Chlorotrifluoroethylene

Endpoint summary

Additional information

Chlorotrifluoroethylene (CTFE) is a volatile gas at ambient conditions with a boiling point in the range of -26.2°C (The Beilstein database. Reference: Miller - 1951) to -26.8°C (The Beilstein database. Reference: Henne - 1948) and a vapour pressure of 612 kPa at 25 °C (ISCS No. 0685, NIOSH).

A value of water solubility of 380 mg/l was experimentally determined in a completely sealed system with an atmosphere saturated with CTFE (Oriani R., 2001). The experimental test conditions did not represent the natural condition in the environment and therefore, although the value of 380 mg/l itself reveals a moderate water solubility, it represents an overestimation of the actual water solubility of CTFE in the natural system.

On the basis of the above quoted physico-chemicals properties, CTFE is expected to partition into atmosphere.

Even the Henry’s Law constant of 31,500 Pa m3/mol (HENRYWIN v.3.0, EPI Suite v.4.0) suggest that the substance is expected to rapidly volatise from water and soil to the air.

In order to evaluate the environmental fate of CTFE, a Level III fugacity model was conducted (EQC Fugacity III Model, v.2.02, May 2003), assuming steady-state but not equilibrium conditions.

The Level III Fugacity Model predicts partitioning between four environmental compartments (air, soil, sediment and water) using a combination of default parameters and various input physico-chemical parameters. The model was run assuming emissions only to air. In fact, in case of an accidental emission, CTFE is uniquely released to air, because of its volatility at ambient conditions and boiling point ranging from -26.2°C to -26.8°C. °C.

The environmental fate of the substance, assessed through the model, confirmed that, following emissions in air, CTFE remains in this compartment. The rates of transfer to soil and water are very low and only negligible amounts of the total emission remain in these media and in sediment.

As far as the CTFE stability is concerned, in the atmosphere the substance is rapidly degraded by reaction with photochemically produced hydroxyl radicals with half-lives, determined from experimentally derived rate constants. A rate constant for the chlorine-atom initiated oxidation of chlorotrifluoroethylene in the atmosphere gives CClF2CF(O) as the major product; the quantum yield of oxidation for this reaction is >1000 relative to the quantum yield for olefin (Sanhueza E et al.1956), Reaction with ozone gives an estimated half-life of 715 days (Meylan W. M, 1993). The primary product of this reaction is the corresponding carbonyl product (Heicklen J. P.,1975). A rate constant of 2.7X10-11 cm cu/mol sec is reported for the reaction of chlorotrifluoroethylene with atomic oxygen (Heicklen J. P.,1975). C2F3Cl is NOT listed in the Scientific Assessment of Ozone Depletion of the World Metereological Organization/United nations Environment Programme (WMO/UNEP) or the Montreal Protocol as it is NOT considered as a substance contributing to the Ozone depletion (Laube J. C., 2008). A model prediction for evaluating the environmental fate of CTFE (EQC Fugacity III Model, v.2.02, May 2003) confirms that the whole amount of CTFE released to air remains in this compartment.

Hydrolysis studies cannot be conducted with volatile substances (section 2 of REACH Annex XI). However, although no partition into water is expected, the tendency to be hydrolyzed has been assessed basing on the chemical structure of CTFE molecule. This does not contain any functional groups associated with hydrolysis properties at relevant environmental conditions. Particularly, the carbon-fluorine bond is the strongest bond in organic chemistry (O'Hagan, 2008). Substitution of hydrogen atoms with fluorine results in increased bond strengths for both carbon-fluorine and adjacent carbon-carbon bonds over the corresponding hydrocarbon and would increase the resistance to hydrolysis (Lemal, 2003). Therefore, based on this qualitative structure-activity relationship, it can be concluded that hydrolysis is not a relevant degradation mechanism for this substance.

Although no release to the aquatic environment is expected on the basis of CTFE profile and on its environmental fate, a further assessment based on Quantitative Structure Activity Relationships (QSARs) has been however applied. 

In particular, the ready biodegradability of CTFE has been estimated with a model prediction BIOWIN v4.10, EPI Suite v.4.0 which result reports that the substance is not readily biodegradable.

No experimental bioaccumulation data are available for the substance; however, in order to evaluate the bioaccumulation hazard of profile of CTFE, the BCFBAF model v.3.0, EPI Suite v 4.0 has been applied.

The model prediction for CTFE yielded a BCF of 5.7, indicating that CTFE has a very low potential to bioaccumulate in aquatic organisms.

No releases to the soil are expected on the basis of CTFE profile and environmental fate, however the KOCWIN model v 2.0, EPI Suite v 4.0 has been applied in order to evaluate the soil adsorption hazard profile of CTFE.

On the basis of the model results, estimated both with the Molecular Connectivity Index (MCI) and with the log Kow (KOCWIN model v 2.0, EPI Suite v 4.0), it is deemed unlikely that CTFE can adsorb to sediment and particulates matter.

On the basis of the above reported evaluations, the substance is not expected to persist in the environment. In fact, the whole amount of CTFE released to air partitions in this compartment where it is readily photochemically degraded.