Substituent effects on photodecarboxylation reactions of arylacetic acids
LE3 .A278 2015
Master of Science
This thesis is dedicated to studying excited-state EWGs that promote efficient PDC reactions of phenylacetic and mandelic acids. CF3-substituted compounds 46-53 have been previously investigated (Burns et al.7) and this thesis further investigates their photochemistry via UV-Vis and GC-MS studies. These studies suggest that the PDC reactions of these compounds are clean, and that they likely arise from a singlet excited state, although a small amount of PDC (<5%) did result in the formation of dimers. The ability of MeSO2, SO3 -, CN, Br and Cl substituents to promote PDC of phenylacetic acids was also investigated. p-MeSO2, p-SO3 -, p-CN and m-CN substituted phenylacetic acids underwent PDC very efficiently with quantum yields of PDC Φ = 0.38, 0.22, 0.55, and 1.00, respectively. UV-Vis studies were also employed on these compounds, and triplet state quenching and sensitization studies suggest that PDC occurs from either a singlet or short-lived triplet excited state. We also made progress towards the synthesis of CF3 and NO2 substituted diaryl phenylacetic acids. Additionally, a total of four coumarinylacetic acid derivatives were successfully synthesized and characterized, along with their corresponding expected photoproducts of PDC. The PDC reactions of coumarinylacetic acids 99-102 proved to be very efficient with quantum yields of PDC Φ = 0.50, 0.60, 0.60, and 0.83, respectively. The fluorescence quantum yields were also determined for coumarin derivatives 100 (Φ = 0.0034), 101 (Φ = 0.0035), 102 (Φ = 0.0027), 104 (Φ = 0.0036), 105 (Φ =0.0242), and 107 (0.0690). Triplet state quenching studies suggest these PDC reactions occur from both singlet and triplet excited states, with about 80% of PDC arising from the former.
The author grants permission to the University Librarian at Acadia University to reproduce, loan or distribute copies of my thesis in microform, paper or electronic formats on a non-profit basis. The author retains the copyright of the thesis.