased markedly compared to the other esters. These unusual effects were rationalized by assuming that charge transfer or exciplex formation had occurred in the excited state.
The photochemistry of the benzylic esters, 3a-e and 4a-e, was examined in order to compare substituent effects in excited state benzene chemistry with those previously determined for naphthalene cases. The special effect of the meta methoxy compound was investigated. The importance of the electron transfer process converting radical pairs to ion pairs in determining product ratios was assessed. ftn*Please refer to dissertation for diagrams.
Thesis (Ph.D.)--Dalhousie University (Canada), 1990.
Keywords
Chemistry, Organic., Chemistry, Physical.