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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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

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Reference
Endpoint:
dissociation constant
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Remarks:
The study was conducted in accordance with OECD 112 but full details are not available.
Qualifier:
according to guideline
Guideline:
OECD Guideline 112 (Dissociation Constants in Water)
Deviations:
not specified
GLP compliance:
not specified
Dissociating properties:
yes
No.:
#1
pKa:
< 2
Remarks on result:
other: temperature not available
No.:
#2
pKa:
< 2
Remarks on result:
other: temperature not available
No.:
#4
pKa:
3.28
Remarks on result:
other: temperature not available
No.:
#5
pKa:
5.27
Remarks on result:
other: temperature not available
No.:
#6
pKa:
6.99
Remarks on result:
other: temperature not available
No.:
#8
pKa:
12.09
Remarks on result:
other: temperature not available

ATMP-N-oxide was determined to have six pKa values

pKa 1 = <2

pKa 2 = <2

pKa 3 = 3.28

pKa 4 =5.27

pKa 5 =6.99

pKa 6 = 12.09


Conclusions:
The substance was determined to have six dissociation constant using a relevant test method. The result is considered reliable.

Description of key information

Dissociation constant (ATMP-N-oxide-xK): ATMP-N-oxide acid has six ionisable phosphonate groups.

Key value for chemical safety assessment

Additional information

In aqueous solution, ATMP-N-Oxide-5K will ionise in aqueous solution to form ATMP-N-oxide acid and potassium ion. Six dissociation constant listed below were obtained for the potassium salt of ATMP-N-Oxide using OECD 112. The result is considered reliable and is selected as key study.

pKa1 = <2

pKa2 = <2

pKa3 = 3.28

pKa4 = 5.27

pKa5 = 6.99

pKa6 = 12.09

Also, six dissociation constants as listed below were obtained for the parent acid (ATMP-N-Oxide) at 25°C using potentiometric titration method. ATMP-N-Oxide was found to titrate as a pentabasic acids with two strongly dissociated protons and one very weakly acidic proton.

pKa1 = <2

pKa2 = <2

pKa3 = 3.28

pKa4 = 5.26

pKa5 = 6.95

pKa6 = 12.05

Similarly, ATMP-N-oxide was predicted to have six ionisable groups as listed below.


pKa 1 = 1.3
pKa 2 = 2.7
pKa 3 = 4.2
pKa 4 = 5.9

pKa 5 = 7.3

pKa 6 = >10

An approximate experimental determination, using stoichiometric 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 is reported in section 4.20.