Photochemical electrocyclic reactions have a long history of capturing the curiosity of scientists across disciplines. Especially the mechanisms leading to their high stereospecificity and the incredible success of the Woodward-Hoffmann rules in predicting the stereochemical outcome are of interest. This dissertation provides a detailed investigation of reaction path of photoinduced electrocyclic ring-opening by probing the dynamics of 1,3-cyclohexadiene (CHD) and α-terpenine (α-TP) upon photo excitation. Photoinduced ring-opening reactions play important roles in natural processes such as epidermal vitamin D synthesis, have practical applications as molecular switches, and are candidates for coherent control. We use time-resolved photoelectron spectroscopy to elucidate many intricate details of the reaction dynamics that relate to these applications. Specifically, time-resolved studies provide time scales for the individual stages of the interconversion reactions of CHD and α-TP to their respective reaction products, deepening our understanding of the reaction path. The dependence of the ring-opening dynamics on the energy initially deposited into the first excited state (1B), the understanding of which is crucial to the development of effective coherent control methods, are elucidated. Furthermore, examination of the dynamics following excitation into the lowest-lying Rydberg state (3p) revealed new insight about the nature of the transitions between the electronic surfaces. Finally, in view of the potential use of electrocyclic ring-opening reactions in molecular devices, the inertial effects of altering molecular structure were explored by comparing the dynamics of CHD to that of its substituted derivative, α-TP. We found that substitution of the ring by a methyl and a propyl group is able to slow down the electrocyclic reaction by a factor of two.
Pemberton, Christine C.,
"Reaction Paths of Photoinduced Electrocyclic Ring-Opening: 1,3-Cyclohexadiene and α-Terpinene"
Chemistry Theses and Dissertations.
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