The vibrational spectra and normal coordinates analysis of bromofluoromethane, CH2BrF
The infrared gas-phase spectra of bromofluoromethane (CH2BrF) have been studied in the region below 6200 cm-1 under conditions of medium resolution. All the fundamentals and many overtones, combination and hot bands have been assigned leading to an almost complete set of anharmonicity constants. Rotational analyses have been performed on the observed Q-branch features of over 10 bands. Enriched 79Br and 81Br samples were also employed to confirm vibrational assignment and supply further data. Analyses of Fermi resonance are made. The molecular structure was calculated ab initio at the Hartree-Fock (HF), the second-order Moller-Plesset (MP2) and the density functional theory (DFT) level with the 6M311++G(3df, 2pd) basis set. The ab initio force constants obtained from the vibrational analysis at B3LYP/6-311++G(3df, 2pd) level of theory were employed to fit the experimental data and an optimal harmonic force field was obtained for the CH2BrF molecule. (C) 2000 Elsevier Science B.V.
Crystal Structure and Spectroscopic Investigation of Bromofluoro- and Fluoroiodomethane
The solid states of bromofluoromethane (BFM) and fluoroiodomethane (FIM) are characterized by X-ray diffraction analysis and by Raman spectroscopy. The single crystals were obtained by crystallization in situ at low temperature. BFM and FIM crystallize in the space group I2/a and Abm2, respectively. The Raman spectra of both compounds were recorded in different aggregation states and at different temperatures. Quantum chemical calculations and the X-ray diffraction data are considered to describe the noncovalent interactions of both compounds in the solid state. These interactions are discussed in the context of the σ-hole concept.
Feller, Michael,Lux, Karin,Kornath, Andreas
p. 5357 - 5362
(2016/01/25)
Catalytic reaction of methane with CBrF3
The catalytic reaction of CH4 with CBrF3 over Co, Cu and Mn ZSM-5 zeolites is described; major products (at low temperatures) are those expected for simple hydrodebromination: CH3Br and CHF3.
Li, Kai,Kennedy, Eric,Dlugogorski, Bogdan,Howe, Russell
p. 709 - 710
(2007/10/03)
Thermal Gas Phase Hydrodehalogenation of Bromochlorodifluoromethane
The thermal hydrodehalogenation of bromochlorodifluoromethane (Halon-1211; CBrClF2) in the gas phase has been studied using a plug flow alumina reactor at atmospheric pressure over the temperature range 400-900 degC with residence times of 2-3 s and CBrClF2/hydrogen molar intake ratios of ca. 10.Conversion of CBrClF2 starts at ca. 400 degC with C-Br bond homolysis followed by reaction with HX (X being Br, Cl or H) to yield CHClF2.At higher temperatures other products arise and complete conversion of CBrClF2 is achieved at ca. 600 degC.At temperatures above 850 degC complete dehalogenation to mainly methane (yield 80percent) is attained.In the temperature range 450-550 degC the (pseudo) first-order rate constant for the overall reaction (F) was found to obey: log (kF/s-1) = (9.4 +/- 1.5) - (150 +/- 25) kJ mol-1/2.303RT.The thermolysis of CBrClF2 was also studied using an excess of 2-phenylpropane (cumene) as a radical scavenger, resulting in the following Arrhenius expression for reaction (G): log (kG/s-1) = (15.1 +/- 0.5) - (262 +/- 9) kJ mol-1/2.303RT.From these parameters the bond dissociation energy for the C-Br bond in CBrClF2 was calculated to be 268 +/- 8 kJ mol-1, leading to a heat of formation of the CClF2-radical of -279 +/- 17 kJ mol-1.Kinetic analysis and separate experiments with H2O2 as an initiator for making H-radical showed that attack by H-radical is the main route for decomposition of CBrClF2.At temperatures higher than 500 degC HBr rather than H2 acts as a hydrogen transfer agent resulting in a fast radical chain (reactions G and L-O) with the observed Arrhenius parameters as a consequence.
Lijser, Huub J. P. de,Louw, Robert,Mulder, Peter
p. 139 - 146
(2007/10/02)
Process for the preparation of bromofluoromethane
A method for the preparation of bromofluoromethane by reducing dibromofluoromethane in the presence of mercury.