Hydrocarbon radicals and their oxidation products

This dissertation describes two different experimental approaches that were used to study hydrocarbon radicals and their oxidation products. Whether surface bound or in the gas phase, hydrocarbon chemistry will have an immediate effect upon the atmosphere and in combustion.; The first part of the dissertation concerns the trapping of hydrocarbon species in a cold Ar matrix. Two different hydrocarbons were studied: propargyl radical (HCCCH2) and methyl radical (CH3). Propargyl radical, one of the simpler conjugated hydrocarbons, is believed to be a direct precursor of aromatic species in flames. Beams of propargyl were produced through the thermal dissociation of appropriate precursors. IR and Linear dichroism spectra of photooriented samples were measured to determine the polarization of the vibrational modes. Our results confirm the delocalized nature of propargyl radical, which demonstrates a striking resemblance to allyl radical (CH2CHCH2).; The reaction of propargyl radical with O2 was also studied. High frequency C-H stretches indicate the propargyl peroxyl (HC≡H 2OO) conformer was synthesized. No peaks corresponding to the allenyl peroxyl radical (OOCH=C=CH2) were detected.; Methyl radicals were co-deposited with O3 to form the elusive methyltrioxyl radical (CH3OOO). Trioxyl radicals have been postulated to be important intermediates in the atmospheric reaction of alkoxy radicals with O2. The infrared spectrum of methyltrioxyl radical was observed and compared to ab initio electronic structure calculations. These results provide some insight into the chemistry of trioxyl radicals.; The second part of the dissertation concerns the fabrication of a new apparatus used to study the oxidation of surface bound radicals. A surface of hydrocarbons can be "activated" by focusing a beam of OH radicals onto a thin film of hydrocarbons. A corona discharge of H2O in Ar was paired with a hexapole filter to create a clean, intense source of OH radicals. Preliminary reflection adsorption IR spectra of surface bound hydrocarbons were observed.