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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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

Description of key information

The pKa value for 4-Hydroxy-TEMPO was calculated as 5.07.

Key value for chemical safety assessment

pKa at 20°C:

Additional information

The dissociation constant of 4-Hydroxy-TEMPO is determined by QSAR estimation with the programme SPARC v.4.6 that is recommended in the REACH Guidance on information requirements and chemical safety assessment, Chapter R., Table R.7.1-36, thus the calculated value is reliable with restrictions. Therfore SPARC software v4.6 ( developed at the University of Georgia through grants from USEPA) was used. The supporting study reports a dissociation constant of 5.9. A pka value of 5.07 was predicted by the QSAR model. The differences between the theoretical and the practial value can be explained by the structure and the temperature.