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Dissociation constant

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Reference
Endpoint:
dissociation constant
Type of information:
calculation (if not (Q)SAR)
Remarks:
estimated by calculation
Adequacy of study:
key study
Study period:
October 30, 1998
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail
Qualifier:
according to guideline
Guideline:
other: Estimation method
GLP compliance:
no
Dissociating properties:
yes
pKa:
>= -7.4 - <= 7.2
Remarks on result:
other: Temperature not specified
Conclusions:
pKa of FAT 40571/A is >= -7.4 to 7.2
Executive summary:

Calculation of the Dissociation Constants of FAT 40'571/A revealed that t he molecule is negatively charged and is present in anionic form over the whole environmentally relevant pH range. The primary amine is protonated in the strong acidic range of pH (pka = 2.0). However, the behaviour of the test substance in aqueous solutions is dominated by the strongly acidic -S03H groups and the alkylsulfuric acid group. Additionally, the hydroxy group in the alpha-naphthol is

dissociated in the neutral and alkalic range pH

Description of key information

pKa of Reactive Brown 49 is >= -7.4 to 7.2

Key value for chemical safety assessment

pKa at 20°C:
-7.4

Additional information

Calculation of the Dissociation Constants of FAT 40'571/A revealed that t he molecule is negatively charged and is present in anionic form over the whole environmentally relevant pH range. The primary amine is protonated in the strong acidic range of pH (pka = 2.0). However, the behaviour of the test substance in aqueous solutions is dominated by the strongly acidic -S03H groups and the alkylsulfuric acid group. Additionally, the hydroxy group in the alpha-naphthol is dissociated in the neutral and alkalic range pH.

Based on the calculation pKa of FAT 40571/A 49 is >= -7.4 to 7.2