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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Physical & Chemical properties

Dissociation constant

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Administrative data

Link to relevant study record(s)

Reference
Endpoint:
dissociation constant
Type of information:
(Q)SAR
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Remarks:
This is an accepted calculation method supported by a limited amount of additional validation.
Justification for type of information:
See attached QMRF/QPRF
Principles of method if other than guideline:
Predictive method
Dissociating properties:
yes
No.:
#1
pKa:
1.3
Remarks on result:
other: 20-25°C
No.:
#2
pKa:
2.7
Remarks on result:
other: 20-25°C
No.:
#3
pKa:
4.2
Remarks on result:
other: 20-25°C
No.:
#4
pKa:
5.7
Remarks on result:
other: 20-25°C
No.:
#5
pKa:
5.9
Remarks on result:
other: 20-25°C
No.:
#6
pKa:
7.3
Remarks on result:
other: 20-25°C
No.:
#7
pKa:
8.8
Remarks on result:
other: 20-25°C
No.:
#8
pKa:
> 10
Remarks on result:
other: 20-25°C

EDTMP was determined to have eight pKa values, of: 
pKa1 = 1.3
pKa2 = 2.7
pKa3 = 4.2
pKa4 = 5.7
pKa5 = 5.9
pKa6 = 7.3

pKa7 = 8.8

pKa8 = >10

Conclusions:
EDTMP acid was determined to have eight dissociation constant using a relevant estimation method.

Description of key information

Dissociation constant (EDTMP-H): EDTMP acid has four phosphonate groups and so eight ionisable protons

Key value for chemical safety assessment

Additional information

Eight dissociation constants as listed below were obtained for the acid using an appropriate estimation method. The result is considered reliable and selected as key study.

pKa1 = 1.3
pKa2 = 2.7
pKa3 = 4.2
pKa4 = 5.7
pKa5 = 5.9
pKa6 = 7.3

pKa7 = 8.8

pKa8 = >10

Also, in a secondary source to which no reliability could be assigned, EDTMP-H has eight dissociation constants as listed below:

1.46 
2.72 
5.05
6.18 
6.63

7.43 
9.22

10.60 


 

An approximate experimental determination, using stocichiometric titration and pH determination of aqueous solutions, has been conducted. This is considered to provide suitable and practical information, which is fit for purpose in the context of REACH chemical safety assessment. This data are reported in Section 4.20.