Document e5a3Y4YRBvJv9mZeOdL5awdgy

ARTICLE pubs.acs.org/JPCA Atmospheric Chemistry of (Z)-CF3CHdCHCF3: OH Radical Reaction Rate Coefficient and Global Warming Potential Munkhbayar Baasandorj,, A.R. Ravishankara, and James B. Burkholder*, Earth System Research Laboratory, Chemical Sciences Division, National Oceanic and Atmospheric Administration, 325 Broadway, Boulder, Colorado 80305-3328, United States Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado 80309, United States bS Supporting Information ABSTRACT: Rate coefficients, k, for the gas-phase reaction of the OH radical with (Z)-CF3CHdCHCF3 (cis-1,1,1,4,4,4hexafluoro-2-butene) were measured under pseudo-first-order conditions in OH using pulsed laser photolysis (PLP) to produce OH and laser-induced fluorescence (LIF) to detect it. Rate coefficients were measured over a range of temperatures (212374 K) and bath gas pressures (20200 Torr; He, N2) and found to be independent of pressure over this range of conditions. The rate coefficient has a non-Arrhenius behavior that is well-described by the expression k1(T) = (5.73 ( 0.60) 1019 T2 exp[(678 ( 10)/T] cm3 molecule1 s1 where k1(296 K) was measured to be (4.91 ( 0.50) 1013 cm3 molecule1 s1 and the uncertainties are at the 2 level and include estimated systematic errors. Rate coefficients for the analogous OD radical reaction were determined over a range of temperatures (262374 K) at 100 Torr (He) to be k2(T) = (4.81 ( 0.20) 1019 T2 exp[(776 ( 15)/T], with k2(296 K) = (5.73 ( 0.50) 1013 cm3 molecule1 s1. OH radical rate coefficients were also measured at 296, 345, and 375 K using a relative rate technique and found to be in good agreement with the PLPLIF results. A room-temperature rate coefficient for the O3 + (Z)-CF3CHdCHCF3 reaction was measured using an absolute method with O3 in excess to be <6 1021 cm3 molecule1 s1. The atmospheric lifetime of (Z)-CF3CHdCHCF3 due to loss by OH reaction was estimated to be 20 days. Infrared absorption spectra of (Z)-CF3CHdCHCF3 measured in this work were used to determine a (Z)CF3CHdCHCF3 global warming potential (GWP) of 9 for the 100 year time horizon. A comparison of the OH reactivity of (Z)CF3CHdCHCF3 with other unsaturated fluorinated compounds is presented. 1. INTRODUCTION The Montreal Protocol (1987), and its subsequent adjust- ments and amendments, has led to the commercial replacement of ozone-depleting substances (ODS), including chlorofluorocarbons (CFCs) and bromofluorocarbons (halons), with hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) in many cases. CFCs now exhibit substantially reduced rates of atmospheric growth, and a decline in the atmospheric abundance of some compounds has been observed. The atmospheric abundances of HCFCs and HFCs, on the other hand, are generally increasing.1 HCFCs are considered to be transitional replacements and are scheduled for phase-down under the Montreal Protocol.1,2 HFCs are not ozone-depleting compounds but are potent greenhouse gases that are included under the Kyoto Protocol (1997).3 The radiative forcing due to HFCs is projected to increase as the use of HFCs increases, with a potentially significant contribution to climate forcing.4 It is, therefore, important that HFC replacement compounds and their atmospheric degradation products have acceptably low global warming potentials (GWPs) in addition to having a negligible impact on the environment, for example, low photochemical ozonecreation potentials (POCP). Unsaturated hydrofluorocarbons (HFOs, hydrofluoro-olefins) are currently being considered as viable replacement compounds due in part to their greater reactivity in the atmosphere with the OH radical than the HFCs that they replace, which results in shorter atmospheric lifetimes. A shorter atmospheric lifetime in most cases leads to a lower GWP for HFOs compared to that for the HFCs that they replace. (Z)-CF3CHdCHCF3 (cis-1,1,1,4,4, 4-hexafluoro-2-butene) is a potential replacement compound currently under consideration. Prior to its use in commercial applications and possible release into the atmosphere, its atmospheric chemistry and potential impact on the environment need to be understood. The primary atmospheric loss process for (Z)CF3CHdCHCF3 is expected to be reaction with the OH radical OH Z-CF3CHdCHCF3 f Products 1 Analogous to other alkene reactions, reaction 1 is expected to proceed via addition to the carboncarbon double bond, resulting in the formation of a stable HOHFC adduct radical. Received: Revised: Published: June 30, 2011 August 11, 2011 September 01, 2011 r 2011 American Chemical Society 10539 dx.doi.org/10.1021/jp206195g | J. Phys. Chem. A 2011, 115, 10539-10549 The Journal of Physical Chemistry A ARTICLE In the atmosphere, the HOHFC adduct would, most likely, react with O2, leading to the irreversible removal of (Z)CF3CHdCHCF3. In this study, rate coefficients for reaction 1, k1(T), were measured as a function of temperature (212374 K) and pressure (20200 Torr, He, N2) using a pulsed laser photolysislaser induced fluorescence (PLPLIF) technique and at 296, 345, and 375 K using a relative rate (RR) technique at pressures between 100 and 300 Torr (He). To our knowledge, rate coefficient studies for reaction 1 have not been reported in the literature to date. Rate coefficients for the OD reaction OD Z-CF3CHdCHCF3 f Products 2 were also measured as part of this study to gain additional insight into the mechanism of reaction 1. A comparison of the (Z)CF3CHdCHCF3 reactivity with that of other unsaturated fluorinated compounds is presented. The reaction of (Z)CF3CHdCHCF3 with O3 was briefly examined and shown to represent only a minor atmospheric loss process. The radiative efficiency and global warming potential of (Z)-CF3CHdCHCF3 were calculated using its infrared absorption spectrum measured as part of this work. 2. EXPERIMENTAL DETAILS The pulsed PLPLIF5,6 and RR7,8 apparatus have been used previously in our laboratory, and only details relevant to the present study are described separately below. Measurements of the O3 + (Z)-CF3CHdCHCF3 reaction rate coefficient at 296 K and the infrared absorption cross sections of (Z)-CF3CHd CHCF3 are described in sections 2.3 and 2.4, respectively. 2.1. Pulsed Laser PhotolysisLaser-Induced Fluorescence (PLPLIF). Reaction rate coefficients were measured under pseudo-first-order conditions in OH, [HFO] . [OH], with OH radicals produced via the 248 nm (KrF excimer laser) pulsed laser photolysis of H2O2 (hydrogen peroxide) or (CH3)3COOH (t-butyl hydroperoxide) H2O2 h f 2OH 3 CH33COOH h f product OH 4 where the OH quantum yield for reaction 3 is 29 and that for reaction 4 is unity.10 H2O2 photolysis was used for kinetic measurements at temperatures > 250 K. For temperatures < 250 K, (CH3)3COOH photolysis was used. Details of the (CH3)3COOH photolysis OH radical source are provided in a recent study from this laboratory.10 The initial OH radical concentration, [OH]0, was estimated from the precursor concentration, its absorption cross section at 248 nm, the precursor OH quantum yield, and the photolysis laser power, which was measured at the exit of the LIF reactor with a calibrated power meter. The photolysis laser fluence was varied between 3 and 17 mJ cm2 pulse1 over the course of the study. The concentrations of H2O2 and (CH3)3COOH in the LIF reactor were estimated from the pseudo-first-order rate coefficients measured in the absence of (Z)-CF3CHdCHCF3. The temperature of the 150 cm3 Pyrex LIF reactor was controlled by circulating fluid from a temperature-regulated reservoir through its jacket. The temperature of the gas in the reactor was measured with a retractable thermocouple and was accurate to within (1 K. OD radicals were produced using 248 nm pulsed laser photolysis of O3 in a He bath gas to produce O(1D) followed by its reaction with D2O O1D D2O f 2OD 5 The D2O concentration was estimated from gas flow rates and pressures to be 3 1016 molecules cm3, which is sufficient to remove 99% of the O(1D) within 1 s after the photolysis pulse and quench the vibrationally excited OD produced in reaction 5 within 15 s.11 The O3 concentration in the LIF reactor was estimated to be 4 1012 molecules cm3. OH radical fluorescence was detected following pulsed laser excitation in the A2+(v = 1) r X2(v = 0) transition near 282 nm using the frequency-doubled output from a Nd:YAG pumped dye laser. OD fluorescence was detected following excitation near 287.6 nm. The probe laser beam propagated through the LIF reactor at a right angle to the larger diameter photolysis laser beam. The photolysis and probe beams inter- sected in the middle of the reactor. Fluorescence from the reaction zone was detected by a photomultiplier tube (PMT) mounted orthogonal to the plane of the photolysis and probe laser beams. A band-pass filter (308 nm, fwhm =10 nm) mounted in front of the PMT was used to isolate the OH fluorescence. The PMT signal was averaged for 100 laser shots with a gated charge integrator. OH temporal profiles were measured by varying the delay between the photolysis and the probe lasers (i.e., the reaction time) between 10 s and 50 ms. OH temporal profiles followed the integrated first-order rate expression ! ln OHt ln St OH0 S0 k1Z-CF3CHdCHCF3 kdt k0t I where St is the measured OH signal at time t, which is proportional to [OH]t, [(Z)-CF3CHdCHCF3] is the (Z)-CF3CHd CHCF3 concentration in the LIF reactor, and k0 and kd are the first-order rate coefficients for loss of OH in the presence and absence of (Z)-CF3CHdCHCF3, respectively. The k0 values were obtained as the slope of a nonlinear least-squares fit of St versus time. kd represents the loss of OH due primarily to its reaction with the OH precursor and diffusion out of the detection volume. The actual values of kd depended on the OH radical precursor and its concentration but were in the range of 50 500 s1. OH temporal profiles were measured over a range of (Z)-CF3CHdCHCF3 concentrations at each temperature and pressure. Rate coefficients, k1(T), were determined as the slope of k0 versus [(Z)-CF3CHdCHCF3] using a linear least-squares fit of the data weighted by the measurement precision. 2.2. Relative Rate (RR) Measurements. In the RR method, the loss of the reactant compound, (Z)-CF3CHdCHCF3, was measured relative to the loss of a reference compound that has a well-established reaction rate coefficient. Provided the reactant and reference compounds are lost via the same reaction, in this case, reaction with the OH radical, the rate coefficients for the two reactions are related by ! ! ln Z-CF3CHdCHCF30 kZ ln Ref 0 II Z-CF3CHdCHCF3t kRef Ref t 10540 dx.doi.org/10.1021/jp206195g |J. Phys. Chem. A 2011, 115, 10539-10549 The Journal of Physical Chemistry A where the 0 and t subscripts indicate the initial concentrations at time zero and concentrations during the reaction at time t. The kZ and kRef are the rate coefficients for the (Z)-CF3CHd CHCF3 and reference reaction with OH. C2H6 was used as the reference compound, where k(T) = 7.66 1012 exp[1020/T] cm3 molecule1 s1 and k(296 K) = (2.50 ( 0.23) 1013 cm3 molecule1 s1 for the OH + C2H6 reaction.9 Several experiments were performed using CH3CH2Cl as a reference compound. However, the use of CH3CH2Cl led to systematic deviations due to secondary loss of (Z)-CF3CHdCHCF3, which was most noticeable at reactant losses > 20%. HCl formation was observed during the experiment, suggesting a possible interference from Cl atom reactions. A rate coefficient obtained using data obtained with small reactant conversion was, however, found to be in agreement with the results obtained using C2H6 as the reference compound. The results obtained in the CH3CH2Cl experiments were not used in the final kinetic analysis due to the possible contributions of systematic errors in the measurements. The apparatus used for the RR measurements has been described in detail elsewhere.7,8 The apparatus consisted of a 100 cm long reaction cell (5 cm i.d.) coupled to a Fourier trans form infrared spectrometer (FTIR) for measuring the reactant concentrations. OH radicals were produced using the 248 nm pulsed laser photolysis of O3 in a He bath gas to produce O(1D) followed by its reaction with H2O O1D H2O f 2OH 6 Experiments were performed by first filling the reactor with (Z)CF3CHdCHCF3, reference compound, H2O vapor, and 100 Torr He bath gas. The gases were thoroughly mixed using a Teflon diaphragm circulation pump. The (Z)-CF3CHdCHCF3 and reference compound concentrations were then measured by infrared absorption. Ozone was then slowly added to the circulating gas mixture by passing a small flow of He through the O3 reservoir while the photolysis laser beam was passed along the length of the reactor. The residence time of the gas in the reaction cell was 6 s. The steady-state O3 concentration was estimated to be 1 1014 molecules cm3. The H2O vapor concentration was estimated to be 4 1017 molecules cm3, which was sufficient to scavenge >99% of the O(1D) atoms, that is, the loss of (Z)-CF3CHdCHCF3 or C2H6 due to reaction with O(1D) was estimated to be <0.3 or <1% (worst case), respectively, of their measured loss. The total pressure of the system increased due to the addition of O3/He during the experiment from 100 to 200 Torr over the duration of an experiment. The reactant and reference compound loss was measured by infrared absorption. Infrared spectra were recorded at a spectral resolution of 1 cm1 between 500 and 4000 cm1 with 20 coadded interferograms. The losses of C2H6 and (Z)-CF3CHd CHCF3 were monitored using the absorption bands near 820 and 3000 cm1 and bands between 1000 and 1500 cm1, respectively. In dark experiments, performed under identical conditions but without the photolysis laser beam, there was no observable change, <0.5%, in the reactant concentrations over a period of 2 h with a pressure increase from 100 to 500 Torr (He). The photolysis laser fluence was measured at the exit of the reactor with a power meter and was constant to within 5% during an experiment but was varied over the range of 1226 mJ cm2 pulse1 over the course of the study. The initial concentrations were varied in the individual experiments with values in the range of (613) 1014 molecules cm3 for (Z)-CF3CHdCHCF3 ARTICLE and (0.510) 1015 molecules cm3 for C2H6. Several experiments were also performed with O2, 7 1016 molecules cm3, added to the initial reaction mixture to test for possible contributions from secondary radical chemistry. 2.3. O3 + (Z)-CF3CHdCHCF3 Rate Coefficient. The roomtemperature rate coefficient for the reaction of O3 with (Z)CF3CHdCHCF3 was measured under static conditions at pressures between 100 and 250 Torr (He) using infrared absorption to monitor the loss of (Z)-CF3CHdCHCF3 in the presence of excess O3. Rate coefficients were measured under pseudo-firstorder conditions in (Z)-CF3CHdCHCF3, [O3] . [(Z)-CF3CHd CHCF3], and interpreted assuming that the observed (Z)CF3CHdCHCF3 loss was due solely to its reaction with O3. Experiments were performed using the same apparatus setup used in the OH RR measurements described above. Several experiments were performed using the multipass infrared absorption cell as the reactor, that is, without circulation of the gases. The O3 concentration was varied over the range of (1.98.6) 1016 molecules cm3 during the course of the study and was quantified using its infrared absorption band near 2100 cm1.12 The (Z)-CF3CHdCHCF3 concentration was in the range of (3.97.5) 1014 molecules cm3 with [O2] in the range of (0.510) 1016 molecules cm3. Rate coefficients were obtained from a linear least-squares fit of the measured pseudofirst-order rate coefficients versus [O3]. 2.4. UV and Infrared Absorption Measurements. UV (184.9 and 253.6 nm) and infrared absorption cross sections of (Z)-CF3CHdCHCF3 were determined in this work and used in monitoring its concentration online in the PLPLIF kinetic measurements, measuring the rate coefficient of the O3 + (Z)CF3CHdCHCF3 reaction, as well as in the determination of its GWPs. Absorption cross sections were determined at room temperature, 296 K, and were based on absolute pressure measurements made under static conditions with manometrically prepared mixtures of (Z)-CF3CHdCHCF3 (0.7 and 8% in He) as well as pure samples. UV absorption was measured using a Hg pen-ray lamp light source, a 100 cm long absorption cell, and a band-pass filter mounted in front of a photodiode detector (solar blind detector for 185 nm). Absorption cross sections were determined from measurements made over a range of (Z)-CF3CHdCHCF3 concentrations using Beer's Law I A ln I0 LZ-CF3CHdCHCF3 III where I and I0 are the transmitted intensity through the cell with and without (Z)-CF3CHdCHCF3 present, respectively, is the (Z)-CF3CHdCHCF3 absorption cross section, and L is the path length of the absorption cell. The range of (Z)-CF3CHdCHCF3 concentrations used was (0.783.70) 1016 molecules cm3 for 184.9 nm and (0.11) 1019 molecules cm3 for 253.6 nm. A linear least-squares analysis of A versus [(Z)-CF3CHd CHCF3] yielded a 184.9 nm absorption cross section of (4.97 ( 0.02) 1019 cm2 molecule1, where the quoted uncertainties are at the 2 level from the precision of the fit, eq III. Absorption cross sections obtained using different sample mixtures were identical within the precision of the measurement. For 253.6 nm, a cross section upper-limit of <4 1024 cm2 molecule1 was determined. In the kinetic experiments, UV absorption of (Z)CF3CHdCHCF3 at 184.9 nm was measured before the sample entered the LIF reactor. 10541 dx.doi.org/10.1021/jp206195g |J. Phys. Chem. A 2011, 115, 10539-10549 dx.doi.org/10.1021/jp206195g |J. Phys. Chem. A 2011, 115, 10539-10549 10542 Table 1. Summary of Experimental Conditions and Rate Coefficients Obtained For the OH + (Z)-CF3CHdCHCF3 Reaction T P [O2] v photolysis laser fluence [precursor] [OH]0 [Z-CF3CHdCHCF3] (K) (Torr) bath gas (1016 molecules cm3) (cm s1) (mJ cm2 pulse1) (1014 molecules cm3) (1011 molecules cm3) (1015 molecules cm3) 212 200 He 6.9 10.4 0.86a 0.22 0.8813.3 212 200 He 7.5 10.7 0.87a 0.23 0.5315.5 212 200 He 3.6 7.5 10.7 0.87a 0.23 0.5315.5 220 200 He 7.7 10.7 0.69a 0.18 0.5811.7 220 200 N2 6.6 11 0.71a 0.19 0.8015.8 220 200 N2 4.05 6.6 11 0.71a 0.19 0.9515.7 227 200 He 6.5 11.4 1.01a 0.29 0.9716.3 227 200 He 4.20 6.5 11.4 1.01a 0.29 0.6815.4 227 200 N2 6.8 10.4 1.02a 0.30 0.7514.9 239 100 He 239 200 He 9.6 9.4 1.73a 0.41 0.9114.4 6.6 15.9 1.04a 0.41 0.8814.5 253 200 He 253 100 N2 6.9 11.9 0.35b 0.94 1.1518.1 8.6 14.8 1.47b 4.86 0.8012.8 270 200 He 270 200 He 7.4 11.9 0.34b 0.92 0.8016.5 7.4 11.9 0.34b 0.92 0.4213.3 296 50 He 12.3 15.1 0.96b 3.26 0.3617.3 296 100 He 11.9 16.7 0.59b 2.21 0.536.5 296 100 He 15.7 7.0 0.97b 1.52 0.3913.0 296 100 He 1.2 11.8 9.4 1.64a 0.39 0.7215.3 296 200 He 7.8 17.4 0.22b 0.88 2.2324.5 296 200 He 7.8 15.8 0.43b 1.54 0.6517.2 296 200 He 3.39 7.8 15.8 0.43b 1.54 0.5719.1 296 100 N2 7.6 6.3 2.01b 2.87 0.5218.0 296 100 N2 3.64 7.6 6.3 2.01b 2.87 0.5118.4 319 200 He 338 200 He 338 200 N2 338 200 N2 7.9 8.6 0.53b 1.02 0.4016.2 8.1 8.6 0.66b 1.27 1.1816.0 8.0 14.7 0.55b 1.83 0.9721.2 8.0 14.7 0.55b 1.83 0.9218.5 357 200 He 374 24 He 8.6 8.6 0.67b 1.29 0.5113.7 14 14.3 0.40b 1.27 0.3311.4 kc (1013 cm3 molecule1 s1) 6.36 ( 0.10 6.21 ( 0.05 6.21 ( 0.08 k(212 K) = 6.26 ( 0.06d 6.23 ( 0.08 6.21 ( 0.10 6.21 ( 0.11 k(220 K) = 6.21 ( 0.06d 5.96 ( 0.08 5.97 ( 0.05 5.92 ( 0.08 k(227 K) = 5.96 ( 0.03d 5.63 ( 0.04 5.64 ( 0.06 k(239 K) = 5.63 ( 0.04d 5.29 ( 0.04 5.31 ( 0.05 k(253 K) = 5.30 ( 0.04d 5.09 ( 0.04 5.13 ( 0.07 k(270 K) = 5.11 ( 0.04d 4.95 ( 0.03 5.12 ( 0.08 4.89 ( 0.05 4.88 ( 0.04 5.11 ( 0.04 4.92 ( 0.07 4.87 ( 0.03 4.92 ( 0.04 4.94 ( 0.08 k(296 K) = 4.91 ( 0.02d 4.92 ( 0.04 4.86 ( 0.02 4.90 ( 0.04 4.92 ( 0.05 k(338 K) = 4.88 ( 0.02d 4.90 ( 0.03 5.05 ( 0.09 ARTICLE The Journal of Physical Chemistry A The Journal of Physical Chemistry A Table 1. Continued T P (K) (Torr) bath gas [O2] (1016 molecules cm3) v (cm s1) photolysis laser fluence (mJ cm2 pulse1) [precursor] (1014 molecules cm3) [OH]0 (1011 molecules cm3) [Z-CF3CHdCHCF3] (1015 molecules cm3) kc (1013 cm3 molecule1 s1) 374 200 He 8.6 15.1 0.40 1.34b 0.4618.1 4.94 ( 0.03 374 200 He 3.13 8.6 15.1 0.40 1.34b 0.7617.2 4.90 ( 0.04 374 50 N2 9.8 17.3 0.93 3.60b 0.8016.0 4.94 ( 0.04 374 50 N2 2.72 10 17.3 0.93 3.60b 0.2311.4 4.92 ( 0.04 k(374 K) = 4.94 ( 0.05d a (CH3)3COOH was used as the OH precursor. b H2O2 was used as the OH source. c The quoted uncertainties are the 2 precision from the linear least-squares fit of k0 versus [(Z)-CF3CHdCHCF3]. d Determined from a weighted linear least-squares fit to all (k0 kd) versus [(Z)-CF3CHdCHCF3]. 10543 dx.doi.org/10.1021/jp206195g |J. Phys. Chem. A 2011, 115, 10539-10549 Table 2. Summary of Experimental Conditions and Rate Coefficients Obtained for the OD + (Z)-CF3CHdCHCF3 Reaction T P [O2] v photolysis laser fluence [O3] [D2O] [OH]0 [Z-CF3CHdCHCF3] ka (K) (Torr, He) (1016 molecules cm3) (cm s1) (mJ cm2 pulse1) (1012 molecules cm3) (1016molecules cm3) (1011 molecules cm3) (1015 molecules cm3) (1013 cm3 molecule1 s1) 262 100 9.0 5.6 262 100 3.08 9.0 5.6 3.83 3.06 3.83 3.06 5.7 0.3813.7 5.7 0.3814.1 275 100 8.8 8.1 275 100 3.13 8.8 8.1 3.91 3.11 3.91 3.11 8.4 0.5615.1 8.4 0.4615.4 296 100 296 100 10.2 5.7 2.70 10.2 5.7 3.34 2.73 3.34 2.73 5.1 0.3314.9 5.1 0.4213.6 339 100 11.8 5.6 4.2 2.38 6.5 0.5316.2 339 100 2.35 11.8 5.6 4.2 2.38 6.5 0.8914.1 374 100 374 100 12.8 5.7 2.20 12.8 5.7 2.71 2.17 2.71 2.17 4.1 0.3218.2 4.1 0.2916.0 a The quoted uncertainties are at the 2 level from the precision of the fit. b Determined from a weighted linear least-squares fit of all (k0 kd) data versus concentration. 6.51 ( 0.07 6.45 ( 0.07 k(262 K) = 6.47 ( 0.06b 6.10 ( 0.09 6.13 ( 0.08 k(275 K) = 6.11 ( 0.07b 5.71 ( 0.09 5.75 ( 0.04 k(296 K) = 5.73 ( 0.07b 5.48 ( 0.03 5.40 ( 0.03 k(339 K) = 5.46 ( 0.04b 5.41 ( 0.05 5.43 ( 0.04 k(374 K) = 5.41 ( 0.04b ARTICLE The Journal of Physical Chemistry A ARTICLE Figure 1. Pseudo-first-order rate coefficient data for the reaction of OH with (Z)-CF3CHdCHCF3 at 296 K and the temperature extremes included in this study, 212 and 374 K. The lines are linear least-squares fits of the data to eq I. Infrared absorption spectra were recorded using a FTIR equipped with a low-volume multipass absorption cell (750 cm3, 485 cm optical path length). Spectra were measured between 500 and 4000 cm1 with a spectral resolution of 1 cm1. During the PLPLIF kinetic experiments, infrared absorption measurements were made either before or after the LIF reactor. 2.5. Materials. He (UHP, 99.999%), N2 (UHP, 99.99%), N2 (UHP, O2 < 0.5 ppm), and O2 (UHP, 99.99%) were used as supplied. Concentrated H2O2 (>95% mole fraction) was prepared by bubbling N2 for several days through a sample that was initially 60% mole fraction. The (CH3)3COOH sample (70 wt% in H2O) was obtained commercially. H2O2 and (CH3)3COOH were introduced into the gas flow by passing a small flow of He through a bubbler containing the liquid samples. The gas-phase composition from the (CH3)3COOH sample was approximately 56% (CH3)3COOH and 44% H2O.10 H2O2 and (CH3)3COOH were added to the main gas flow just prior to entering the LIF reactor. (Z)-CF3CHdCHCF3 (99.95%) samples were degassed in several freezepumpthaw cycles before use. The (Z)-CF3CHd CHCF3 sample was analyzed using gas chromatography and found to include the following minor impurities: (E)-CF3CHd CHCF3 (0.0037 wt %), (Z)-2-chloro-1,1,1,4,4,4-hexafluoro-2-butene (0.0001 wt%), (E)-1,1,1,4,4-pentafluoro-2-butene (0.0059%), (Z)-1-chloro-1,1,4,4,4-pentafluoro-2-butene (0.0019%), and saturated fluorocarbons (0.0038%). Mixtures of (Z)-CF3CHd CHCF3 in a He bath gas of between 10 and 35% were prepared manometrically in 12 L Pyrex bulbs for use in the OH rate coefficient measurements. The bulb content was monitored using infrared absorption and found to be stable, to within 1%, over a period of several weeks. Gas flows were measured with calibrated electronic mass flow meters and pressures were measured using 10, 100, and 1000 Torr capacitance manometers. The photolysis and probe lasers were operated at 10 Hz repetition rate. The gas flow velocity was in the range of 620 cm s1, ensuring a fresh sample of gas in the Figure 2. Temperature dependence of the rate coefficients for the OH and OD reactions with (Z)-CF3CHdCHCF3: OH reaction (filled circles), pulsed laser photolysislaser induced fluorescence (PLPLIF) technique (circles), and relative rate technique (RR) (triangles); OD reaction (open circles) obtained using the PLPLIF technique. The PLPLIF and RR data include the 2 uncertainty from the precision of the measurements. The lines are the least-squares fits of the PLPLIF data to the expression k(T) = AT2 exp(E/RT). LIF reaction volume for each photolysis pulse. The uncertainties quoted herein are at the 2 (95% confidence) level unless noted otherwise. 3. RESULTS AND DISCUSSION The rate coefficient results obtained using the PLPLIF technique for reactions 1 and 2 and the RR technique for reaction 1 are presented separately below. The results are then compared with rate coefficient data for several similar unsaturated fluorinated compounds. Finally, an atmospheric degradation mechanism of (Z)-CF3CHdCHCF3 under typical atmospheric conditions as well as its radiative efficiency and GWPs are presented. 3.1. OH and OD Reaction Rate Coefficients Obtained Using PLPLIF. Rate coefficients for reaction 1 were measured over the temperature range of 212374 K at pressures between 20 and 200 Torr. A summary of the experimental conditions and the rate coefficients obtained is given in Tables 1 and 2. The rate coefficients were found to be independent of pressure, within the precision of the measurements, at all temperatures included in this study. The OH and OD decay profiles followed pseudo-firstorder kinetics, that is, single-exponential decays over at least a 2 orders of magnitude decrease from the initial radical concentration under all experimental conditions. Representative experimental data are provided in the Supporting Information. Figure 1 shows a summary of the second-order rate coefficient data for reaction 1 obtained at 296 K and the temperature extremes included in this study, 212 and 374 K. The (k0 kd) values varied linearly with the (Z)-CF3CHdCHCF3 concentration over a range of experimental conditions such as [OH]0, 10544 dx.doi.org/10.1021/jp206195g |J. Phys. Chem. A 2011, 115, 10539-10549 The Journal of Physical Chemistry A ARTICLE Table 3. Summary of OH + (Z)-CF3CHdCHCF3 Reaction Rate Coefficients Obtained in This Work Using a RR Technique T (K) reference compounda k1/krefb k1(T)c (1013 cm3 molecule1 s1) 296 K C2H6 2.10 ( 0.04 5.25 ( 0.78 2.04 ( 0.03 5.11 ( 0.77 345 K C2H6 1.24 ( 0.02 4.94 ( 0.89 375 K C2H6 1.02 ( 0.02 5.15 ( 1.29 a k(298 K) = 2.5 1013 cm3 molecule1 s1 and k(T) = 7.66 1012 exp[1020/T] cm3 molecule1 s1 for OH + C2H6.9 b Quoted uncertainties are at the 2 level from the precision of the linear leastsquares fit of the data. c Quoted uncertainties are at the 2 level and include the 2 estimated systematic error in the reference reaction rate coefficient. Figure 3. RR data for the OH + (Z)-CF3CHdCHCF3 reaction at 296, 345, and 375 K and 100 Torr (He) relative to the OH + C2H6 reaction. The lines are least-squares fits of the data yielding the rate coefficient ratios given in Table 3. photolysis laser fluence, OH radical precursor, and linear gas flow velocity as outlined in Tables 1 and 2. The measured rate coefficients were also found to be independent of O2 addition to the reaction mixture. In the final analysis, k1(T) was obtained from a weighted linear least-squares fit of all data obtained at a given temperature, eq I. The fits shown in Figure 1 reproduce the experimental data very well with k1(296 K) = (4.91 ( 0.02) 1013 cm3 molecule1 s1, where the quoted uncertainty is from the precision of the fit. Figure 2 shows the temperature dependence of the measured rate coefficients for reaction 1. k1(T) has a non-Arrhenius behavior over the temperature range of 212374 K, where the reaction is nearly independent of temperature between 296 and 374 K but has a weak negative temperature dependence at temperatures below 296 K. k1(T) is well represented over the entire range of temperatures included in this study using the expression k1(T) = AT2 exp(E/RT). A linear least-squares fit of the individually measured rate coefficient data given in Table 1, 34 data points, using the expression ln(k1(T)) 2 ln(T) = ln(A) E/RT yielded k1(T) = (5.73 ( 0.10) 1019 T2 exp[(678 ( 5)/T] cm3 molecule1 s1, where the quoted uncertainties are from the precision of the fit. A least-squares fit of the rate coefficient data at temperatures e 300 K to an Arrhenius expression yields k1(T < 300 K) = (2.63 ( 0.16) 1013 exp[(185 ( 15)/T] cm3 molecule1 s1, where the quoted uncertainties are from the precision of the fit, which would be appropriate for use in atmospheric model calculations. Rate coefficients for the OD + (Z)-CF3CHdCHCF3 (k2) reaction were measured over the temperature range of 262 374 K. A summary of the experimental conditions and rate coefficients obtained is given in Table 2. Combining all of the results obtained at 296 K yields k2(296 K) = (5.73 ( 0.07) 1013 cm3 molecule1 s1, where the quoted uncertainties are from the precision of the fit to eq I. k2(T) is systematically greater than the rate coefficient obtained for the OH reaction by 15%. The larger rate coefficient for the OD reaction is similar to that reported recently from our laboratory for the OH/OD reactions with CH2dCHF and CH2dCF2.13 The temperature dependence of the reaction 2 rate coefficient is similar to that of reaction 1 with k2(T) = (4.81 ( 0.20) 1019 T2 exp[(776 ( 15)/T], where the quoted uncertainties are from the precision of the fit. The rate coefficient data for reaction 2 are included in Figure 2 for comparison with the rate coefficients obtained for the OH reaction. 3.2. RR Measurements. Figure 3 shows the results obtained in the RR coefficient measurements for reaction 1 at 296, 345, and 375 K. The loss of (Z)-CF3CHdCHCF3 relative to the loss of C2H6 obeys eq II to within the precision of the measurements. A linear least-squares fit to the data yielded kZ/kC2H6 values of 2.10 ( 0.04, 1.24 ( 0.02, and 1.02 ( 0.02 at 296, 345, and 375 K, respectively, where the quoted uncertainties are from the precision of the fits. The results of the RR measurements are summarized in Table 3 and included in Figure 2 for comparison with our absolute rate coefficient results. The results obtained using the two techniques agree to within the measurement precision at all temperatures. 3.3. O3 Reaction Rate Coefficients. The room-temperature (296 K) rate coefficient for the reaction of O3 with (Z)-CF3CHd CHCF3 O3 Z-CF3CHdCHCF3 f Products 7 was measured by monitoring the loss of (Z)-CF3CHdCHCF3 in the presence of excess O3. There was no observable change, <0.5%, in the (Z)-CF3CHdCHCF3 concentration in the reactor in the absence of O3, but under otherwise identical conditions. O3 loss of as much as 30% was, however, observed over the 13 h duration of an experiment, which was also observed under similar conditions in the absence of (Z)-CF3CHdCHCF3. An average O3 concentration was used in the analysis. The experimental data are given in the Supporting Information. We observed an increase in the measured rate coefficient when O2 was added to the reaction mixture. It should be noted that O2 was also present in the reactor as an impurity in the O3 sample, but at a lower concentration than that added directly. The increase of k7(296 K) in the presence of O2 suggests that secondary chemistry possibly played a role under these conditions. In the absence of added O2, k7(296 K) = (1.2 ( 0.3) 1021 cm3 molecule1 s1 was obtained from a fit of the (Z)-CF3CHdCHCF3 loss to eq I, where the uncertainty is from the precision of the fit. In the 10545 dx.doi.org/10.1021/jp206195g |J. Phys. Chem. A 2011, 115, 10539-10549 The Journal of Physical Chemistry A ARTICLE Table 4. Summary of the Rate Coefficient Data for the Reaction of OH with (Z)-CF3CHdCHCF3 and Comparison with Rate Coefficients of Structurally Similar Species compound k(296 K) (1013 cm3 molecule1 s1) k(T) (cm3 molecule1 s1) methoda pressure range (Torr) temperature range (K) reference (Z)-CF3CHdCHCF3 4.91 ( 0.50b (5.73 ( 0.60) 1019 T2 PLPLIF 20200 (He, N2) 212374 this work exp[(678 ( 10)/T]c 5.18 ( 0.46b RRFTIR 100 (He) 296 this work CF3CFdCFCF3 4.82 ( 1.15d RRFTIR 700 (N2) 296 Young et al.14 CF3CFdCFCF3 3.7 ( 0.2e RRGC 750 (N2) 298 Cometto et al.18 (Z)-CF3CFdCFCF3 3.80 ( 0.04 f PLPRF 30100 (Ar) 230370 Orkin et al.15 (E)-CF3CFdCFCF3 5.86 ( 0.06 f PLPRF 30100 (Ar) 230370 Orkin et al.15 (E)-CF3CHdCHF 9.25 ( 1.72 RRFTIR 700 (Air) 296 Sondergaard et al.16 CF3CHdCH2 15.2 ( 0.5 FPRF 100 (Ar) 296 Orkin et al.17 CF3CF2CFdCF2 19.4 ( 2.7 RRFTIR 700 (N2) 296 Young et al.14 CF3CFdCF2 22.1 ( 0.8g (5.66 ( 1.4) 1013 FPRF 100 (Ar) 252370 Orkin et al.17 exp[(407 ( 85)/T]f,g 21.6 ( 0.7g f FPRF 30100 (Ar) 230480 Orkin et al.15 CH2dCF2 27.9 ( 2.5b (1.75 ( 0.20) 1012 PLPLIF 20600 (He, N2) 220375 Baasandorj et al.13 exp[(140 ( 20)/T]c CH2dCHF 51.8 ( 5.0b (1.75 ( 0.20) 1012 PLPLIF 20600 (He, N2) 220375 Baasandorj et al.13 exp[(316 ( 25)/T]c CF2dCF2 99.8 ( 1.5g (3.39 ( 0.22) 1012 FPRF 100 (Ar) 250370 Orkin et al.29 exp[(323 ( 11)/T]g a PLPLIF: pulsed laser photolysislaser-induced fluorescence; RRFTIR: relative rate technique using Fourier transform infrared spectroscopy detection; RRGC: relative rate technique using gas chromatography detection; Rec: recommendation. b Uncertainties are at the 2 level and include estimated systematic errors. c The uncertainty in the pre-exponential term includes the estimated systematic errors. The uncertainty in the exponential term is at the 2 level from the precision of the least-squares fit (rounded off). d Reported as the rate coefficient for both (Z)- and (E)- isomers. e Reported rate coefficient obtained using a mixture of isomers. f Non-Arrhenius expressions were reported: 2.99 1014 (T/298)2.61 exp[760/T] cm3 molecule1 s1 for (Z)-CF3CFdCFCF3, 7.50 1014 (T/298)1.68 exp[612/T] cm3 molecule1 s1 for (E)-CF3CFdCFCF3, and 9.75 1014 (T/298)1.94 exp[922/T] cm3 molecule1 s1 for CF3CFdCF2. g Uncertainties are at the 2 level and do not include estimated systematic errors. presence of 9.7 1015 molecules cm3 O2, k7(296 K) was found to be (4.5 ( 1.2) 1021 cm3 molecule1 s1. 3.4. Error Analysis. Kinetic measurements were carried out over a range of experimental conditions using different bath gases (He, N2), OH precursors, initial OH concentrations, gas flow velocities, and probe and photolysis laser fluences, as outlined in Tables 1 and 2. The uncertainty in the experimental variables was small, (1% in pressure, (2% in flow rate, and (1 K in temperature. The precision of the measurements was high, with rate coefficients measured under different experimental conditions at a given temperature agreeing to better than 2%. In the PLPLIF experiments, the (Z)-CF3CHdCHCF3 concentration was determined online using infrared and UV absorption measurements as well as measured gas flows. The three measurements agreed to better than 6% under all experimental conditions. This includes infrared absorption measurements made before and after the LIF reactor that demonstrated no significant loss of the (Z)-CF3CHdCHCF3 as it flowed through the apparatus. The uncertainty in the determination of the absorption cross sections was <3%. A GC analysis of the (Z)-CF3CHdCHCF3 sample did not identify any impurities that would significantly influence the rate coefficient measurement. The good agreement in the rate coefficients obtained with the PLPLIF and RR methods also indicates that sample impurities did not significantly influence the rate coefficient determination at temperatures g 296 K. The absolute uncertainty in the rate coefficient obtained using the RR method was primarily determined by the uncertainty in the reference compound rate coefficient, where the estimated uncertainty in the OH + C2H6 reaction rate coefficient is currently estimated to be 7% at 298 K and 11% at 375 K (1).9 On the basis of the measurement precision and estimated systematic errors, the overall uncertainty in the absolute rate coefficients is estimated to be 9%. The recommended rate coefficients from this work are k1(T) = (5.73 ( 0.60) 1019 T2 exp[(678 ( 5)/T] cm3 molecule1 s1 and k2(T) = (4.81 ( 0.20) 1019 T2 exp[(776 ( 15)/T], where the measured room-temperature rate coefficients are k1(296 K) = (4.91 ( 0.50) 1013 cm3 molecule1 s1 and k2(296 K) = (5.73 ( 0.50) 1013 cm3 molecule1 s1. The rate coefficient for reaction 1 over the range of temperatures most relevant for atmospheric chemistry can be expressed using an Arrhenius expression as k1(T < 300 K) = (2.63 ( 0.40) 1013 exp[(185 ( 15)/T] cm3 molecule1 s1. The uncertainty due to estimated systematic errors is included in the pre-exponential terms. 3.5. Rate Coefficient Comparison. To our knowledge, there are no OH radical kinetic studies currently available for hydrofluorobutenes, although studies of the perfluorobutenes CF3CFd CFCF3 and CF3CF2CFdCF2 have been published.14,15 Here, we compare the reactivity of (Z)-CF3CHdCHCF3 with similarly structured hydrofluoro-olefins and perfluorobutenes. Table 4 provides a summary of rate coefficient data for several compounds structurally similar to (Z)-CF3CHdCHCF3. As with the reaction of OH with olefins, it seems reasonable to assume that reaction 1 proceeds via OH addition to the double bond in (Z)-CF3CHdCHCF3. The perfluorinated compounds 10546 dx.doi.org/10.1021/jp206195g |J. Phys. Chem. A 2011, 115, 10539-10549 The Journal of Physical Chemistry A Figure 4. Simplified atmospheric degradation mechanism for (Z)CF3CHdCHCF3 under high NOx conditions following initiation by reaction with the OH radical. The species enclosed in boxes are the expected stable atmospheric end products. ARTICLE counterparts.13,1517 However, the room-temperature rate coefficients for (Z)-CF3CHdCHCF3 and (Z)-CF3CF=CFCF314,15,18 are more similar in magnitude, 4.9 1013 and 3.8 1013 cm3 molecule1 s1,15 respectively. (Z)-CF3CHdCHCF3 is less reactive than C2C3 hydrofluoralkenes and CF3CF2CFdCF2. The decreased OH radical reactivity of the fluorinated 2-butenes is partially the result of fluorine substitution to an olefinic carbon, which leads to a reduction in OH reactivity due to the strong electron-withdrawing effect of fluorine. For example, CH2d CHF and trans-CF3CHdCHF are a factor of 1.6 less reactive than CH2dCH2 and CF3CHdCH2, respectively. Substitution of a CF3 group for a F atom on a carbon in the >CdC< bond results in a more pronounced reduction in reactivity, which is attributed to a combination of electron withdrawing as well as steric hindrance by the CF3 group. For example, a factor of 20 decrease in the 296 K rate coefficient is observed between CF2dCF2,17,19 CF3CFdCF2,17 and CF3CFdCFCF3.14,15 The deactivating effect of the CF3 group, however, has only been observed for substitution directly at the carbon atom of the >CdC< double bond. Vesine et al.20 reported that substitution of C4F9 or C6F13 groups for the CF3 group in CF3CHdCH2 did not lead to a significant change in OH reactivity. These qualitative trends in OH reactivity in part explain the difference in reactivity between perfluoro-1-butene and the partially fluorinated 2-butenes. OH radical reactions with C2 and C3 hydrofluoroalkenes13,17,20 have a negative temperature dependence over the temperature range of 215380 K that is consistent with a reaction mechanism involving OH addition to the carboncarbon double bond. In the present study, k1(T) was found to have a weak dependence on temperature and a weak non-Arrhenius behavior between 212 and 374 K. The non-Arrhenius behavior is similar to that observed for the reaction of OH with (Z)-CF3CF=CHF, as reported in a previous study from our laboratory.6 NonArrhenius behavior is sometimes associated with a change of the reaction mechanism, that is, a mechanism dominated by OH radical addition at low temperature with an increasing contribution from H atom abstraction at higher temperatures. However, in the case of reaction, a shift in reaction mechanism is not likely over the limited temperature range included in this study because of the large activation energy associated with the abstraction reaction.21 Further research is needed to identify the details of the reaction mechanism and its temperature dependence. Figure 5. Infrared spectrum (base e) of (Z)-CF3CHdCHCF3 measured at 296 K using Fourier transform infrared spectroscopy at 1 cm1 resolution. CF2dCF2 and CF3CFdCF2 are significantly more reactive toward the OH radical than their partially fluorinated 4. ATMOSPHERIC IMPLICATIONS On the basis of the rate coefficients determined in this study, the atmospheric lifetime of (Z)-CF3CHdCHCF3 with respect to OH radical reaction is 22 days for an OH concentration of 1 106 molecules cm3 using k1(272 K).22 The atmospheric lifetime of (Z)-CF3CHdCHCF3 should be considered an approximate value because its actual loss will be highly dependent on the actual time and location of its emission and the associated variations in the OH radical abundance. The O3 + (Z)-CF3CHd CHCF3 reaction rate coefficient at 296 K was found to be <6 1021 cm3 molecule1 s1, making atmospheric loss due to reaction with O3 a minor process (lifetime > 3 years for an O3 abundance of 50 ppm). The absorption cross section at 253.6 nm determined in this work, <4 1024 cm2 molecule1, establishes that UV photolysis is a negligible tropospheric loss process for (Z)-CF3CHdCHCF3. 10547 dx.doi.org/10.1021/jp206195g |J. Phys. Chem. A 2011, 115, 10539-10549 The Journal of Physical Chemistry A ARTICLE An atmospheric degradation mechanism for CF3CH=CHCF3, which is based on analogous well-established hydrocarbon chemistry, under high NO,, conditions is outlined in Figure 4. Under these conditions, the RO2 radicals formed in the initial steps of the mechanism will primarily react with NO to yield a fluorohydroxyalkoxy (RO) radical or fluorohydroxyperoxynitrate. Unimolecular decomposition of the alkoxy radical via scission of the central carbon --carbon bond leads to the formation of CF3CHO, while scission of the terminal carbon --carbon bond yields CF3CH(OH)CHO and CF2O. Reaction of RO2 radicals with NO2 could also lead to the formation of fluoroperoxynitrates. CF2O, CF3CHO, CO2, and CO were the only end products observed in our RR experiments, which were performed under NOx-free conditions. In the atmosphere, the CF3CH(OH)CHO and CF3CH(OH)C(O)CF3 end products are expected to be short-lived, although no laboratory studies of these species are currently available. CF2O is removed from the atmosphere primarily via wet deposition and rainout.4'23 CF3CHO is removed from the atmosphere blr UV photolysis24'25 (<25 day lifetime) and reaction with OH 5'26 ("'20 day lifetime). Therefore, the gas-phase degradation of (Z)-CF3CH=CHCF3 is not expected to lead to a significant formation of atmospherically long-lived species. The photochemical ozone creation potential (POCP) of (Z)CF3CH=CHCF3 was estimated using the method described by Derwent et al.27 to be 3.4. This is much lower than the POCPs of similar hydrocarbon alkenes, for example, POCPs are 112 for CH3CH=CH2 and 107.9 for CH3CH2CH=CH2.27 The contribution of (Z)-CF3CH=CHCF3 to regional photochemical ozone formation is, therefore, expected to be small, while the actual contribution would be dependent on its atmospheric abundance. 4.1. Global Warming Potentials (GWPs). The infrared absorption spectrum of (Z)-CF3CH=CHCF3 measured in this work at 296 K is given in Figure 5. The (Z)-CF3CH= CHCF3 spectrum measured over the concentration range of (0.70-21.1) x 1014 molecules cm-3 obeyed Beer's law, varied linearly with concentration, and was independent of bath gas pressure (30-500 Torr, He). Absorption band strengths were determined by a linear least-squares analysis of the integrated absorbance versus [(Z)-CF3CH=CHCF3]. Integrated band strengths over the ranges of 1100-1280 and 1280-1500 cm-1 were determined to be 21.5 0.12 and 6.26 0.02 (in units of 10-17 cm2 molecule-1 cm-1), respectively, where the uncertainties are from the precision of the linear least-squares fit of the integrated absorbance versus concentration. The radiative efficiency (RE) of (Z)CF3CH=CHCF3 was calculated to be 0.38 W m 2 ppb-1 using the approximation method given by Pinnock et al.28 For comparison, the RE of (Z)-CF3CH=CHCF3 is comparable to that of other unsaturated fluorinated butanes where the RE for CF3CF2CF2CF3 (petfluoro-butane) is 0.33 W m 2 ppb-1 1 and that for CF3CF= CFCF3 (perfluoro-2-butene) is 0.32 W m 2 ppb-1.14 The GWP of (Z)-CF3CH=CHCF3 was calculated relative to CO2 using the lifetimes and radiative efficiencies determined in this study and the integrated radiative forcing of CO2 given in WMO 2010.1 The GWPs of (Z)-CF3CH=CHCF3 for the 20, 100, and 500 year time horizons are 31, 8.9, and 2.7, respectively, using a (Z)-CF3CH=CHCF3 atmospheric lifetime of 22 days. 5. CONCLUSIONS Rate coefficients for the OH reaction with (Z)-CF3CH= CHCF3 were determined over a range of temperatures (212-375 K) and bath gas pressures (20-200 Torr). The rate coefficients were found to be independent of pressure over this range within the precision of the measurements. The measured rate coefficient is well represented by the expression k1(T) = (5.73 0.60) x 10-19 x T2 x exp[(678 f 10)/T] cm3 molecule-1 s-1, where the measured room-temperature rate coefficient was k1(296 = (4.91 0.50) x 10-1 cm3 molecule-1 s-1 and the quoted uncertainties are at the 2a (95% confidence) level and include estimated systematic errors. The room-temperature rate coefficient for the reaction of O3 with (Z)-CF3CH=CHCF3 was determined to be <6 x 10-21 cm3 molecule-1 s--1. The O3 reaction represents a minor atmospheric loss process for (Z)CF3CH=CHCF3. On the basis of the OH rate coefficients and infrared spectrum determined in this study, the atmospheric lifetime of (Z)-CF3CH=CHCF3 was estimated to be --20 days, and its global warming potential is --9 on the 100 year time horizon. ASSOCIATED CONTENT Supporting Information. Figures of OH radical pseudofirst-order decays, kinetic data for the O3 + (Z)-CF3CH= CHCF3 reaction, and tabulated (Z)-CF3CH=CHCF3 infrared cross section data. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author *E-mail: @noaa.gov. ACKNOWLEDGMENT We thank Mark Robin and Barbara Minor of DuPont Fluoroproducts for providing the samples and sample purity analysis. This work was supported in part by NOAA's Climate Goal. REFERENCES (1) Scientific Assessment of Ozone Depletion: 2010, Global Ozone Research and Monitoring Project, Report No. 52; World Meteorological Organization (WMO), Geneva, Switzerland, http://ozone.unep.org/ Assessment_Panels/SAP/Scientific_Assessment_2010/index.shtml (2011), 516 pp. (2) IPCC/TEAP Special Report: Safeguarding the Ozone Layer and the Global Climate System: Issues Related to Hydrofluorocarbons and Perfluorocarbons Institution; Cambridge University Press: New York, 2005. (3) Kyoto Protocol to the United Nations Framework Convention on Climate Change., UNFCCC. http://unfccc.int/kyoto_protocol/items/ 2830.php (1997). (4) Velders, G. J. M.; Fahey, D. W.; Daniel, J. S.; McFarland, M.; Andersen, S. O. Proc. Natl. Acad. Sci. U.S.A. 2009, 106, 10949-10954. (5) Davis, M. E.; Gilles, M. K.; Ravishankara, A. R.; Burkholder, J. B. Phys. Chem. Chem. Phys. 2007, 9,2240-2248. (6) Papadimitriou, V. C.; Talukdar, R. K.; Portmann, R. W.; Ravishankara, A. R; Burkholder, J. B. Phys. Chem. Chem. Phys. 2008, 10, 808-820. (7) Papadimitriou, V. C.; Lazarou, Y. G.; Talukdar, R. K.; Burkholder, J. B. J. Phys. Chem. A 2011, 115, 167-181. (8) Papadimitriou, V. C.; Portmann, R. W.; Fahey, D. W.; Miihle, J.; Weiss, R. F.; Burkholder, J. B. J. Phys. Chem. A 2008, 112, 12657-12666. (9) Sander, S. P.; Abbatt, J.; Barker, J. R.; Burkholder, J. B.; Friecll, R. R.; Golden, D. M.; Huie, R. E.; Kolb, C. E.; Kurylo, M. J.; Moortgat, G. K.; Orkin, V. L.; Wine, P. H. Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies, Evaluation Number 17, JPL 10548 dx.doi.org/10.1021/jp206195g If Phys. Chem. A 2011, 115, 10539-10549 The Journal of Physical Chemistry A Publication 10-6; Jet Propulsion Laboratory, California Institute of Technology: Pasadena, CA, 2011; http://jpldataeval.jpl.nasa.gov. (10) Baasandorj, M.; Papanastasiou, D. K.; Talukdar, R. K.; Hasson, A. S.; Burkholder, J. B. Phys. Chem. Chem. Phys. 2010, 12, 12101-12111. (11) McCabe, D. C.; Rajakumar, B.; Marshall, P.; Smith, I. W. M.; Ravishankara, A. R. Phys. Chem. Chem. Phys. 2006, 8, 4563-4574. (12) Rothman, L. S.; Gordon, I. E.; Barbe, A.; Benner, D. C.; Bernath, P. E.; Birk, M.; Boudon, V.; Brown, L. R.; Campargue, A.; Champion, J. P.; Chance, K.; Coudert, L. H.; Dana, V.; Devi, V. M.; Fally, S.; Flaud, J. M.; Gamache, R. R.; Goldman, A.; Jacquemart, D.; Kleiner, I.; Lacome, N.; Lafferty, W. J.; Mandin, J. Y.; Massie, S. T.; Mikhailenko, S. N.; Miller, C. E.; Moazzen-Ahmadi, N.; Naumenko, O. V.; Nikitin, A. V.; Orphal, J.; Perevalov, V. I.; Perrin, A.; Predoi-Cross, A.; Rinsland, C. P.; Rotger, M.; Simeckova, M.; Smith, M. A. H.; Sung, K.; Tashkun, S. A.; Tennyson, J.; Toth, R. A.; Vandaele, A. C.; Vander Auwera, J. J. Quant. Spectrosc. Radiat. Transfer 2009, 110, 533-572. (13) Baasandorj, M.; Knight, G.; Papadimitriou, V. C.; Talukdar, R. K.; Ravishankara, A. R.; Burkholder, J. B. J. Phys. Chem. A 2010, 114, 4619-4633. (14) Young, C. J.; Hurley, M. D.; Wallington, T. J.; Mabury, S. A. Atmos. Environ. 2009, 43, 3717-3724. (15) Orkin, V. L.; Poskrebyshev, G. A.; Kurylo, M. J. J. Phys. Chem. A 2011, 115, 6568-6574. (16) Sondergaard, R.; Nielsen, O. J.; Hurley, M. D.; Wallington, T. J.; Singh, R. Chem. Phys. Lett. 2007, 443, 199-204. (17) Orkin, V. L.; Huie, R. E.; Kurylo, M. J. J. Phys. Chem. A 1997, 101, 9118-9124. (18) Cometto, P. M.; Taccone, R. A.; Nieto, J. D.; Dalmasso, P. R.; Lane, S. I. ChemPhysChem 2010, 11, 4053-4059. (19) Acerboni, G.; Jensen, N. R.; Rindone, B.; Hjorth, J. Chem. Phys. Lett. 1999, 309, 364-368. (20) Vesine, E.; Bossoutrot, V.; Mellouki, A.; Bras, G. L.; Wenger, J.; Sidebottom, H. J. Phys. Chem. A 2000, 104, 8512-8520. (21) Atkinson, R. Chem. Rev. 1986, 86, 69-201. (22) Prinn, R. G.; Huang, J.; Weiss, R. F.; Cunnold, D. M.; Fraser, P. J.; Simmonds, P. G.; McCulloch, A.; Harth, C.; Salameh, P.; O'Doherty, S.; Wang, R. H. J.; Porter, L.; Miller, B. R. Science 2001, 292, 1882-1888. (23) Wallington, T. J.; Schneider, W. F.; Worsnop, D. R.; Nielsen, O. J.; Sehested, J.; Debruyn, W. J.; Shorter, J. A. Environ. Sci. Technol. 1994, 28, A320-A326. (24) Chiappero, M. S.; Malanca, F. E.; Arguello, G. A.; Wooldridge, S. T.; Hurley, M. D.; Ball, J. C.; Wallington, T. J.; Waterland, R. L.; Buck, R. C. J. Phys. Chem. A 2006, 110, 11944-11953. (25) Sellevag, S. R.; Kelly, T.; Sidebottom, H.; Nielsen, C. J. Phys. Chem. Chem. Phys. 2004, 6, 1243-1252. (26) Atkinson, R.; Baulch, D. L.; Cox, R. A.; Crowley, J. N.; Hampson, R. F.; Hynes, R. G.; Jenkin, M. E.; Rossi, M. J.; Troe, J. Atmos. Chem. Phys. 2006, 6, 3625-4055. (27) Derwent, R. G.; Jenkin, M. E.; Saunders, S. M.; Pilling, M. J. Atmos. Environ. 1998, 32, 2429-2441. (28) Pinnock, S.; Hurley, M. D.; Shine, K. P.; Wallington, T. J.; Smyth, T. J. J. Geophys. Res. 1995, 100, 23227-23238. (29) Orkin, V. L.; Louis, F.; Huie, R. E.; Kurylo, M. J. J. Phys. Chem. A 2002, 106, 10195-10199. ARTICLE 10549 dx.doi.org/10.1021/jp206195g |J. Phys. Chem. A 2011, 115, 10539-10549