Carboxylic acid pfCa table

The general structure of perfluorocarboxylic acids is F(CF2) cCOOH. Generally, PFCAs consist of 6 to 16 carbon atoms, where x = 5 to 15 (Table 3.1). Within this group of PFCAs, the most common is perfluorooctane carboxylic acid (PFOA, 8 carbon atoms). It should be noted, however, that trifluoroacetic acid (TFA, 1 carbon atom) is also a common and well-studied PFCA [2,3]. Similar to the PFSAs, the PFCAs also have small pAa values, typically 2-3 [4, 5] and are dissociated at environmental pH values ... 

A list of Ka values for various carboxylic acids is given in Table 20.3. For most, Ka is approximately 10 to 10 . Acetic acid, for instance, has Kg = 1.75 X 10 at 25 "C, which corresponds to a pfCa of 4.76. In practical terms, a Ka value near 10 means that only about 0.1% of the molecules in a 0.1 M solution are dissociated, as opposed to the 100% dissociation foimd with strong mineral acids like HCl. 

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