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Dissociation constant

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Reference
Endpoint:
dissociation constant
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Remarks:
The IUPAC Data Series are among "reference books containing peer-reviewed physico-chemical data" cited in the ECHA guidance document on information requirements and chemical safety assessment (R.7a).
Qualifier:
no guideline available
Principles of method if other than guideline:
no data
GLP compliance:
not specified
Dissociating properties:
yes
No.:
#1
pKa:
9.23
Temp.:
25 °C
Remarks on result:
other: Acid-base constant: 5.88 * 10E-10
No.:
#2
pKa:
13.05
Temp.:
25 °C
Remarks on result:
other: Acid-base constant: 9.55 * 10E-14
Conclusions:
pKa1 = 9.23 and pKa2 = 13.05
Executive summary:

The peer-reviewed IUPAC Data Series report the following dissociation constants for catechol: pKa1 = 9.23 and pKa2 = 13.05. In the aquatic environment, pH mainly varies from 6 to 8. As a result, at these environmentally relevant pH, catechol should appear under its non-dissociate form.

Description of key information

pKa1 = 9.23 and pKa2 = 13.05

Key value for chemical safety assessment

Additional information

A peer-reviewed document is available and flagged as a key study. Based on the pKa values reported, and knowing the pH of natural aqueous media, catechol should appear under its non-dissociated form at environmentally relevant pH.