Reaction mass of 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane and 4,4,14,14-tetraethoxy-3,15-dioxa-8,9,10-trithia-4,14-disilaheptadecane

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

GLP compliance:

not specified

Type of method:

other: Turbidity

Key result

Water solubility:

< 1 mg/L

Temp.:

20 °C

Remarks on result:

other: no pH reported

Details on results:

A water solubility value of less than 1 mg/L was determined at 20 ±3 °C.

Table 1: Turbidity result

Flask	concentration Si 69 (mg/L)	Turbidity Units
		1 h	2h	3h
1(A)	119	53	49-53	57
2	26	15	15	17
3	11	6.7	6.8	7
4	3.5	2.6	2.8	3
5	1.2	2.1	2.1	2.2
6(B)	12	5.2	6.6	7.2
7	0.4	0.3	0.4	0.4
8	0.1	0.1	0.2	0.4
9	0	0.1

Conclusions:

A water solubility value of < 1 mg/l for the reaction mass of S2, S3 and S4 was determined at 20 ±3 °C in a reliable study conducted according to generally accepted scientific principles.

Reference 2

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

not stated

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Principles of method if other than guideline:

The water solubility of the test substance was determined by measuring the turbidity of water containing different amounts of the test substance. The procedure is similar to the preliminary test of OECD test guideline 105.

GLP compliance:

no

Type of method:

flask method

Key result

Water solubility:

ca. 1 mg/L

Temp.:

25 °C

Remarks on result:

other: no pH reported

Details on results:

The water solubility of Si 266 at 25±3°C was determined as approximately 1 mg/L.

Table 1: Dependence of turbidity of the test solutions

Flask	Concentration Si 266, mg/l	Turbidity Units
		1h	2h	3h
1(A)	130	118	103	133
2	29	21	21	21
3	12	11.2	11.8	11.3
4	3.8	3.3	3.0	3.0
5	1.3	2.2	1.2	0.9
6(B)	80	64	53
7	2.4	1.5	1.4
8	0.8	0.8	0.9
9	0	0.5		0.8

At a concentration of approx. 1 mg/l the turbidity of the Si266- solutions disappears. A decrease in turbidity with time in some samples was observed. No further measurements at longer equilibration times were performed due to the unknown stability of the test substance to hydrolysis.

Conclusions:

The test for S2 was conducted similar to the preliminary test of OECD test guideline 105. An approximate value of 1 mg/L for the water solubility was determined.

Reference 3

Endpoint:

water solubility

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

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:

Please refer to the attached QM(P)RF documents

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:

0.014 mg/L

Temp.:

20 °C

pH:

7

Remarks on result:

other: S2

Key result

Water solubility:

0.012 mg/L

Temp.:

20 °C

pH:

7

Remarks on result:

other: S3

Details on results:

The water solubility has been calculated for each component of the multiconstituent substance. The results are as follows:
4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane, S2, 56706-10-6: 0.014 mg/l
4,4,14,14-tetraethoxy-3,15-dioxa-8,9,10-trithia-4,14-disilaheptadecane, S3: 0.012 mg/l
4,4,15,15-tetraethoxy-3,16-dioxa-8,9,10,11-tetrathia-4,15-disilaoctadecane, S4: 0.0032 mg/l

Conclusions:

Water solubility values of 0.012-0.014 mg/L were obtained for the components of the substance using an accepted calculation method. The results are considered to be reliable.

Description of key information

Water solubility (components of the substance): <1 mg/l at 20-25°C (WoE)

Water solubility (silanol hydrolysis products): 1E+06 mg/l (QSAR); the concentration dissolved in water is limited to about 1000 mg/l by condensation reactions

Water Solubility [ethanol]: miscible at 20°C

Key value for chemical safety assessment

Water solubility:

0.01 mg/L

at the temperature of:

20 °C

Additional information

No measured data are available for the water solubility of the registered substance.

A water solubility value of approximately 1 mg/l for the S2 constituent (CAS 56706-10-6) was determined in a study similar to the preliminary test described in OECD Test Guideline 105 (4.8.159 Holldorff H 1997). The study is limited by the shortened time-scale and the fact that only the preliminary test was carried out. Further testing was not carried out because the substance was suspected to be hydrolytically unstable but the half-life was not known.

A water solubility value of <1 mg/l was determined for the reaction mass of S2, S3 and S4 in a study that is considered to be reliable (4.8.158 Holldorff H 1998).

In addition, the registered substance is a multiconstituent substance containing trialkoxysilanes [reaction mass of 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane (S2) and 4,4,14,14-tetraethoxy-3,15-dioxa-8,9,10-trithia-4,14-disilaheptadecane (S3)]; predicted water solubilities of 0.014 mg/l and 0.012 mg/l at 20°C were determined for S2 and S3 constituents of the substance respectively. The available results are considered to be reliable and used as weight of evidence that the water solubility of the substance is <1 mg/l.

The silanol hydrolysis products of S2 and S3 (3-{[3-(trihydroxysilyl)propyl]disulfanyl}propyl)silanetriol and (3-{[3-(trihydroxysilyl)propyl]trisulfanyl}propyl)silanetriol, may undergo condensation reactions in solution to give siloxane dimers, linear and cyclic oligomers and highly cross-linked polymeric particles (sol) that may overtime 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.

In general, for very hydrophilic silanols such as these, the soluble monomer is expected to predominate in solution (>99%) at loadings below 500 mg/l of the silanol hydrolysis products (silanetriols), 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. However, no measured data are available relating to substances containing two silanetriol groups and it is possible that condensation would occur at lower levels for these substances.

The hydrolysis products are very hydrophilic and hence the calculated solubility for each hydrolysis product 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 or 1000 g/l is indicative but has no practical meaning. The prediction is however considered valid for use in calculation of 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 JA 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).