Substituent effects on photodecarboxylation reactions of arylacetic acids
LE3 .A278 2015
2015
Lukeman, Matthew
Acadia University
Master of Science
Masters
Chemistry
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.
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https://scholar.acadiau.ca/islandora/object/theses:397