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Dissociation constant

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Reference
Endpoint:
dissociation constant
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Study completion date - 20 October 2003.
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Qualifier:
no guideline available
Principles of method if other than guideline:
Dissociation constant was calculated by the Hammett and Taft Correlations.
GLP compliance:
no
Specific details on test material used for the study:
Name: FAT 40812/A
Dissociating properties:
yes
No.:
#1
pKa:
11.23
Remarks on result:
other: Hydroxy group
No.:
#2
pKa:
-0.48
Remarks on result:
other: Sulfonic acid group (2x)
No.:
#3
pKa:
-1.45
Remarks on result:
other: Primary amine
No.:
#4
pKa:
-3.9
Remarks on result:
other: Sulfuric acid ester

The hydroxy group of FAT 40812/A is protonated at pH 11.23 and below. All other sites are deprotonated above pH 0. Thus FAT 40812/A will be deprotonated at all sites but the hydroxy group all over the whole environmental relevant pH range (pH 5 to pH 8).

Conclusions:
The test substance will be deprotonated at all sites but the hydroxy group all over the whole environmental relevant pH range (pH 5 to pH 8).
Executive summary:

The dissociation constant in water of the test substance was calculated using the Hammett and Taft Correlation methods and four pKa were estimated. The hydroxy group of the test substance is protonated at pH 11.23 and below. All other sites are deprotonated above pH 0. Thus the test substance will be deprotonated at all sites but the hydroxy group all over the whole environmental relevant pH range (pH 5 to pH 8).


 


The individual pKa values are tabulated as below:


























 Acid/Base



 pKa



 Hydroxy group



 11.23



 Sulfonic acid group (2 x)



 -0.48



 Primary amine



 -1.45



 Sulfuric acid amine



 -3.9


Description of key information

The dissociation constant in water of the test substance was calculated using the Hammett and Taft Correlation methods and four pKa were estimated (RCC 2003). The hydroxy group of the test substance is protonated at pH 11.23 and below. All other sites are deprotonated above pH 0. Thus, the test substance will be deprotonated at all sites but the hydroxy group all over the whole environmental relevant pH range (pH 5 to pH 8).

Key value for chemical safety assessment

Additional information