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Water solubility

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Water solubility [3-[3-(triethoxysilyl)propyl]oxolane-2,5-dione]: not relevant
Water Solubility [2-[3-(triethoxysilyl)propyl]butanedioic acid]: 530 mg/l at 20°C (QSAR)
Water Solubility [2-[3-(trihydroxysilyl)propyl]butanedioic acid]: condensation reactions can occur over time, limiting the concentration dissolved in water or aqueous media. The calculated solubility is 1E+06 mg/l (QSAR)
Water solubility [ethanol]: Miscible at 20°C

Key value for chemical safety assessment

Additional information

The requirement to conduct a water solubility study for the substance is waived on the basis that the substance hydrolyses very rapidly in contact with water to form an intermediate hydrolysis product, 2-[3-(triethoxysilyl)propyl]butanedioic acid; the ultimate hydrolysis products are 2-[3-(trihydroxysilyl)propyl]butanedioic acid and ethanol.

It is expected that the butanedioic acid group present in both the intermediate and ultimate hydrolysis products would complex with the calcium or other metals present in test media (and potentially in some environmental waters) to form an insoluble salt which precipitates out of solution. This statement is consistent with findings in solubility trials performed in association with REACH-required ecotoxicity studies (Daphnia and algae acute toxicity studies; WIL 2015). In these studies, precipitates were observed at concentrations as low as 1 mg/l. Other cross-reactions or self-reactions between the carboxylic acid and the silanol groups may also be possible.

The water solubility of the intermediate hydrolysis product, 2-[3-(triethoxysilyl)propyl]butanedioic acid has been calculated using a validated QSAR method to be 530 mg/l at 20°C.

The ultimate hydrolysis product, 2-[3-(trihydroxysilyl)propyl]butanedioic acid is very hydrophilic and hence the calculated solubility is 1E+06 mg/l at 20-25°C using a QSAR method. This QSAR method for water solubility cannot be validated for silanetriols because the saturation concentration of silanetriols in water is limited by condensation reactions rather than lack of true solubility, as discussed above. A prediction of 1E+06 mg/l is indicative but has no practical meaning. The prediction is however considered valid for use in calculation of the Henry’s Law Constant and for environmental exposure modelling and toxicokinetics modelling because it is considered to adequately describe the hydrophilicity of the substance and hence the partitioning behaviour.

 

Ethanol is miscible with water (Riddick 1986).

Riddick J. A (1986). Riddick, J. A.; Bunger,W.B.; Sakano,T.K.; Organic Solvents: Physical Properties and Methods of Purification. Techniques of Chemistry. 4th ed: Wiley-Interscience. 2:pp.1325 1986