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Environmental fate & pathways

Hydrolysis

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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.