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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:
16 Nov 2001 to 4 Oct 2002
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
equivalent or similar to guideline
Guideline:
EPA OPPTS 830.7370 (Dissociation constants in water)
Deviations:
not specified
GLP compliance:
not specified
Dissociating properties:
yes
No.:
#1
pKa:
9.59
Temp.:
25 °C

pKa Value - Results

Titration data sets of pH against volume of titrant were manipulated electronically using pKaLOGP v5.1. Six apparent pKa values in the presence of co-solvent were evaluated. Using the same software a “Multi-set” of the six data sets was formed and a Yasuda-Shedlovsky extrapolation performed to calculate the pKa value at zero percent organic content. Two of the six points were excluded from the Yasuda- Shedlovsky plot due to their poor fit with the line. The pKa was evaluated to be 9.59.

 

Description of key information

pKa is 9.59 at 25 ºC (OPPTS 830.7370).

Key value for chemical safety assessment

Additional information

Due to low water solubility of the test substance the titrations were performed using varying amounts of co-solvent methanol. The result was calculated by extrapolation to zero-organic content using the Yasuda-Shedlovsky theorem.

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