Trifluoro(trifluoromethoxy)ethylene

Phototransformation in air

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

phototransformation in air

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

The examinations are completed using a combination of discharge flow coupled with mass spectrometer and resonance fluorescence (DF/MS/RF). Fourier transform infrared (FTIR), ab initio molecular orbital calculation, and atmospheric and radiative transfer modeling.

GLP compliance:

no

Estimation method (if used):

The study examinated the reactivity of CF3OCFCF2 toward OH radical, its infrared spectroscopic properties, its atmospheric lifetime, its radiative forcing and its global warming potential. The examination is completed using a combination of discharge flow coupled with mass spectrometer and resonance fluorescence (DFIMSIRF), Fourier transform infrared (FTIR) spectroscopy, ab initio molecular orbital calculation, and atmospheric and radiative transfer modeling. Mass spectral evidence

Light source:

other: Resonance fluorescence

Light spectrum: wavelength in nm:

309

Details on light source:

The resonance lamp for the radiation of OH at 309 nm was built by microwave discharging —3 torr (400 Pa) of H2O/He mixture in a quartz tube.

Reference substance:

no

Preliminary study:

not applicable

DT50:

< 2.5 d

Reaction with:

OH radicals

Rate constant:

< 0 cm³ molecule-1 s-1

The reaction of CF3OCF=CF2 with OH radicals produced both HF and CF3OCFC(O)F as products. The detailed reaction mechanism is complex and may involve the formation of an adduct intermediate or a four-center transition state. The Arrhenius expression for CF3OCF=CF2 + OH is determined to be k1 = (6.4l ± 0.82) x l0^11exp[(-868 ± 40)/T] cm3 molecule^-1 s^-1 in the temperature range of 253-348 K. The atmospheric lifetime of CF3OCF=CF2 is then estimated to be less than 5 days due to the OH attack. The calculated vibrational frequencies using ab initio molecular orbital calculations were in good agreement with FTIR experimental observation for the CF3OCF=CF2 molecule. Both C-O and C-F stretching modes in the CF3OCF=CF2 contribute to prominent absorption in the atmospheric window region. The adjusted radiative forcing for the CF3OCF=CF2 was calculated to be 0.041 W m^-2 ppbv^-1. The Global Warming Potential for the CF3OCF=CF2 was predicted to be small (less than 0.01) due to the short atmospheric lifetime of this molecule.

The Global Warming Potential for CF₃OCF = CF₂is evaluated to be 0.004 for 100-year time horizon.

On the basis of this analysis it is not expect the use of CF3OCF=CF2 to lead to any significant impact on climate.

Validity criteria fulfilled:

not applicable

Reference 2

Endpoint:

phototransformation in air

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well documented study reporting sufficient details on the used experimental methodology.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Kinetic measurments have been carried out using the flash photolysis and laser photolysis method combined, respectively, with the laser-induced fluoreshence technique

GLP compliance:

no

Light source:

other: xenon flash lamp used in the flash photolysis method.

Light spectrum: wavelength in nm:

>= 180

Reaction with:

OH radicals

Rate constant:

< 0 cm³ molecule-1 s-1

The rate constants for the reactions of OH radicals with trifluoromethyl trifluorovinyl ether (CF3OCFCF2) have been measured over the temperature range 250 - 430 K.

The rate constants at 298K determined with the methods: flash photolysis of H2O, laser photolysis of N2O followed by O(1D) + H2O, laser photolysis of N2O followed by O(1D) + CH4 and laser photolysis of H2O2 are the following:

2.96 ± 0.04 x 10^12 cm3 molecule^-1 s^-1

2.92 ± 0.06 x 10^12 cm3 molecule^-1 s^-1

2.93 ± 0.06 x 10^12 cm3 molecule^-1 s^-1

2.88 ± 0.07 x 10^12 cm3 molecule^-1 s^-1

The Arrhenius rate constants have been determined as k(CF3OCFCF2) = 1.01_-0.04^+0.04x 10^-12 exp[(320 ± 10)/T.

Validity criteria fulfilled:

not applicable

Reference 3

Endpoint:

phototransformation in air

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well documented study reporting sufficient details on the used experimental methodology.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Smog chamber/FTIR tecniques were used to study the OH radical and Cl atom initiated oxidation of CF3OCFCF2. The rate constant of the reaction between CF3OCFCF2 and OH was determined using the ralative rate techniques.

GLP compliance:

no

Estimation method (if used):

not applicable

Light source:

other: fluorescent blacklamps

Details on light source:

The reactor was surrounded by 22 fluorescent blacklamps (GE F15T8-BL) which were used to photochemically initiate the experiments.

Details on test conditions:

All experiments were performed in a 140-liter Pyrex reactor interfaced to a Mattson Sirus 100 FTIR spectrometer.7 The optical path length of the infrared beam was 27.7 m.
The oxidation of CF3OCF=CF2 was initiated by reaction with OH radicals or Cl atoms which were generated by the photolysis of methylnitrite, or molecular chlorine, in 700 Torr total pressure of O2/N2 diluent at 295 +/- 2 K, respectively. Loss of CF3OCFdCF2 and the formation of products were measured by FTIR spectroscopy at a resolution of 0.25 cm-1.

Reference substance:

yes

Remarks:

C2H4, C2H2, and C2H5Cl

Key result

DT50:

4 d

Test condition:

estimated

Key result

Reaction with:

OH radicals

Rate constant:

0 cm³ molecule-1 s-1

Transformation products:

yes

No.:

#1

No.:

#2

No.:

#3

The atmospheric lifetime of CF3OCF=CF2 is determined by its reaction with OH radicals which occurs with a rate constant of k1 = (2.6 +/- 0.3) x 10^-12 cm3 molecule^-1 s^-1 at 296 K in 700 Torr of air. The atmospheric lifetime of CF3OCF=CF2 with respect to reaction with OH can be estimated using three pieces of information: the value of k1 given above, k(OH + CCl3CH3) = 1.0 x 10^-14 cm3 molecule^-1 s^- at 296 K, and the atmospheric lifetime of CCl3CH3 with respect to reaction with OH = 5.9 years.

This approach gives an atmospheric lifetime of CF3OCF=CF2 with respect to reaction with OH of 0.023 years (8 days).The OH radical initiated atmospheric oxidation of CF3- OCF=CF2 gives COF2, CF3OC(O)F, and FC(O)C(O)F in molar yields of 90, 53, and 40%. As with other fluorinated carbonyl compounds the atmospheric fate of COF2, CF3OC(O)F, and FC(O)C(O)F is expected to be incorporation into water droplets within a time frame of 5 - 15 days followed by hydrolysis to give HF and CO2.

The atmospheric degradation of CF3OCF=CF2 produces the same fluorinated radical species as formed during the degradation of HFCs. HFCs do not impact stratospheric ozone and the same conclusion applies to HFEs;CF3- OCF=CF2 has an ozone depletion potential of zero.

Finally, the authors considered the potential for CF3OCF=CF2 to impact the radiative balance in the atmosphere.The absorption cross section for CF3OCF=CF2 integrated over the range 1100 - 1200 cm^-1 is (2.67 +/- 0.30) x 10^-16 cm molecule^-1, quoted errors reflect our estimate of the total accuracy of the measurement, and is consistent with the previous determination of 2.48 x 10^-16 cm molecule^-1.

Validity criteria fulfilled:

not applicable

Conclusions:

The atmospheric lifetime of CF3OCF=CF2 is determined by its reaction with OH radicals which occurs with a rate constant of k1 = (2.6 +/- 0.3) 10^-12 cm3 molecule-1 s-1 at 296 K in 700 Torr of air. The atmospheric lifetime of CF3OCF=CF2 with respect to reaction with OH is estimated to be 0.023 years (8 days).

Description of key information

Rate constant with OH radicals = (2.6 +/- 0.3) x 10^-12 cm3 molecule-1s-1at 296 K in 700 Torr of air.
Atmospheric lifetime = 0.023 years (8 days)

Key value for chemical safety assessment

Half-life in air:

4 d

Degradation rate constant with OH radicals:

0 cm³ molecule-1 s-1

Additional information

Information regarding the atmospheric degradation of perfluoromethyl vinyl ether (PMVE) was sourced from three scientific articles.

All the studies agree on the fact that the rate constant of the reaction of PMVE with OH radicals is of 10^-12 cm3 molecule^-1s^-1 order of magnitudo and that its atmospheric life time is of few days (5 to 8 days).

The values selected as key information and above reported were sourced from the article of Mashino, M et al. since specific information, on both temperature and pressure at which the measurement has been conducted, are available.