Özet:
This dissertation, employs computational methods to investigate i) the photooxidative degradation mechanisms of thiophene in boron-containing oligothiophenes and ii) the ignition reactions of hypergolic propellants. In the first part of this study, reactions betweeen thiophene group of boron-containing oligothiophenes and reactive oxygen species are analyzed. Reactive oxygen species used in this work can be listed as hydroxyl radical, hydroperoxyl radical, singlet molecular oxygen (1O2) and triplet molecular oxygen (3O2). Transition state structure for each reaction has been located. Free energy profile for every reaction mechanism is analyzed. In the second part of this study, the ignition reactions of hypergolic propellants are assessed. The reactions between the fuels and nitric acid are modeled. The initial salt formation is very exothermic and it supplies the energy for the ignition reactions: Habstraction, β-scission and N-N2 bond fission reactions. Reactants and products of the salt formation reactions are investigated by using the solvation model implicitly at 298.15°C in nitric acid. The transition state structures of the remaining reactions are located in vacuum at 423K. Analysis of their reaction kinetics has shed light to the ignition delay time difference between different fuels.
