Alkyne Combustion: Experimental and Theoretical Studies of Formyl Radical Production

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Jean Standard

Mentor Department



The formyl radical, HCO, is an important intermediate species in hydrocarbon combustion as it is a precursor to the hydroxyl radical, OH, which reacts with other abundant atmospheric species to form aerosol particles and acid rain. Under high temperature conditions, such as those in combustion reaction systems, alkanes will dehydrogenate to their corresponding alkene and alkyne forms. Computational studies have shown that oxygen atoms, O(3P), will attack at the triple bond of alkynes, leading to a complex series of reaction pathways containing many intermediate and transition state species. Previous experiments by the Quandt research group at Illinois State University have demonstrated varying intensities of HCO formation for a series of alkynes. Computational methods have been utilized by the Standard research group of Illinois State University to map out the potential energy surfaces of these alkyne + O(3P) reactions. In this work, the reactions of O(3P) with propargyl alcohol and 3-butyn-1-ol are investigated both experimentally and computationally. On the experimental front, cavity ring-down laser absorption spectroscopy (CRDLAS) was employed to detect the absorption spectrum of HCO. In order to better understand the reaction mechanisms of HCO formation in these reactions, computational methods were employed to find optimized geometries, vibrational frequencies, and potential energies of reactant, intermediate, transition state, and product structures at the M06-2x/cc-pVTZ and MP2/6-311++G(d,p) levels of theory. In addition, single-point energy calculations were carried out on the optimized molecular structures at the CCSD(T)/cc-pVTZ level of theory to construct potential energy profiles with more accurate energies. The aim of this study is to provide insight via theoretical methods that will help form a hypothesis for the variations of HCO signal intensity observed during the CRDLAS studies.



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