On the atmospheric degradation of very short lived brominated compounds and their reservoir species

Monica Martinez-Aviles, Purdue University

Abstract

Under the international agreements for the protection of the ozone layer, the production of chlorofluorocarbons (CFCs), halons and several other halocarbons has been prohibited. Consequently, there is an interest in replacing these compounds. As part of the development of such replacing compounds, their potential effects on stratospheric ozone need to be evaluated. In the present work, the atmospheric oxidation mechanisms of bromoethane and bromopropane are thoroughly discussed with the use of ab initio molecular orbital methods aiming to identify other brominated species not yet accounted for. From these calculations, reaction enthalpies and activation energies are determined to characterize the potential energy surface of the proposed mechanisms for the complete atmospheric degradation of bromoethane and bromopropane. Moreover, modeling studies on the atmospheric degradation of bromopropane and its ODP are performed. Uncertainty in the ozone effects of bromoethane and bromopropane is associated to the lack of information regarding their respective brominated by-products for the atmospheric degradation chemistry. Ab initio molecular orbital methods have been used to determine the fundamental IR vibrational modes of HC(O)H, CH3C(O)H, BrC(O)H, BrCH2C(O)H, BrCH2CH 2C(O)H, CH3C(O)CH3, BrC(O)CH3, BrC(O)CH 2CH3, and BrCH2C(O)CH3. A complete assignment for all the fundamental modes has been made for all the species under study. The vibrational infrared spectra of the brominated reservoir species is theoretically modeled and compared to experimental values where available. Rotational constants are calculated and compared with the literature.

Degree

Ph.D.

Advisors

Francisco, Purdue University.

Subject Area

Analytical chemistry|Atmospheric sciences|Environmental science

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