Registration Dossier

Physical & Chemical properties

Dissociation constant

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
dissociation constant
Data waiving:
study technically not feasible
Justification for data waiving:
other:
Justification for type of information:
Annex IX for REACH requires that a dissociation constant be measured for the sample dissolved in water. OECD – 112 is the method listed for this endpoint; it can be performed three ways: titration method / spectrophotometric method / conductometric method. There are some general caveats listed in OECD-112, however what constitutes “low solubility” is not defined.
1. The titration method is not suitable for low solubility compounds

2. The spectrophotometric method suitability is as follows:
a. not applicable to compounds having appreciably different UV.VIS-absorption spectra for the dissociated and undissociated forms.
b. may be suitable for low solubility compounds
c. may be suitable for non-acid/base dissociations (eg complex formation)

3. In cases where the Onsager equation holds, the conductometric method may be used
a. even at moderately low concentrations
b. even in cases for non-acid/base equilibria


This substance is a complex mixture of esters and amides. None of the main constituents dissociate when dissolved in water so no dissociation constant can be measured (scientifically unjustified). A minor amount of unreacted test substance is present in the product. The constituents present in this acid are reported to have a pKa of between 4.59 to 4.80.
Conclusions:
This substance is a complex mixture of esters and amides. None of the main constituents dissociate when dissolved in water so no dissociation constant can be measured (scientifically unjustified). A minor amount of unreacted test substance is present in the product. The constituents present in this acid are reported to have a pKa of between 4.59 to 4.80.

Description of key information

Annex IX for REACH requires that a dissociation constant be measured for the sample dissolved in water. OECD – 112 is the method listed for this endpoint; it can be performed three ways: titration method / spectrophotometric method / conductometric method. There are some general caveats listed in OECD-112, however what constitutes “low solubility” is not defined.

1.The titration method is not suitable for low solubility compounds

2.The spectrophotometric method suitability is as follows:

a.not applicable to compounds having appreciably different UV.VIS-absorption spectra for the dissociated and undissociated forms.

b.may be suitable for low solubility compounds c.may be suitable for non-acid/base dissociations (eg complex formation)

3.In cases where the Onsager equation holds, the conductometric method may be used

a.even at moderately low concentrations

b.even in cases for non-acid/base equilibria

This substance is a complex mixture of esters and amides. None of the main constituents dissociate when dissolved in water so no dissociation constant can be measured (scientifically unjustified). A minor amount of unreacted test substance is present in the product. The constituents present in this acid are reported to have a pKa of between 4.59 to 4.80.

Key value for chemical safety assessment

pKa at 20°C:
4.7

Additional information