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Physical & Chemical properties

Dissociation constant

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Reference
Endpoint:
dissociation constant
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
key study
Study period:
September 3, 2015
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 112 (Dissociation Constants in Water)
Principles of method if other than guideline:
The pKa values have been estimated based on known or calculated data for a number of relevant substructures.
Specific details on test material used for the study:
It is difficult to measure the pKa of all of the individual protons experimentally, therefore a structural assessment has been performed in order to generate the necessary information.
Dissociating properties:
yes
pKa:
> 0.5 - < 15
Temp.:
25 °C
Remarks on result:
other:
Remarks:
An experiment is not conducted due to the difficulty of the experiment.
Conclusions:
According to the pKa values have been estimated based on known or calculated data for a number of relevant substructures, the pKa values of the labile protons in Everzol Red CDN span a range from approximately 0.5 to 15.
Executive summary:

This test using the procedures outlined in the REACH Centre Study Plan for TRC 150309-1.

Everzol Red CDN is a reactive disazo dye in which there are a number of labile protons. It is difficult to measure the pKa of all of the individual protons experimentally, therefore a structural assessment has been performed in order to generate the necessary information. The pKa values have been estimated based on known or calculated data for a number of relevant substructures. Therefore, the pKa values of the labile protons in Everzol Red CDN span a range from approximately 0.5 to 15. The two sulphonic acid groups dictate the solubility behaviour of Red CDN. The dye would be expected to be highly soluble in water across the full pH range and only under very acidic conditions (pH <1) would solubility be compromised. In addition to the sulphonic acids groups, Red CDN also benefits from the solubilising effects of the sulphate group (which makes an important contribution at lower pH) and the nicotinic acid group.

Description of key information

According to the pKa values have been estimated based on known or calculated data for a number of relevant substructures, the pKa values of the labile protons in Everzol Red CDN span a range from approximately 0.5 to 15.

Key value for chemical safety assessment

Additional information

Everzol Red CDN is a reactive disazo dye in which there are a number of labile protons. It is difficult to measure the pKa of all of the individual protons experimentally, therefore a structural assessment has been performed in order to generate the necessary information. The pKa values have been estimated based on known or calculated data for a number of relevant substructures. Therefore, the pKa values of the labile protons in Everzol Red CDN span a range from approximately 0.5 to 15. The two sulphonic acid groups dictate the solubility behaviour of Red CDN. The dye would be expected to be highly soluble in water across the full pH range and only under very acidic conditions (pH <1) would solubility be compromised. In addition to the sulphonic acids groups, Red CDN also benefits from the solubilising effects of the sulphate group (which makes an important contribution at lower pH) and the nicotinic acid group.