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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:
2008-10-9 to 2010-11-20
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 112 (Dissociation Constants in Water)
Deviations:
no
GLP compliance:
no
Remarks:
ISO 9001 system adopted
Dissociating properties:
yes
pKa:
4.67
Temp.:
20 °C

Table 1. Dissociation constant results at 20 °C for succinic acid

 Sample  Succinic acid (g)  Equivalence Point (mL NaOH)  pKa (=pH at half-equivalence volume)
 1  0.9879 19.77  4.66 
 2  1.0438 20.88  4.67 
 3 0.9887 19.77  4.68 
 Mean    20.14 4.67 
 Fall range      0.01
Conclusions:
The pKa value for succinic acid was determined to be 4.67 at 20 °C, which corresponds to a weak acid.
Executive summary:

In a non-GLP study according to OECD 112 the dissociation constant of succinic anhydride has been determined. The pKa of the test material was determined using the titration method at 20 + 1 °C. All relevant validity criteria were fulfilled. Succinic anhydride is inherently unstable in aqueous media and rapidly hydrolyzes to form succinic acid. The dissociation constant of succinic acid was reported as 4.67 at 20 °C.

Description of key information

In a non-GLP study according to OECD 112 the dissociation constant of succinic anhydride has been determined. Succinic anhydride is inherently unstable in aqueous media and rapidly hydrolyzes to form succinic acid. The dissociation constant of succinic acid was reported as 4.67 at 20 °C.

Key value for chemical safety assessment

pKa at 20°C:
4.67

Additional information

The pKa of the test material was determined using the titration method at 20 + 1 °C. All relevant validity criteria were fulfilled.