C24. Characterizing the Products from F + t-butanol with Photoionization Mass Spectrometry: Hydrogen Migrations, b Scissions, Enolization

The isomerization and decomposition of alkoxy and alkyl radicals are important reactions in atmospheric and combustion systems; data for the latter is more abundant than those for the former. In the present study, t-butoxy (tBO) and hydroxy t-butyl (HOtB) radicals were formed by the reaction of F atoms with t-butyl alcohol in a flow tube; the F atoms being produced in a microwave discharge. Ions of the products were formed selectively by photoionization (PI) and subsequently analyzed via mass spectrometery (MS). The identification of isomeric products is nearly impossible with MS; however, the two-dimensional PIMS methodology provides "fingerprint" information so that various isomers (radicals and molecules) can be identified. The experiments were performed using the National Synchrotron Light Source (U-11 beamline with high intensity and tunable light) at the Brookhaven National Laboratory. The isomeric tBO and HOtB radicals (characterized by ionization threshold) can interconvert via a 1,3 hydrogen shift or decompose by b C-C or C-O bond rupture. The decomposition of tBO via b C-C rupture to produce acetone, which is well documented, was readily observed. The decomposition of HOtB produces both isobutene via C-O rupture and enol-acetone by C-C rupture; both products were observed. The reaction mechanism, energetics and ionization energies will be discussed from studies for both the t-butanol-H₉ and t-butanol-D₉ isotopomers.