Registration Dossier

Administrative data

Endpoint:
dissociation constant
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
Guideline study performed 2017 at GLP accredited laboratory
however, due to the nature of the substance, distinct pKa values could not be determined

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017
Report Date:
2017

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 112 (Dissociation Constants in Water)
Principles of method if other than guideline:
Titration with KOH
GLP compliance:
no
Remarks:
GLP facilities, but conducted as non-GLP

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
liquid
Details on test material:
Commercial grade containing approximately 45% actives
Specific details on test material used for the study:
Batch PAH 330/132/1A
Commercial grade material in water

Results and discussion

Dissociating properties:
yes
Dissociation constantopen allclose all
No.:
#1
pKa:
ca. 6.2
Temp.:
23 °C
No.:
#2
pKa:
ca. 8
Temp.:
23 °C

Any other information on results incl. tables

The normal pH of the material is 6.2

The reported pKa for triethanolamine is 6.2

Applicant's summary and conclusion

Conclusions:
The substance is a salt of tertiary amine and a weak organic acid and will be dissociated under normal biological and environmental conditions.
The pKa measured is comparible to that of the amine and is at the measure pH of 6.2.
The dissociation of the salt means that for environmental and toxicological assessment, the substance will have comparible propteries to the triethanolamine and dodecenylsuccinic acid starting materials.
1 At pH 1 (stomach pH), we would suggest that the acid would exist as the free acid and the triethanolamine as the protonated amine cation.
2 At pH 6 – 8 (environmental pH), we would suggest that the acid would exist in its fully ionised form and the triethanolamine as the protonated amine cation, however the extent of ionisation would be pH dependent.
3 At pH > 8, we would suggest that the acid would exist in its fully ionised form, as a salt, the nature of which would be determined by the environmental condition and the triethanolamine as the free amine however the extent of ionisation would be pH dependent.
Executive summary:

From literature references, we would suggest that the pKa value of 7.97 probably relates to the triethanolamine undergoing conversion from the pronated NH (Structure 1) to the free amine N (Structure 2).

 

The pKa value of 6.17 therefore probably relates to thedoubly deprotonated dodecenyl succinic carboxy anion (Structure 3), undergoing conversion to the mono protonated dodencenyl succininc carboxy anion with the expectation that a mono protonated dodecenyl succinic carboxy anion (Structure 4) would be formed from the free acid (Structure 5) with a lower pKa. Structures of the species detailed are given below: