Registration Dossier
Registration Dossier
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EC number: 209-008-0 | CAS number: 552-30-7
Dissociation constant
Administrative data
Link to relevant study record(s)
Description of key information
Dissociation constants (trimellitic acid): pKa1= 2.91, pKa2= 3.94, pKa3= 5.30 at 20 ± 1 °C.
Key value for chemical safety assessment
- pKa at 20°C:
- 2.91
Additional information
A waiver is proposed for the parent monomer on the basis that trimellitic anhydride hydrolyses almost instantaneously on contact with water and measurement of its dissociation constant(s) is therefore not technically feasible.
Dissociation constants are, however, available for trimellitic acid (TMLA), the hydrolysis product of trimellitic anhydride. At 20 degrees C, the pKa1, pKa2 and pKa3 values of TMLA are 2.91, 3.94 and 5.30, respectively.
The species distribution generated by the dissociation of this acid was determined, according to these constants, as function of pH.
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