Formation of β-Fluoroethyl Radical and Closed-Shell Products in Reactions of Photogenerated Fluorine Atoms with Ethene in Solid Argon

Abstract

Solid-state reactions of F atoms with ethene molecules were initiated by UV photolysis of dilute solutions of F 2 and C 2 H 4 in solid Ar. Products stabilized in the matrix were detected by infrared spectroscopy. Experiments were conducted at different temperatures in order to distinguish reactions in matrix-isolated F 2 -C 2 H 4 complexes (at 16 K) from reactions of diffusing thermal F atoms (at 26 K). Comparison with the kinetic EPR data (Benderskii, V. A. et al. MendeleeV Commun. 1995, 6, 245) permitted the identification of the infrared spectrum of the β-fluoroethyl radical, which is the main product of the F + C 2 H 4 reaction. Frequencies and absolute absorption intensities of the eight strongest infrared bands of β-C 2 H 4 F are reported. Photolysis of isolated F 2 -C 2 H 4 complexes forms the closed-shell products C 2 H 3 F-HF and trans-and gauche-1,2-C 2 H 4 F 2 with relative yields 0.6:0.2:0.2. Successive addition of two thermal F atoms to an isolated C 2 H 4 molecule forms only the two conformers of 1,2-C 2 H 4 F 2 . The difference between product branching ratios of the latter reaction and the direct photoinduced reaction of F 2 -C 2 H 4 complexes is qualitatively explained by the difference in size of the reaction cages and excess energies of the vibrationally excited intermediate (C 2 H 4 F 2 )*.

Infrared Spectroscopic Observation of the Stabilized Intermediate Complex FO3 Formed by Reaction of Mobile Fluorine Atoms with Ozone Molecules Trapped in an Argon Matrix

“…The fact that the spectrum contains three X1 bands (corresponding to three isotopic combination 16 To test the photostability of the FO-O 2 complex to visible light, a sample containing the reaction products was subjected to irradiation by 532 nm laser light. The resulting spectra are shown in Figure 7.…”

“…Using this approach, we have recently determined the spectral characteristics of reactive intermediates formed by reactions of F atoms with ethene, 16 methane, 17 hydrogen, 18 carbon monoxide, 19 oxygen, 19 and nitric oxide. 20 In the present study, we have detected by FTIR spectroscopy the stabilized complex FO-O 2 in dilute mixtures of F 2 and O 3 in solid argon using F 2 as a photolytic precursor of F atoms.…”

Modern applications of matrix isolation technique to investigation of radical species generated in atom–molecular chemical reactions

“…In contrast to the gas-phase reaction, the reaction of diffusing fluorine atoms in solid argon results in stabilised intermediate as the major product. 39,128,129 High resolution of the HFS in the EPR spectra of isolated radicals 2-C 2 H 4 F…”

“…Eight vibrational frequencies of this radical were first determined by IR spectroscopy. 129 New reactive intermediates generated in solid-phase reactions of mobile fluorine atoms are considered below.…”

Conformational Isomerization of 1,2-Difluoroethane in Solid Argon: Cage-Modified Reaction Barriers

“…These results strongly support the assignments of the DFE(1) and DFE(2) bands to singly and doubly subsititutional sites, which were previously based only on the experimentally observed blue shift of the DFE(1) bands. 25 Figure 5 shows that the total potential energy of the system as a function of the internal rotation coordinate for the doubly and singly substitutional sites. In the first set of calculations, the potential was determined by rotation of one CH 2 F group starting from the equilibrium configuration of the lattice around trans-DFE.…”