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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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

Environmental fate & pathways


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Administrative data

Link to relevant study record(s)

Data waiving:
study technically not feasible
Justification for data waiving:
the study does not need to be conducted because the substance is highly insoluble in water

Description of key information

Hydrolysis: endpoint waived due to the substance being very highly insoluble in water.

Key value for chemical safety assessment

Additional information

The requirement to conduct a hydrolysis study was waived in accordance with Column 2 of REACH Annex VIII because the substance is highly insoluble in water. Octaphenylcyclotetrasiloxane has a predicted water solubility value of <1E-05 mg/l at 20°C.

Cyclic siloxanes such as octaphenylcyclotetrasiloxane can undergo hydrolysis reactions in water, resulting in breaking of the Si-O bonds. The first step is ring-opening to give a linear siloxanediol (octaphenyltetrasiloxanediol for the present substance). This intermediate then undergoes chain-shortening reactions to give the final silanediol product. For octaphenylcyclotetrasiloxane, the overall reaction is as follows:

[-Si(C6H5)2O-]4+ 4H2O → 4(C6H5)2Si(OH)2

The final product is diphenylsilanediol.

However, due to the extremely low water solubility of the substance, hydrolysis is not expected to be a significant removal process.