Computational and Experimental Investigation of the Thermochemistry and Reaction Mechanisms of Atmospheric Degradation of Selected Nigerian Industrial Solvent Emissions

Volatile organic compounds emitted from industrial solvent use in Nigerian manufacturing facilities undergo complex atmospheric transformation chemistry that generates secondary pollutants including tropospheric ozone and secondary organic aerosol, yet the thermochemistry and mechanisms of these reactions under tropical West African atmospheric conditions are not documented. This dissertation presents an original computational and experimental investigation of the gas-phase atmospheric degradation mechanisms and thermochemistry of five industrially emitted solvents, including toluene, xylene, ethyl acetate, methyl ethyl ketone, and n-butanol, at atmospheric conditions representative of Nigerian industrial zones. Computational investigation was conducted using high-level quantum chemical methods at the CCSD(T)/aug-cc-pVTZ level, with thermochemical parameters derived from isodesmic reaction calculations. Rate constants for hydroxyl radical and nitrate radical reactions were calculated using canonical variational transition state theory with tunnelling corrections. Potential energy surfaces were mapped for key intermediate species. Experimental validation of selected reaction rate constants was performed using a smog chamber facility at ambient pressure and temperatures of 25 to 45 degrees Celsius, with mechanistic product identification by proton-transfer reaction mass spectrometry and FTIR spectroscopy. Ozone formation potentials and secondary organic aerosol yield coefficients were measured in smog chamber experiments and incorporated into a box model framework. Results reveal that toluene and xylene under Nigerian temperature and humidity conditions show substantially elevated ring-opening rates compared to temperate climate predictions. The dissertation contributes original thermochemical data, mechanism refinements, and secondary pollution prediction tools for Nigerian atmospheric chemistry. Keywords: atmospheric chemistry, solvent degradation, reaction mechanisms, computational chemistry, tropospheric ozone