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Dissociation constant

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Description of key information

Key result for PFPA (degradation product), CAS# 422-64-0:

Dissociation constant: 0.34 (pH titration and electric conductivity methods)

Key value for chemical safety assessment

Additional information

Discussion for PFPA (degradation product), CAS# 422-64-0:

The acidity constants for PFPA and a range of perfluoroalkanoic acids with 1 to 5 carbon atoms in the alkyl chain were determined by pH titration and by electric conductivity (Moroi et al. 2001, Bull. Chem. Soc. Japan 74:667-273).  An analytical procedure for titration and conductivity yielded a pKa for titration 1 of 0.38 ± 0.01, a pKa for titration 2 of 0.34 ± 0.04, and a pKa for conductivity of 0.29 ± 0.03.  The average pKa of these results was 0.34.  This study is classified as reliable with restrictions.  While the study itself is robust and has been determined to be valid, it was not done under GLP.  Also, the study did not follow a standard method, such as OECD TG112.  That said, the experimental result for pKa is relevant to the determination of this parameter because the methodology is very similar to the standard method of pKa determination.