1718-18-9Relevant articles and documents
Atmospheric Chemistry of CF2BrH: Kinetics and Mechanism of Reaction with F and Cl Atoms and Fate of CF2BrO Radicals
Bilde, Merete,Sehested, Jens,Mogelberg, Trine E.,Wallington, Timothy J.,Nielsen, Ole J.
, p. 7050 - 7059 (1996)
A pulse radiolysis technique was used to investigate the kinetics and products of the reaction of CF2BrH with fluorine atoms at 296 K.This reaction forms an adduct which is in dynamic equilibrium with CF2BrH and fluorine atoms.The UV absorption spectrum of the adduct was measured relative to the UV spectrum of the CH3O2 radical over the range 230-380 nm.At 280 nm, an absorption cross section of (1.3 +/- 0.3)E-17 cm2 molecule-1 was determined.From the absorption at 280 nm the equilibrium constant K5 = /() was measured to be (1.59 +/- 0.13)E-17 cm3 molecule-1.In 1 atm of SF6, the forward rate constant k5 = (1.4 +/- 0.5)E-11 cm3 molecule-1 s-1 and the backward rate constant k-5 = (8.8 +/- 3.0)E5 s-1 were determined by monitoring the rate of formation and loss of the adduct.As part of the present work a relative rate technique was used to measure k(Cl + CF2BrH) = (5.8 +/- 1.0)E-15 cm3 molecule-1 s-1 at 296 K and 700 Torr of N2.The fate of the oxy radical, CF2BrO, in the atmosphere is bromine atom elimination and formation of COF2.
Kinetic and mechanistic studies for reactions of CF3CH2CHF2 (HFC-245fa) initiated by H-atom abstraction using atomic chlorine
Chen, Junyi,Young, Valerie,Niki, Hiromi,Magid, Hillel
, p. 2648 - 2653 (1997)
Kinetics and mechanisms of Cl atom initiated oxidation reactions of CF3CH2CHF2 (HFC-245fa) were investigated by long-path FTIR spectroscopic methods at 297 ± 2 K. The Cl atoms initiated the reaction mainly via H-atom abstraction from the terminal carbon (≥95%) to produce a CF3CH2CF2 radical. Subsequent reactions in 700 Torr of air produced CF3CHO and CF2O as the primary products. Secondary reactions of CF3CHO with Cl atoms led to the formation of CF3C(O)OH, CF3OH, CO2, and CF3OOOCF3 in the experimental system. However, under atmospheric conditions, CF3CHO would undergo a series of rapid oxidation and decomposition reactions ultimately leading to HF and CO2, and no long-lived organic decomposition products would be produced.
The Open-Chain Trioxide CF3OC(O)OOOC(O)OCF3
Von Ahsen, Stefan,Garcia, Placido,Willner, Helge,Paci, Maximiliano Burgos,Argueello, Gustavo A.
, p. 5135 - 5141 (2007/10/03)
The open-chain trioxide CF3OC(O)OOOC(O)OCF3 is synthesised by a photochemical reaction of CF3C(O)OC(O)CF 3, CO and O2 under a low-pressure mercury lamp at -40°C. The isolated trioxide is a colourless solid at -40°C and is characterised by IR, Raman, UV and NMR spectroscopy. The compound is thermally stable up to -30°C and decomposes with a half-life of 1 min at room temperature. Between -15 and +14°C the activation energy for the dissociation is 86.5 kJ mol-1 (20.7 kcal mol-1). Quantum chemical calculations have been performed to support the vibrational assignment and to discuss the existence of rotamers.
1,1,1,3,3,-pentafluorobutane (HFC-365mfc): Atmospheric degradation and contribution to radiative forcing
Barry, John,Locke, Garrett,Scollard, Donncha,Sidebottom, Howard,Treacy, Jack,Clerbaux, Cathy,Colin, Reginald,Franklin, James
, p. 607 - 617 (2007/10/03)
The rate constant for the reaction of the hydroxyl radical with 1,1,1,3,3-pentafluorobutane (HFC-365mfc) has been determined over the temperature range 278-323 K using a relative rate technique. The results provide a value of k(OH + CF3CH2CF2CH3) = 2.0 × 10-12 exp(- 1750 ± 400/T) cm3 molecule-1 s-1 based on k(OH + CH3CCl3) = 1.8 × 10-12 exp (- 1550 ± 150/T) cm3 molecule-1 s-1 for the rate constant of the reference reaction. Assuming the major atmospheric removal process is via reaction with OH in the troposphere, the rate constant data from this work gives an estimate of 10.8 years for the tropospheric lifetime of HFC-365mfc. The overall atmospheric lifetime obtained by taking into account a minor contribution from degradation in the stratosphere, is estimated to be 10.2 years. The rate constant for the reaction of Cl atoms with 1,1,1,3,3-pentafluorobutane was also determined at 298 ± 2 K using the relative rate method, k(Cl + CF3CH2CF2CH3) = (1.1 ± 0.3) × 10-15 cm3 molecule-1 s-1. The chlorine initiated photooxidation of CF3CH2CF2CH3 was investigated from 273-330 K and as a function of O2 pressure at 1 atmosphere total pressure using Fourier transform infrared spectroscopy. Under all conditions the major carbon-containing products were CF2O and CO2, with smaller amounts of CF3O3CF3. In order to ascertain the relative importance of hydrogen abstraction from the - CH2 - and - CH3 groups in CF3CH2CF2CH3, rate constants for the reaction of OH radicals and Cl atoms with the structurally similar compounds CF3CH2CCl2F and CF3CH2CF3 were also determined at 298 K k(OH + CF3CH2CCl2F) = (8 ± 3) × 10-16 cm3 molecule-1 s-1; k(OH + CF3CH2CF3) = (3.5 ± 1.5) × 10-16 cm3 molecule-1 s-1; k(Cl + CF3CH2CCl2F) = (3.5 ± 1.5) × 10-17 cm3 molecule-1 s-1; k(C; + CF3CH2F3) -17 cm3 molecule-1 s-1. The results indicate that the most probable site for H-atom abstraction from CF3CH2CF2CH3 is the methyl group and that the formation of carbonyl compounds containing more than a single carbon atom will be negligible under atmospheric conditions, carbonyl difluoride and carbon dioxide being the main degradation products. Finally, accurate infrared absorption cross-sections have been measured for CF3CH2CF2CH3, and jointly used with the calculated overall atmospheric lifetime of 10.2 years, in the NCAR chemical-radiative model, to determine the radiative forcing of climate by this CFC alternative. The steady-state Halocarbon Global Warming Potential, relative to CFC-11, is 0.17. The Global Warming Potentials relative to CO2 are found to be 2210, 790, and 250, for integration time-horizons of 20, 100, and 500 years, respectively.
