Registration Dossier
Registration Dossier
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EC number: 201-180-5 | CAS number: 79-14-1
Dissociation constant
Administrative data
Link to relevant study record(s)
- Endpoint:
- dissociation constant
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 13 January 2021 - 18 August 2021
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 112 (Dissociation Constants in Water)
- GLP compliance:
- yes (incl. QA statement)
- Dissociating properties:
- yes
- No.:
- #3
- pKa:
- 3.85
- Temp.:
- 20 °C
- No.:
- #2
- pKa:
- 3.7
- Temp.:
- 20 °C
- No.:
- #1
- pKa:
- 3.77
- Temp.:
- 20 °C
- Conclusions:
- The overall average pKa for the test substance is 3.77.
- Endpoint:
- dissociation constant
- Type of information:
- experimental study
- Adequacy of study:
- supporting study
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Reason / purpose for cross-reference:
- reference to same study
- Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 112 (Dissociation Constants in Water)
- GLP compliance:
- yes
- Dissociating properties:
- yes
- pKa:
- 3.1
- Temp.:
- 25 °C
- Remarks on result:
- other: mean value: 3.10
- Conclusions:
- The average dissociation constant of glycolic acid at 25°C was 3.10.
- Executive summary:
The average dissociation constant of glycolic acid at 25°C was 3.10.
Referenceopen allclose all
Dissociation Constant (25°C)
Replicate 1 = 3.18
Replicate 2 = 3.05
Replicate 3 = 3.07
Average = 3.10
Description of key information
Glycolic acid has dissociating properties. It will mainly exist as the carboxylate anion (expected 99% ionised at pH > pKa+2) but may exist under both base and acid forms at low pH, in the environmentally relevant range (pH 5-9).
Key value for chemical safety assessment
- pKa at 20°C:
- 3.77
Additional information
The result is consistent with the supporting study, conducted previously on the 70% solution (pKa = 3,10).
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