(3-chloropropyl)triethoxysilane

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2008-07-23 to 2009-05-25

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Version / remarks:

27 July 1995

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Version / remarks:

December 1992

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Key result

Water solubility:

ca. 113 mg/L

Temp.:

20 °C

pH:

4.7

Remarks on result:

other: after 2 hours

Details on results:

The test substance showed a rapid hydrolysis, therefore a simplified flash test was used.

Because of the low stability of the test item in water the expression “greater than or equal to” was used for the result of the water solubility in the test report.

The saturation concentration of (3-chloropropyl)triethoxysilane at room temperature was estimated by a simplified flask method. The pH of the solution was 4.7.

After mixing about 0.13 g of test item with 5 mL of water, the test item was floating as globules in the water. After centrifugation the aqueous phase was diluted with acetone. The determination of the concentration in the above mentioned solution was performed by GC with respect to a calibration curve.

Due to the low stability of (3-chloropropyl)triethoxysilane in water, the water solubility of (3-chloropropyl)triethoxysilane at room temperature could only be roughly estimated by a simplified flask method and was found to be =113 mg/L (after 2 hours). Because of the low stability of the test item in water the expression “greater than or equal to” was used for the result of the water solubility.

An example of calibration data for test item-standards is given in Table 2. The r² fit was 0.9994 (optimum 1.0000). This reflects the linearity of the GC-system within the calibration range of 4.918 µg/mL to 73.77 µg/mL of the test item.

Table 1: Results of the water solubility of (3-chloropropyl)triethoxysilane

Initial weight of test item [g]	Water added [mL]	Measured concentration [mg/L]	Dilution Factor	Solubility in water [mg/L]	Mean [mg/L]
0.14	5	37.599	3	112.796	113.08
0.13	5	37.790	3	113.371

Table 2 Calibration Data of (3-chloropropyl)triethoxysilane

Concentration [µg/mL] (X)	Peak Area (Y)	Deviation (%)
4.918	27.59553	11.6
9.836	55.03376	1.3
13.7704	74.74595	-4.3
19.672	115.84454	1.1
24.59	144.7618	0.0
36.885	213.92059	-2.7
49.18	298.84586	1.1
73.77	447.12851	0.2

 

Conclusions:

A water solubility value of approximately 113 mg/L at pH 4.7 and. 20°C was measured in a reliable study conducted according to OECD Guideline 105, and in compliance with GLP. Only the preliminary test was carried out as the substance is hydrolytically unstable; the measured value can only be considered approximate for this reason.

Description of key information

Water solubility [(3-chloropropyl)triethoxysilane]: approximately 113 mg/L at 20 and pH 4.7 (OECD 105)

Water solubility [(3-chloropropyl)silanetriol]: Above approximately 1000 mg/L condensation reactions can occur over time, limiting the concentration dissolved in water. The calculated solubility is 1.0E+06 mg/L (QSAR)

Water Solubility [ethanol]: miscible with water

Key value for chemical safety assessment

Water solubility:

113 mg/L

at the temperature of:

20 °C

Additional information

A measured water solubility value of approximately 113 mg/L at 20 and pH 4.7 was determined for the submission substance using a simplified flask method in accordance with OECD Test Guideline 105 and in compliance with GLP. Due to the hydrolytic instability of the substance in water, a shorter equilibration time of 2 hours and lower initial amount of the substance was used. The result is considered to be reliable to give an indication of the expected water solubility of the substance and is thus selected as key study.

In contact with water, the submission substance hydrolyses moderately rapidly to form (3-chloropropyl)silanetriol and ethanol.

The silanol hydrolysis product, (3-chloropropyl)silanetriol, 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 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 equilibrium towards the tetramer. At loadings below 500 mg/L of (3-chloropropyl)silanetriol, 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.

The hydrolysis product, (3-chloropropyl)silanetriol, is very hydrophilic and hence the calculated solubility is 1.0E+06 mg/L 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 reaction 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 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 JA 1986).

 

References:

PFA (2016am). Peter Fisk Associates, Analogue Report - Silanols and aquatic systems. Reference:404.105.003

 

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. New York,NY: Wiley-Interscience. 2:PP.1325 1986.