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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Physical & Chemical properties

Dissociation constant

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Reference
Endpoint:
dissociation constant
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
2012
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:
Accepted calculation method
Guideline:
other: REACH guidance on QSARs R.6, May 2008
Principles of method if other than guideline:
ACD 7.0 software program for estimating the dissociation constant (pKa) in water.The recommended method, “apparent constants, approximated”, was used for the estimation. The program was developed by Advanced Chemistry Development Inc.
90 Adelaide Street West, Toronto, Ontario, M5H 3V9, Canada (http://www.acdlabs.com); Copyright © 1994-2003; Build: 18 April 2003
GLP compliance:
no
Dissociating properties:
yes
No.:
#1
pKa:
13 - 16
Temp.:
25 °C
Remarks on result:
other: The dissociation constants for representative constituents of the substance are estimated to be in the range from 13 to 16 for pK1 to pK6 at 25 °C.

1. Defined endpoint: Dissociation constant (pKa) in water

2. Unambiguous algorithm: For the substance the following fragment descriptor (parent compound) was identified as reaction centre: HO-C-R

3. Applicable domain: The identified reaction center has been found as fragment in the Internal Reaction Centers Database with experimental equations. The components considered contain 21 – 173 atoms, which is less than the limit of ACD/pKa DB of 255. The substance has one ionization center with one to six fragments for each components. The substance does not contain the atoms, what are not accepted by ACD/pKa DB. The fragment that occurs in the structure of the substance applied by the program is verified by the user. The rules applied for the substance appears appropriate. An individual uncertainty for the investigated substance is not available.

4. Statistical characteristics: Each calculation from ACD/pKa DB is provided with its 95 % confidence interval and, when available, literature references with experimental results. The accuracy of calculations for simple structures is usually better than ±0.2 pKa units (for complex structures it is better than ±0.5 pKa units).

5. Mechanistic interpretation: The mechanistic basis of the model is the linear free energy relationship (LFER), which is an empirical correlation between the standard free energies of reaction or activation for two series of reactions, both subjected to the same variations in reactant structures or reaction conditions. As applied to the estimation of acid dissociation constants, the LFER is basically a substituent-effect approach.

6. Adequacy of prediction: The results for the substance falls within the applicable domain described above and the estimation rules applied for the substance appears appropriate. Therefore the predicted value can be considered reliable yielding a useful result for further assessment.

Conclusions:
The dissociation constants for representative constituents of the substance are estimated to be in the range from 13 to 16 for pK1 to pK6 at 25 °C.
Executive summary:

The dissociation constants of the substance were estimated by ACD/pKa DB included in ACD/labs 7.00 Release. According to the estimated results, this substance presents mainly as non-ionic form under environmentally relevant pH 5 - 9.

Description of key information

The dissociation constants for representative constituents of the substance are estimated to be in the range from 13 to 16 for pK1 to pK6 at 25 °C.

Key value for chemical safety assessment

pKa at 20°C:
13

Additional information

According to the estimated results, this substance presents mainly as non-ionic form under environmentally relevant pH 5 - 9.