1,1,1,2,2,3,3-heptafluoro-3-[(trifluorovinyl)oxy]propane

Phototransformation in air

Administrative data

Endpoint:

phototransformation in air

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2015

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Data source

Reference

Reference Type:

publication

Title:

Kinetics and mechanism of the reaction of perfluoro propyl vinyl ether (PPVE, C3F7OCF=CF2) with OH: assessment of its fate in the atmosphere

Author:

Amedro D, Vereecken L, Crowley JN

Year:

2015

Bibliographic source:

Phys. Chem. Chem. Phys., 2015, 17, 18558–18566.

Report date:

2015

Materials and methods

Test guideline

Qualifier:

no guideline available

Principles of method if other than guideline:

Indirect phototransformation with *OH initiation.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

PPVE

IUPAC Name:

PPVE

Details on test material:

- Name of test material (as cited in study report): PPVE, perfluoropropylvinylether
- Physical state: clear colorless liquid

Specific details on test material used for the study:

Purity 99.85%, further purified by degassing

Study design

Light source:

other: KrF excimer laser

Light spectrum: wavelength in nm:

248

Details on light source:

Photolysis laser light for *OH generation was provided by a Lambda-Physik LPX 300 excimer laser (KrF, 248 nm), operating at a pulse frequency of 10 Hz with a fluence of 2-6 mJ/cm per pulse.

Details on test conditions:

Reactions were carried out in a thermostatically controlled reactor of 500 cm³, at pressures of either 50 Torr or 200 Torr using nitrogen or nitrogen/oxygen bath gas. Temperatures ranged from 212K to 298K. Gas flow rates, regulated using calibrated mass flow controllers, were between 550 and 2200 cm³(STP)/ min (sccm). Either H2O2 or HNO3 was used as *OH precursor with laser photolysis at 248 nm. Concentration of *OH was measured by UV fluorescence directly in the reaction chamber after photoexcitation by a YAG-pumped dye laser at 282 nm. Following excitation of the OH A²Σ(n' = 1) ← X2π(n' = 0) transition (Q11(1) at 281.997 nm), fluorescence was detected by a photomultiplier tube (PMT) screened by a 309 nm interference filter and a BG 26 glass cut-off filter. The detection llimit in the absence of PPVE was determined by the photolysis of a known amount of H2O2 or HNO3 with a known laser fluence and found to be ca 1E9/cm³ for a S/N = 1 (25 scans). Concentration of PPVE was measured in a downstream, room-temperature UV absorbance cell (43.8 cm) at 184.95 nm. Concentration of H2O2 was measured in a tandem UV cell (34.8 cm) at 213.86 nm. HNO3 was used as *OH source at lower reaction temperatures, in which case HNO3 concentration was measured in the 184.95 nm cell. When HNO3 was present, PPPVE concentration could not be measured accurately due to interference by HNO3. In this event, PPVE concentration was estimated using calibrated PPVE flows at the mass flow controller. PPVE concentration was far in excess of *OH throughout the experiment, allowing each reaction to be considered pseudo-first order in [*OH] as
[OH]t = [OH]0 * exp[-k't]
where k' is the pseudo-first order rate constant defined by
k' = k[PPVE] + kd
k is the bimolecular rate coefficient (cm³/ molecule∙ s1) for the reaction between PPVE and OH, and kd (/s) accounts for both OH-losses due to diffusion of OH out of the reaction zone and side reactions. The bimolecular constant k was determined as the slope of the linear fit of k' v. [PPVE], and kd was determined as the intercept.

Reference substance:

no

Remarks:

Study used an absolute method, no reference substance

Results and discussion

Degradation rate constant

Key result

Reaction with:

OH radicals

Rate constant:

0 cm³ molecule-1 s-1

Remarks on result:

other: at 293.3K, 2σ error ± 0.06

Transformation products:

not measured

Any other information on results incl. tables

No change in rate coefficient in going from 50 to 200 Torr (at 298±1K) indicating that the high-pressure limit is already reached at 50 Torr of nitrogen. There is an inverse relationship of rate constant with temperature as described by a simple Arrhenius expression of the form k(T) = (4.88 ± 0.49) x 10^-13 exp[(564± 10)/T] for experiments in nitrogen.

Applicant's summary and conclusion

Validity criteria fulfilled:

not applicable

Conclusions:

The rate constant for reaction of PPVE with hydroxyl radicals at 293K is 3.36E-12 cm³/molecule∙s.

Executive summary:

Reaction of PPVE with hydroxyl radical (*OH) was measured using an absolute method, with laser excitation of precursor to form *OH. PPVE concentration was far in excess of *OH, allowing the reaction to be considered pseudo-first order in *OH concentration. Disappearance of *OH was used to monitor extent of reaction. *OH concentration was measured using laser fluorescence at 282 nm, while concentration of PPVE was measured in a downstream UV absorbance cell at 184.95 nm. Rate constants at a given temperature was determined as the slope of rate of *OH loss v. PPVE concentration. Reactions were conducted over a temperature range from 212K to 298K and at pressures of 50 or 200 Torr. No difference was observed at either pressure, indicated that the reaction was already at its high-pressure limit at 50 Torr. The reaction had an inverse relationship with temperature as described by a simple Arrhenius expression of the form k(T) = (4.88 ± 0.49) x 10^-13exp[(564± 10)/T] for experiments in nitrogen. The rate constant as measured at 293K is 3.36E-12 cm³/molecule∙s may be used to estimate a pseudo-first order rate constant is 0.145/day and estimated DT50 is 4.8 days.

The study was well-documented and conducted according to generally accepted scientific principles. However, as a scientific publication full details are lacking, and the study was not conducted under GLP. It is considered reliable with acceptable restriction, and is suitable for Risk Assessment, Classification & Labeling, and PBT Analysis.