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Description of key information

CAS# 756-13-8 cannot be meaningfully examined with respect to adsorption due to rapid hydrolysis.
PFPA (degradation product), CAS# 422-64-0, has an estimated Koc of ca.1 by QSAR (ACDLabs v.12.00)

Key value for chemical safety assessment

Additional information

Under specific conditions, CAS# 756-13-8 may hydrolyze forming perfluoropropionic acid (PFPA, CAS# 422-64-0).  The logarithm of the adsorption coefficient (log Koc) of PFPA was reported from three sources.  The key result was obtained by QSAR simulation ACDLabs v.12.00.  The estimated log Koc at environmentally-relevant pH was -1.06, and the Koc was set at ca.1.  The two remaining estimates were reported in a previous REACh submission for this chemical.  Log Koc obtained using EpiSuite v.3.12, module PCKOC v.1.66 was 1.1.  Log Koc obtained using EUSES, version not reported, was 1.2. 

 

All data were estimated by application of QSAR models.  ACD software models Koc using partition coefficient modified by dissociation constant to correct for ionization of the simulated chemical.  The training set for the partition coefficient module contains perfluoroethyl-, perfluorpropyl- and perfluorobutyl- compounds.  In addition, the software accurately estimates the very low pKa of the test substance.  Therefore, PFPA is within the applicability domain of the model.  The estimates obtained by other models were calculated using unknown or obsolescent versions of the software.  Further, neither model takes dissociation of the strong (pKa = 0.34) acid PFPA into account.  Therefore, the sole reliable estimate of log Koc at environmentally-relevant pH is -1.06, with Koc set at ca.1.