Photochemistry of Fundamental Nitrogen Containing Aromatic Heterocycles

This thesis describes studies into gas-phase photochemistry of nitrogen containing heterocycles, together ion-trap mass spectrometers and tunable nanosecond laser light sources. The first part of the thesis focuses on the oxidation reaction of the 5-dehydrouracil radical cation. This radical cation is synthesised within the ion trap of a commercially available ion-trap mass spectrometer by irradiation of 5-iodouracil with 266nm photons. The reaction of the radical cation species with oxygen is observed across 5 and 3000 ms, and second order rate constants are measured to be 7.3±0.2⇥10−11 cm3 molecule-1 s-1 for this gas-phase oxidation reaction. Computational studies of the reaction pathways are undertaken using G4-MP2-6x and products assigned as 4,5-dioxo-4,5-dihydropyrimidin- 1-ium formation as well as decarbonylation of the quinone species.