Background, aim, and scope
The adverse environmental impacts of chlorinated hydrocarbons on the Earth’s ozone layer have focused attention on the effort to replace these compounds by nonchlorinated substitutes with environmental acceptability. Hydrofluoroethers (HFEs) and fluorinated alcohols are currently being introduced in many applications for this purpose. Nevertheless, the presence of a great number of C–F bonds drives to atmospheric long-lived compounds with infrared absorption features. Thus, it is necessary to improve our knowledge about lifetimes and global warming potentials (GWP) for these compounds in order to get a complete evaluation of their environmental impact. Tropospheric degradation is expected to be initiated mainly by OH reactions in the gas phase. Nevertheless, Cl atoms reaction may also be important since rate constants are generally larger than those of OH. In the present work, we report the results obtained in the study of the reactions of Cl radicals with HFE-7000 (CF3CF2CF2OCH3) (1) and its isomer CF3CF2CF2CH2OH (2).
Materials and methods
Kinetic rate coefficients with Cl atoms have been measured using the discharge flow tube–mass spectrometric technique at 1 Torr of total pressure. The reactions of these chlorofluorocarbons (CFCs) substitutes have been studied under pseudo-first-order kinetic conditions in excess of the fluorinated compounds over Cl atoms. The temperature ranges were 266–333 and 298–353 K for reactions of HFE-7000 and CF3CF2CF2CH2OH, respectively.
The measured room temperature rate constants were k(Cl+CF3CF2CF2OCH3) = (1.24 ± 0.28) × 10−13 cm3 molecule−1 s−1and k(Cl+CF3CF2CF2CH2OH) = (8.35 ± 1.63) × 10−13 cm3 molecule−1 s−1 (errors are 2σ + 10% to cover systematic errors). The Arrhenius expression for reaction 1 was k 1(266–333 K) = (6.1 ± 3.8) × 10−13exp[−(445 ± 186)/T] cm3 molecule−1 s−1 and k 2(298–353 K) = (1.9 ± 0.7) × 10−12exp[−(244 ± 125)/T] cm3 molecule−1 s−1 (errors are 2σ). The reactions are reported to proceed through the abstraction of an H atom to form HCl and the corresponding halo-alkyl radical. At 298 K and 1 Torr, yields on HCl of 0.95 ± 0.38 and 0.97 ± 0.16 (errors are 2σ) were obtained for CF3CF2CF2OCH3 and CF3CF2CF2CH2OH, respectively.
The obtained kinetic rate constants are related to the previous data in the literature, showing a good agreement taking into account the error limits. Comparing the obtained results at room temperature, k 1 and k 2, HFE-7000 is significantly less reactive than its isomer C3F7CH2OH. A similar behavior has been reported for the reactions of other fluorinated alcohols and their isomeric fluorinated ethers with Cl atoms. Literature data, together with the results reported in this work, show that, for both fluorinated ethers and alcohols, the kinetic rate constant may be considered as not dependent on the number of –CF2– in the perfluorinated chain. This result may be useful since it is possible to obtain the required physicochemical properties for a given application by changing the number of –CF2– without changes in the atmospheric reactivity. Furthermore, lifetimes estimations for these CFCs substitutes are calculated and discussed. The average estimated Cl lifetimes are 256 and 38 years for HFE-7000 and C3H7CH2OH, respectively.
The studied CFCs’ substitutes are relatively short-lived and OH reaction constitutes their main reactive sink. The average contribution of Cl reactions to global lifetime is about 2% in both cases. Nevertheless, under local conditions as in the marine boundary layer, τ Cl values as low as 2.5 and 0.4 years for HFE-7000 and C3H7CH2OH, respectively, are expected, showing that the contribution of Cl to the atmospheric degradation of these CFCs substitutes under such conditions may constitute a relevant sink. In the case of CF3CF2CF2OCH3, significant activation energy has been measured, thus the use of kinetic rate coefficient only at room temperature would result in underestimations of lifetimes and GWPs.
Recommendations and perspectives
The results obtained in this work may be helpful within the database used in the modeling studies of coastal areas. The knowledge of the atmospheric behavior and the structure–reactivity relationship discussed in this work may also contribute to the development of new environmentally acceptable chemicals. New volatile materials susceptible of emission to the troposphere should be subject to the study of their reactions with OH and Cl in the range of temperature of the troposphere. The knowledge of the temperature dependence of the kinetic rate constants, as it is now reported for the case of reactions 1 and 2, will allow more accurate lifetimes and related magnitudes like GWPs. Nevertheless, a better knowledge of the vertical Cl tropospheric distribution is still required.
This is a preview of subscription content, log in to check access.
Buy single article
Instant access to the full article PDF.
Price includes VAT for USA
Subscribe to journal
Immediate online access to all issues from 2019. Subscription will auto renew annually.
This is the net price. Taxes to be calculated in checkout.
Aranda A, Díaz-de-Mera Y, Rodríguez D, Salgado S, Martínez E (2002) Kinetic and products of the BrO+CH3SH reaction: temperature and pressure dependence. Chem Phys Lett 357:471–476
Aranda A, Díaz-de-Mera Y, Rodríguez A, Rodríguez D, Martínez E (2003) A kinetic and mechanistic study of the reaction of Cl atoms with acrolein: temperature dependence for abstraction channel. J Phys Chem A 107:5717–5721
Aranda A, Díaz-de-Mera Y, Bravo I, Rodríguez D, Rodríguez A, Martínez, E (2006) Atmospheric HFEs degradation in the gas-phase: reactions of HFE-7100 and HFE-7200 with Cl atoms at low temperatures. Environ Sci Technol 40:5971–5976
Aranda A, Díaz-de-Mera Y, Bravo I, Morales L (2007) Cyclooctane tropospheric degradation initiated by reaction with Cl atoms. Environ Sci Pollut Res Int 14(3):176–181
Atkinson R, Cox RA, Crowley JN, Hampson Jr RF, Hynes RG, Jenkin ME, Kerr JA, Rossi MJ, Troe J (2006) Summary of evaluated kinetic and photochemical data for atmospheric chemistry. IUPAC Subcommittee on Gas Kinetic Data Evaluation for Atmospheric Chemistry. Available at http://www.iupackinetic.ch.cam.ac.uk/summary/IUPACsumm_web_latest.pdf
Bedjanian Y, Laverdet G, Le Bras G (1998) Low-pressure study of the reaction of Cl atoms with isoprene. J Phys Chem A 102:953–959
Christensen LK, Wallington TJ, Guschin A, Hurley MD (1999) Atmospheric degradation mechanism of CF3OCH3. J Phys Chem A 103:4202–4208
Gilliland ER, Sherwood TK (1934) Diffusion of vapors into air streams. Ind Eng Chem 26:516–523
Harnisch J, de Jager D, Gale J, Stobbe O (2002) Halogenated compounds and climate change: future emission levels and reductions costs. Environ Sci Pollut Res Int 9(6):369–374
Harnisch J, Höhne N (2002) Comparison of emissions estimates derived from atmospheric measurements with national estimates of HFCs, PFCs and SF6. Environ Sci Pollut Res Int 9(5):315–320
Hurley MD, Wallington TJ, Andersen MPS, Ellis DA, Martin JW, Mabury SA (2004) Atmospheric chemistry of fluorinated alcohols: reaction with Cl atoms and OH radicals an atmospheric lifetimes. J Phys Chem A 108:1973–1979
Kaufman F (1984) Kinetics of elementary radical reactions on the gas phase. J Phys Chem 88:4909–4917
Kelly T, Sidebottom H (2002) A kinetic and mechanistic study of the atmospheric oxidation of 3,3,3-triflouropropanol. Poster CMD-2. Presented at the Eurotrac 2 Symposium, Garmisch-Partenkirchen, March. Available at http://imk-aida.fzk.de/CMD/AR2001/GPP18_4.pdf
Kondratyev KY, Varotsos CA (1995a) Atmospheric greenhouse-effect in the context of global climate-change. Nuovo Cimento Soc Ital Fis C 18:123–151
Kondratyev KY, Varotsos CA (1995b) Atmospheric ozone variability in context of global change. Int J Remote Sens 16:1851–1881
Kurylo MJ, Orkin VL (2003) Determination of atmospheric lifetimes via the measurement of OH radical kinetics. Chem Rev 103:5049–5076
Martínez E, Aranda A, Díaz-de-Mera Y, Rodríguez D, López MR, Albaladejo J (2002) Atmopheric degradation in the gas-phase: Cl–DMSO reaction. Temperature dependence and products. Environ Sci Technol 36:1226–1230
Molina MJ, Rowland FS (1974) Stratospheric sink for chlorofluoromethanes: chlorine atomic-catalysed destruction of ozone. Nature 249:810–812
Ninomiya Y, Kawasaki M, Guschin A, Molina LT, Molina MJ, Wallington TJ (2000) Atmospheric chemistry of n-C3F7OCH3: reaction with OH radicals and Cl atoms and atmospheric fate of n-C3F7OCH2O(×) radicals. Environ Sci Technol 34:2973–2978
Nohara K, Toma M, Kutsuna S, Takeuchi K, Ibusuki T (2001) Cl atom-initiated oxidation of three homologous methyl perfloroalkyl ethers. Environ Sci Technol 35:114–120
Papadimitriou VC, Prosmitis AV, Lazarou YG, Papagiannakopoulos P (2003) Absolute reaction rates of chlorine atoms with CF3CH2OH, CHF2CH2OH, and CH2FCH2OH. J Phys Chem A 107:3733–3740
Park JY, Slagle IR, Gutman D (1983) Kinetics of the reaction of chlorine atoms with vinyl bromide and its use for measuring chlorine-atom concentrations. J Phys Chem 87:1812–1818
Rajakumar B, Burkholder JB, Portmann RW, Ravishankara AR (2005) Rate coefficients for the OH+CFH2CH2OH reaction between 238 and 355 K. Phys Chem Chem Phys 7:2498–2505
Sellevåg SR, Nielsen CJ, Søvde OA, Myhre G, Sundet JK, Stordal F, Isaksen ISA (2004) Atmospheric gas-phase degradation and global warming potentials of 2-floroethanol, 2,2-difluoroethanol, and 2,2,2-trifluoroethanol. Atmos Environ 38:6725–6735
Singh HB, Thakur AN, Chen YE, Kanakidou M (1996) Tetrachloroethylene as an indicator of low Cl atom concentration in the troposphere. Geophys Res Lett 23:1529–1532
Spicer CW, Chapman EG, Finlayson-Pitts BJ, Plastridge RA, Hubbe JM, Fast JD, Berkowitz CM (1998) Unexpectedly high concentrations of molecular chlorine in coastal air. Nature 394:353–356
Taatjes CA, Christensen LK, Hurley MD, Wallington TJ (1999) Absolute and site-specific abstraction rate coefficients for reactions of Cl with CH3CH2OH, CH3CD2OH, and CD3CH2OH between 295 and 600 K. J Phys Chem A 103:9805–9814
Tokuhashi K, Takahashi A, Kaise M, Kondo S, Sekiya A, Yamashita S, Ito H (1999) Rate constants for the reactions of OH radicals with CH3OCF2CF3, CH3OCF2CF2CF3, and CH3OCF(CF3)2. Int J Chem Kinet 31:846–853
We thank the Spanish Ministry of Science–Education and the Castilla-La Mancha Science–Education Council for their financial support. We thank Luis Tello (3M Corp.) for supplying samples of HFE-7000.
Responsible editor: Constantini Samara
About this article
Cite this article
Díaz-de-Mera, Y., Aranda, A., Bravo, I. et al. Atmospheric chemistry of HFE-7000 (CF3CF2CF2OCH3) and 2,2,3,3,4,4,4-heptafluoro-1-butanol (CF3CF2CF2CH2OH): kinetic rate coefficients and temperature dependence of reactions with chlorine atoms. Environ Sci Pollut Res 15, 584 (2008). https://doi.org/10.1007/s11356-008-0030-3
- CFCs substitutes
- Gas phase