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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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

Link to relevant study record(s)

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.