Theoretical investigations of photolysis for Halon-2402 in stratospheric layer

Abstract

Photolysis of Halon-2402(1,2-dibromotetrafluoroethane) in stratospheric layer have been investigated theoretically using quantum calculation methods likes DFT, ab-initio and semi-empirical. These methods have been carried out to estimate the depletion of ozone layer. Quantum calculations have been carried out for all suggested chemical moieties that’s participated in the photochemical reactions through optimizing geometry by PM3-configuration interaction microstate, HF, MP2 and DFT according to different basis sets. Calculations shows the photolysis reaction of Halon-2402 occurs through C-Br bond needed energy light equal to 92.3 kcal/mol (309.95 nm) in highly probability than other bonds. The recombination of photolysis radical products (•C2F4Br and Br•) is take out either Cis-addition of the Br radical into radical center to produce the gauche-conformer of TFEDB. The Trans-addition produces the anti-conformer of TFEDB. Clearly •C2F4Br radical has a classical nonbridged structure and the secondary dissociation is more possible than Cis or Trans-addition. The yield of atmospheric fate for TFEDB two radical of bromine and two FCOF fragments by oxidation process with O2. Two bromine radicals are responsible for the ozone depletion by direct pathway or indirect pathway through sharing with atmospheric chlorine radicals.