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EC number: 203-542-8 | CAS number: 108-01-0
Dissociation constant
Administrative data
Link to relevant study record(s)
- Endpoint:
- dissociation constant
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: well documented publication which meets basic scientific principles
- Qualifier:
- no guideline followed
- Principles of method if other than guideline:
- The pKa values of the conjugate acids of alkanolamines (MDEA, DMMEA (= Dimethylaminoethanol), DEEA, DEMEA, AMP, MMEA, DIPMEA and TBAE) were determined by potentiometric titration.
- GLP compliance:
- not specified
- Dissociating properties:
- yes
- No.:
- #1
- pKa:
- 9.23
- Temp.:
- 20 °C
- No.:
- #2
- pKa:
- 8.99
- Temp.:
- 30 °C
- No.:
- #3
- pKa:
- 8.69
- Temp.:
- 45 °C
- No.:
- #4
- pKa:
- 8.36
- Temp.:
- 60 °C
- Remarks on result:
- other: Accuracy, +/- 0.03 pKa unit
- Conclusions:
- For dimethylaminoethanol, a pKa value of 9.23 at 20°C was determined.
- Executive summary:
The pKa values of different alkanolamines including dimethylaminoethanol were determined by potentiometric titration (Littel et al., 1990). The pKa values of the samples were calculated from titration data with the use of the SUPERQUAD computer program. The Debye-Hückel equation was additionally applied for conversion of the thermodynamic Kw value and the pKa value in order to take the values of the activity coefficients also into account. The pKa value for dimethylaminoethanol was determined at 20, 30, 45 and 60°C. A pKa value of 9.23 was determined for 20°C.
Reference
All determinations were carried out in triplicate, and the results were reproducible within +/- 0.02 pKa unit. The SUPERQUAD program calculates the accuracy of its results based on the fit of the experimental data to the theoretical equations and the experimental error in the volume of titrant added (+/- 0.02 x 10E-3 L). In almost all cases, this error was +/- 0.02 pKa unit.
Description of key information
Dissociation constant (pKa): 9.23
Key value for chemical safety assessment
- pKa at 20°C:
- 9.23
Additional information
Referring to the key study, a pKa value of 9.23 at 20°C was determined by potentiometric titration (Littel et al., 1990). This value is used for the Chemical Safety Assessment. The supporting study by ESIS (2010) reports a similar pKa value of 9.3 and the second supporting study by Chemservice S.A. (2019) using SPARC v4.6 reports a calculated pKa value of 9.44.
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