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Physical & Chemical properties

Dissociation constant

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Endpoint:
dissociation constant
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Justification for type of information:
QSAR prediction: migrated from IUCLID 5.6
Guideline:
other: REACH guidance on QSARs R.6,May/June 2008
Principles of method if other than guideline:
general method for pKa
Dissociating properties:
yes
No.:
#1
pKa:
ca. 10.6
Temp.:
25 °C
No.:
#2
pKa:
ca. 10.3
Temp.:
25 °C
No.:
#3
pKa:
ca. 10.3
Temp.:
25 °C
No.:
#4
pKa:
ca. 10.2
Temp.:
25 °C

The calculation has been run by SPARK On-line calculator :

Current implementations (selected references):

  Major reference:Hilal, Said, S. W. Karickhoff and L. A. Carreira,

       "A Rigorous Test for SPARC's Chemical Reactivity Models: Estimation of

        More Than 4300 Ionization pKa's,"  Quant. Struc. Act. Rel., 14, 348 1995.

Conclusions:
pKa values are 10.6, 10.3, 10.3 and 10.2
Endpoint:
dissociation constant
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Justification for type of information:
QSAR prediction: migrated from IUCLID 5.6
Principles of method if other than guideline:
ACD Tox Suit 2.95
Dissociating properties:
yes
No.:
#1
pKa:
ca. 11.7
Temp.:
25 °C
No.:
#2
pKa:
ca. 10
Temp.:
25 °C
No.:
#3
pKa:
ca. 8.9
Temp.:
25 °C
No.:
#4
pKa:
ca. 7
Temp.:
25 °C
Conclusions:
The pKa values are 11.7, 10.0. 8.9 and 7.0 according to predictions

Description of key information

Predictions of the dissociation constant are made by SPARC and ACD Tox Suite 2.95. .
pKa values are 10.6, 10.3, 10.3 and 10.2 ( according to SPARC). pKa values are 11.7, 10.0, 8.9 and 7 (according to ACD Tox Suite 2.95). These values were compared to literature values of the corresponding diamine and are in the same range.(10.6 and 8.6).

Key value for chemical safety assessment

pKa at 20°C:
10

Additional information

It is very hard to distinguish the different dissociations constants, pKa, in i.e titration ( OECD Guideline 112) because they will all enter in the same peak. Therefore a prediction was done by SPARC and ACD Tox Suite 2.95. These values were compared to literature values.