| Abstract |
In the present thesis, the kinetic parameters and the mechanism of the elementary reactions of chlorine atoms with a series of fluorinated alcohols was studied in the gas phase. The impetus for this work was given by the proposal of hydrofluoroalcohols as substitutes of chlorofluorocarbons (CFC's). Therefore, the atmospheric chemistry as well as the role of fluoroalcohols in the environment surrounding the living creatures on this planet necessitate a thorough and complete study of their behaviour. The absolute rate constants of the reactions were determined with the Very Low Pressure Reactor (VLPR), an effusive molecular-beam technique, using a continuous flow of reactants and products which are directly and continuously monitored with a quadrupole mass spectrometer. The temperature dependence of the reaction rates of the three fluoroalcohols, 2,2,2-trifluoroethanol (CF3CH2OH), 2,2-difluoroethanol (CHF2CH2OH), and 2-fluoroethanol (CH2FCH2OH) was determined by performing experiments at four different temperatures, 273, 303, 333 και 363 Κ. The corresponding Arrhenius expressions, including the standard deviation(2σ), are listed below (in cm3 molecule-1 s-1): The experimental results have shown that all three reactions occur by the metathesis of a hydrogen atom, leading to the formation of hydrogen chloride (HCl) and the singly dehydrogenated radical of the corresponding alcohol. In addition, the mechanism of the tropospheric degradation of fluoroalcohols was clarified by studying the reactions of the primary radical products with molecular oxygen. The analysis of the different reaction channels was attempted by using characteristic mass spectral peaks, specific to each possible reaction product. The reaction enthalpies for all possible pathways for the reactions of fluoroalcohols with chlorine atoms, as well as the bond strengths for all C-H and O-H bonds were also calculated at reliable levels of theory. The calculations were performed by using DFT and ab-initio electronic structure methods, using the Quantum Chemistry package Gaussian94, on a cluster of Pentium PC's, running RedHat Linux, V6.1.
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Κινητική μελέτη αντιδράσεων ατομικού χλωρίου με φθοροαλκοόλες
