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Dissociation constant

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Description of key information

Key result for CAS# 297730-93-9:
Substance does not contain ionizable groups.
Key result for PFBA (degradation product), CAS# 375-22-4:
pKa at 25 °C: 0.40 (geometric mean of conductimetric and titrimetric methods, equivalent to OECD TG112).

Key value for chemical safety assessment

Additional information

Discussion for CAS# 297730-93-9:

We have proposed waiving of testing of dissociation constant for CAS# 297730-93-9 due to lack of ionizable groups.

Discussion for PFBA (degradation product), CAS# 375-22-4:

The dissociation constant of PFBA at 25 °C was determined by several methods. The key study used a mixture of titrimetric and conductimetric methods which are equivalent to OECD TG112. The study was well documented and appears well-performed. Several supporting studies were available using potentiometric, 19F/1H NMR, and an unknown method to establish extent of dissociation. Measurements of pKa ranged from 1.74 (method unknown) at 25 °C to -0.04 at 35 °C (NMR method). PFBA is a strong acid that will be completely deprotonated in aquatic systems. The key study was chosen based on best documentation and the equivalent to OECD test guidelines.