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Darstellung und Charakterisierung atmosphaerenrelevanter Fluorverbindungen

Ahsen, Stefan von LSF

The present study is a contribution to the synthesis and extensive characterization of fundamental C, F, O containing compounds, which play an important role in the chemistry of the atmosphere due to their appearance in degradation processes of CFCs and their substitutes. The formation of the peroxy radicals CF3OO, FC(O)OO, CF3OC(O)OO, CF3C(O)OO, and CH3C(O)OO is achieved by low pressure thermolysis of suitable precursors, highly diluted in argon or neon and subsequent quenching of the reaction mixture as a matrix. In addition, the radicals CF3OCO, SF5, and CF3OOO are formed in matrix. All investigated radicals are characterized as matrix isolated species by IR- and UV-spectroscopy. The properties of the studied fluorocarbon peroxy radicals are comprehensively discussed. The first preparation of pure trifluoromethyl nitrate, CF3ONO2, is reported via different synthetic routes. The compound is completely characterized (IR, Raman, UV, NMR, melting and boiling point, vapour pressure, gas electron diffraction), a nd its chemistry is evaluated. It is demonstrated, that trifluoromethyl nitrate acts neither for CF3O radicals, nor for nitrogen dioxide as a reservoir species. With the synthesis of bistrifluoromethyl trioxydicarbonate, CF3OC(O)OO-OC(O)OCF3, a novel open-chain trioxide is obtained, which is thermally stable below -20°C. CF3OC(O)OOOC(O)OCF3 is characterized by IR, Raman, UV, NMR spectroscopy and is used in the generation of the previously unknown peroxy radical CF3OC(O)OO. For all investigated species quantum chemical calculations are performed. The consistent use of the density functional method B3LYP with the basis set 6-311G(d,p) allows a comprehensive theoretical study. In addition, band assignments of the spectra of the characterized compounds were supported by these calculations.

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Ahsen, Stefan von: Darstellung und Charakterisierung atmosphaerenrelevanter Fluorverbindungen.

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