Registration Dossier
Registration Dossier
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EC number: 214-302-7 | CAS number: 1120-24-7
Dissociation constant
Administrative data
Link to relevant study record(s)
- Endpoint:
- dissociation constant
- Type of information:
- calculation (if not (Q)SAR)
- Adequacy of study:
- key study
- Study period:
- 10 February - 20 March 2012
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: Acceptable, well-documented study report, which meets basic scientific principles
- Principles of method if other than guideline:
- The pKa of the test substance was calculated from the molecular structure with commercially available software. An experimental determination of the pKa value is not possible due to the low solubility.
- Dissociating properties:
- yes
- pKa:
- 9.78
- Temp.:
- 25 °C
- Conclusions:
- The pKa is 9.78 ± 0.28 at 25°C for the whole C10 to C18 alkyl range of dimethylalkylamines.
- Executive summary:
Due to the limited solubility of the test substance, the pKa was calculated (ACD/I-Lab Web service software) for C10 alkyl, C12 alkyl, C18 alkyl and C18 alkenyl chain lengths of dimethylalkylamines. The results show that the pKa is independent of chain length for the whole C10 to C18 alkyl range of dimethylalkylamines. The pKa of 9.78 ± 0.28 at 25°C therefore also applies to the test substance.
Reference
For C12 alkyl, C18 alkyl and C18 alkenyl this gave identical results of pKa = 9.78 ± 0.28 at 25°C and zero ionic strength. For C10 alkyl, the result was pKa = 9.79 ± 0.28. This difference of 0.01 pKa units is not significant, so that the pKa can be considered independent of chain length for the whole C10 to C18 alkyl range of dimethylalkylamines.
Description of key information
Due to the limited solubility of the test substance, the pKa was calculated (ACD/I-Lab Web service software) for C10 alkyl, C12 alkyl, C18 alkyl and C18 alkenyl chain lengths of dimethylalkylamines. The results show that the pKa is independent of chain length for the whole C10 to C18 alkyl range of dimethylalkylamines. The pKa of 9.78 ± 0.28 at 25°C therefore also applies to the test substance.
Key value for chemical safety assessment
- pKa at 20°C:
- 9.78
Additional information
Dissociation of DMA category members
The percentage of neutral (i.e. amine) and protonated forms of DMA category members can be calculated from the pKa of 9.78 (25 °C; identical for all category members)for a given pH using the Henderson-Hasselbach equation.
Percentage of neutral and protonated DMAs at pH 4, 7 and 9
pH |
% amine |
% protonated |
4 |
0.00017% |
99.99983% |
7 |
0.2% |
99.8% |
9 |
14.2% |
85.8% |
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