title: Photochemistry of UV-excited trifluoroacetylacetone and hexafluoroacetylacetone I: infrared spectra of fluorinated methylfuranones formed by HF photoelimination.
abstract: The photochemistry of gas-phase 1,1,1-trifluoroacetylacetone (TFAA) excited with ultraviolet (UV) light involves a significant photoelimination channel that produces hydrogen fluoride and a fluorinated methylfuranone, 2,2-difluoro-5-methyl-3(2H)-furanone (2FMF). This pathway is remarkable because it is a gas-phase unimolecular reaction that forms a five-membered ring product. This report is the first of such a TFAA photoelimination channel, which is similar to one observed with 1,1,1,5,5,5-hexafluoroacetylacetone (HFAA), resulting in 2,2-difluoro-5-trifluoromethyl-3(2H)-furanone. We present infrared spectral observations of 2FMF produced by pulsed, UV-laser excitation of TFAA, along with analogous results from HFAA, supported by density functional theory (DFT) computational studies. DFT results for the infrared spectrum of 5-methyl-3(2H)-furanone, the expected comparable acetylacetone photoelimination product, help suggest that UV excitation of acetylacetone fails to follow a similar type of photoelimination. We use a weighted RMS approach as a figure of merit for comparing calculated infrared frequencies with experimental data. Results from the three acetylacetones reveal how the presence of fluorine atoms in acetylacetone influences the gas-phase molecular photochemistry.
authors.affiliation: Department of Chemistry and Biochemistry, Calvin College, 1726 Knollcrest Circle SE, Grand Rapids, Michigan 49546, USA.
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Muyskens
authors.forename: Joel R
authors.initials: JR
authors.lastname: Alsum
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Thielke
authors.forename: Jodi L
authors.initials: JL
authors.lastname: Boer
authors.forename: Tina R
authors.initials: TR
authors.lastname: Heetderks
authors.forename: Mark A
authors.initials: MA
authors.lastname: Muyskens
mesh_terms: D005663:Furans / Q000737:chemistry*; D054879:Halogenation; D010422:Pentanones / Q000737:chemistry*; D055668:Photochemical Processes; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared; D014466:Ultraviolet Rays
chemical_list: D005663:Furans; D010422:Pentanones; C517499:hexafluoro-acetylacetone; C517498:1,1,1-trifluoro-2,4-pentanedione