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Diss Factsheets

Physical & Chemical properties

Water solubility

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Administrative data

Link to relevant study record(s)

Reference
Endpoint:
water solubility
Type of information:
(Q)SAR
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:
See attached QMRF/QPRF
Principles of method if other than guideline:
The result was obtained using an appropriate QSAR method (see attached QMRF and QPRF for details).

The model is an adaptation of the existing SRC model WaterNT v 1.01, aka WaterFrag, which is a component of the EPI Suite. This model is based on fragment values. That is, the chemical structure is broken down into its constituent functional groups, and the contribution of each group toward the overall solubility is calculated. Certain correction factors may also apply. Whilst this method is good in principle, it suffers from not having reliable fragment values for substances containing Si-O bonds. Therefore, multiple linear regression on a set of organosilicon compounds has been used to generate new fragment values for silicon and oxygen bound to silicon (with separate values for –OH and other oxygen). The adapted model applies to substances containing Si-O bonds.
Key result
Water solubility:
63 mg/L
Temp.:
20 °C
pH:
7
Conclusions:
A water solubility value of 63 mg/l at 20°C was obtained for the substance using a validated QSAR. The result is considered to be reliable.

Description of key information

Water solubility [3-(triethoxysilyl)propyl methacrylate]: 63 mg/l at 20°C (QSAR)

Water solubility [3-(trihydroxysilyl)propyl methacrylate]: the concentration dissolved in water is limited to about 1000 mg/l by condensation reactions, predicted water solubility is 1.0E+06 mg/l (QSAR)

Water Solubility [ethanol]: miscible at 20°C

Key value for chemical safety assessment

Water solubility:
63 mg/L
at the temperature of:
20 °C

Additional information

The water solubility of the parent substance, 3-(triethoxysilyl)propyl methacrylate has been predicted to be 63 mg/l at 20°C using a validated QSAR estimation method. The result is considered to be reliable.

In contact with water, 3-(triethoxysilyl)propyl methacrylate hydrolyses moderately to form 3-(trihydroxysilyl)propyl methacrylate and ethanol.

The silanol hydrolysis product, 3-(trihydroxysilyl)propyl methacrylate, may undergo condensation reactions in solution to give siloxane dimers, linear and cyclic oligomers and highly cross-linked polymeric particles (sol) that may over time form an insoluble gel and a dynamic equilibrium is established. The overall rate and extent of condensation is dependent on nominal loading, temperature, and pH of the system, as well as what else is present in the solution.

The condensation reactions of silanetriols may be modelled as an equilibrium between monomer, dimer, trimer and tetramer, with the linear tetramer cyclising to the thermodynamically stable cyclic tetramer. At higher loadings, cross-linking reactions may occur. The reactions are reversible unless the cyclic tetramer concentration exceeds its solubility; in this case, the cyclic tetramer forms a separate phase, driving the equilibrium towards the tetramer. At loadings below 500 mg/l, 3-(trihydroxysilyl)propyl methacrylate, the soluble monomer is expected to predominate in solution (>99%), with small amounts of dimer and oligomers. Condensation reactions are expected to become important at loadings above about 1000 mg/l causing the formation of insoluble polymeric particles (sols) and gels over time. Further information is given in a supporting report (PFA 2016am) attached in Section 13 of IUCLID.

The silanol hydrolysis product is very hydrophilic and hence the calculated solubility is 1E+06 mg/l at 20°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 the 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 J. A 1986).

References:

 

PFA (2016am). Peter Fisk Associates, Silanols and aquatic systems, 404.105.003

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