2-{4-[4-[4-fluoro-6-(2-(2-vinylsulfonylethoxy)ethylamino)-1,3,5-triazin-2-ylamino]phenylazo]phenylazo}naphthalene-4,6,8-trisulfonate, trisodium salt

Dissociation constant

Link to relevant study record(s)

Reference

Endpoint:

dissociation constant

Type of information:

experimental study

Adequacy of study:

key study

Study period:

07 September 2001

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

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:

Identity: FAT 40'800/A
Batch number: WP 2/01
Aggregate state at room temperature: Solid / powder
Color: Dark orange
Storage conditions: At room temperature at about 20 °C, away form direct sunlight
Expiration Date: February 14, 2007

Dissociating properties:

yes

No.:

#1

pKa:

-7.2

Remarks on result:

other: Arenesulfonic acid (3x), method: Hammett

No.:

#2

pKa:

< 0

Remarks on result:

other: Azobenzene, method: General estimation

No.:

#3

pKa:

0.4

Remarks on result:

other: Secondary Amine, method: Taft

No.:

#4

pKa:

0.6

Remarks on result:

other: Secondary Amine, method: Taft

No.:

#5

pKa:

-1

Remarks on result:

other: Triazine, method: Hammett

No.:

#6

pKa:

-0.4

Remarks on result:

other: Triazine, method: Hammett

No.:

#7

pKa:

-4.3

Remarks on result:

other: Triazine, method: Hammett

The molecular structure of FAT 40'800/A was used for the estimation of the dissociation behaviour. The compound has several sites, which can be protonated.

 

Acid/Base	PKa	Method
Arenesulfonic acid (3 x)*	-7.2	Hammett
Azobenzene **	<0	General estimation
Secondary Amine	0.4	Taft
Secondary Amine	0.6	Taft
Triazine	-1.0	Hammett
Triazine	-0.4	Hammett
Triazine	-4.3	Hammett

 

*The arenesulfonic acids are strong acids. In aqueous solutions they are completely dissociated.

**It is not possible to estimate an exact value for the diazo group, however, protonated azo-benzenes are strong acids and therefore, the azo-group is normally not protonated in aqueous solutions.

The arenesulfonic acids are strong acids. In aqueous solutions they are completely dissociated.

It is not possible to estimate an exact value for the diazogroup, however, protonated azobenzenes are strong acids and therefore, the azo-group is normally not protonated in aqueous solutions.

Conclusions:

The behaviour of the test substance in aqueous solutions is dominated by the strongly acidic -SO3H-groups. Therefore, the molecule is negatively charged and is present in anionic form over the whole environmentally relevant pH range.

Executive summary:

The dissociation constant in water of the test substance was calculated using the Hammett and Taft Correlation methods and seven pKa were estimated. The test substance has dissociating properties because its behavior in aqueous solutions is dominated by the strongly acidic -SO3H-groups. Therefore, the molecule is negatively charged and is present in anionic form over the whole environmentally relevant pH range.

Description of key information

The behaviour of the test substance in aqueous solutions is dominated by the strongly acidic -SO3H-groups. Therefore, the molecule is negatively charged and is present in anionic form over the whole environmentally relevant pH range.

Additional information

The dissociation constant in water of the test substance was calculated using the Hammett and Taft Correlation methods and seven pKa were estimated (RCC 2001). The test substance has dissociating properties because its behavior in aqueous solutions is dominated by the strongly acidic -SO3H-groups. Therefore, the molecule is negatively charged and is present in anionic form over the whole environmentally relevant pH range.