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Environmental fate & pathways

Hydrolysis

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Description of key information

Basing on the physico-chemical properties and the environmental fate assessments of the molecule, the hydrolitic degradation of CTFE is neither measurable nor expected.

Key value for chemical safety assessment

Additional information

CTFE was assessed both for its physico-chemical properties and for its environmental fate. On the grounds of these assessments, the hydrolytic degradation of CTFE is neither measurable nor expected. In fact the substance is a gas at ambient conditions with a strong tendency to partition almost exclusively into the atmosphere.

According to section 2 of REACh Annex XI, testing for hydrolysis may be omitted since it is technically not possible to conduct the study on a volatile gas. Moreover, the Guidance on Information Requirements and Chemical Safety Assessment Chapter R.7a: Endpoint Specific Guidance, Appendix R.7.1-4 indicates that substances with a Henry's Law constant of around 1 hPa m3/mole rapidly volatilise from water. The Henry’s Law constant of CTFE was calculated to be 31.500 Pa m3/mol (HENRYWIN v3.20, EPI Suite v4.0), suggesting that the substance is expected to rapidly volatilise from water to the air.

In any case, although no partition into water is expected, the tendency to hydrolyze has been however 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 CTFE.