ИСТИНА

Data obtained by Global Ozone Monitoring Experiment (GOME [1]) let us suggest that not only UV radiation lead to ozone depletion but it is also destructed during polar nights in heterogeneous processes involving polar stratospheric clouds (PSC) [2]. The Montreal protocol signing off provided the decrease of ozone depletion rate that was proved by monitoring. Mathematical models predict the restauration of ozone concentration in stratosphere by the end of 21st century [3]. Still, the observed ozone concentration is always less than calculated one hence the heterogeneous processes are difficult to take into account [4, 5]. In the unique laboratory unit that provides stratospheric conditions (pressure of 1-2 torr, temperature 77-250 K) we perform the interaction of ozone with possible halogen-substituted atmospheric pollutants (CCl3H, CBr3H, C2H5Cl, C2H5Br, C3H7Cl, C3H7Br, CCl3COOH, CCl2HCOOH, CClH2COOH, CBrH2COOH, C6H5Cl, C6H5Br, 1,2-C6H4Cl2, 1,3,5-C6H3Cl3) condensed on golden or ice surface. The IR-Fourier spectrometer allows to study the process in situ. The interaction between ozone and studied species started at 80-200 K temperature range depending on their individual properties. Equilibrium geometries and vibrational spectra of possible products (various chlorine and bromine oxides) are calculated by means of quantum-chemical calculations. B3LYP 6-311 G** level was chosen for all calculations. The formation of chlorine and bromine oxides is confirmed by low-temperature IR-spectroscopy. The presence of ice film lead to the hydrate formation that is decomposed only at temperature higher than 200 K. Three different mechanisms of ozone interference with halogen-substituted atmospheric pollutants according to their nature (saturated substance, aromatic substance or halogen-substituted acid), atomic charges and carbon-halogen bond energy. Bond energy between carbon and chlorine is higher than between carbon and bromine (for example in C2H5-Cl BDE is 352 kJ/mol compared to 293 kJ/mol for C2H5-Br and so on [6]) therefore all reactions with halogen atom detachment are more rapid in case of bromine than in case of chlorine. Alkanes interaction starts from the attack of ozone to the carbon atom, connected to the halogen atom, formation of intermediate