Registration Dossier
Registration Dossier
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EC number: 429-750-0 | CAS number: 180898-37-7
Dissociation constant
Administrative data
- Endpoint:
- dissociation constant
- Type of information:
- experimental study
- Adequacy of study:
- supporting study
- Study period:
- 1997-04-03 to 1997-07-23
- Reliability:
- 2 (reliable with restrictions)
Cross-reference
- Reason / purpose for cross-reference:
- reference to same study
Data source
Referenceopen allclose all
- Reference Type:
- study report
- Title:
- Unnamed
- Year:
- 1 997
- Report date:
- 1997
- Reference Type:
- study report
- Title:
- Unnamed
- Year:
- 1 997
- Report date:
- 1997
Materials and methods
Test guideline
- Qualifier:
- no guideline available
- Principles of method if other than guideline:
- The test substance is dissolved in water and potentiometrically titrated with hydrochloric acid. The dissociation constant is determined from the inflection point of the titration curve.
- GLP compliance:
- yes
Test material
- Reference substance name:
- -
- EC Number:
- 429-750-0
- EC Name:
- -
- Cas Number:
- 180898-37-7
- Molecular formula:
- C20H12N4O12S4.2Na
- IUPAC Name:
- disodium dihydrogen 2-[4-(5,7-disulfonato-1H-1,3-benzodiazol-2-yl)phenyl]-1H-1,3-benzodiazole-5,7-disulfonate
- Details on test material:
- - CAS name: 1H-Benzimidazole-4,6-disulfonic acid-2,2´-(1,4-diphenylene) bis, disodium salt
- Molecular formula: C20H12N4O12S4Na2
- Molecular weight: 674g/mol
- physical state: solid
Constituent 1
Results and discussion
Dissociation constantopen allclose all
- No.:
- #1
- pKa:
- 2.5
- Temp.:
- 20 °C
- No.:
- #2
- pKa:
- 3.9
- Temp.:
- 20 °C
Applicant's summary and conclusion
- Conclusions:
- pK1: 2.5 and pK2 3.9 (determined at 20°C)
- Executive summary:
At a pH-value lower than 2.5 not only the carboxylic function is protonated, but also the amino functions. At higher pH-values the amino functions are deprotonated, but the same applies to the carboxylic function.
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