Matthew C. Drummer Robert W. Quandt Jean M. Standard Department of Chemistry Illinois State University Normal, IL 61790-4160 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 a series of alkynes is 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 for butyne, pentyne, and propargyl alcohol. 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, MP2/6-311++G(d,p), and B3LYP/cc-pvTZ 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.

Alkyne combustion: Experimental and theoretical studies of formyl radical formation

255th National Meeting (2018)

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