Tri(isopropoxy)vinylsilane

Biodegradation in water: screening tests

Description of key information

Biodegradation in water (screening tests): 89% in 28 days (EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test)), read across from an analogous substance. No significant biodegradation of the silanol hydrolysis product, vinylsilanetriol, is expected.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

There are no reliable ready biodegradation data available for tri(isopropoxy)(vinyl)silane, therefore good quality data for the analogous substance, tris(2-methoxyethoxy)vinylsilane (CAS 1067-53-4) have been read across. Both substances hydrolyse at a moderate to rapid rate and extensive or complete hydrolysis in the course of the 28-day ready biodegradation study ist o be expected, and share the same silanol hydrolysis product, vinylsilanetriol. The other hydrolysis products are isopropanol and 2-methoxyethanol, respectively.

Tri(isopropoxy)(vinyl)silane and tris(2 -methoxyethoxy)vinylsilane are within an analogue group of substances within which, in general, there is no evidence of any significant biodegradation once hydrolysis and subsequent biodegradation of the alkoxy groups has been taken into account.

This analogue group for the ready biodegradability endpoint consists of a number of sub-classes of substances (based on structure / functionality) with different main codes (used to represent the different sub-classes). However, read-across is carried out between substances with the same main code in most cases.

The table below presents ready biodegradation data for substances within the sub-class II-2. Both the registration substance and read-across substance are members of this class. It is therefore considered valid to read across the results for tris(2 -methoxyethoxy)vinylsilane (CAS 1067-53-4) to fill the data gap for the registered substance. Additional information is given in a supporting report (PFA, 2013f) attached in Section 13.

Table: Ready biodegradation data for substances within the relevant sub-class of chemicals

CAS	Name	Main code	Readily biodegradable? Yes/no	Result: Biodegradation after 28 days (%)	Guideline	Test type	Klimisch code	Corrected % biodegradation once alkoxy/acetoxy biodegradation is accounted for[1]
1067-53-4	Tris(2-methoxyethoxy)vinylsilane	II-2	Yes	89%	Annex V C4-A	DOC	1	7
18748-98-6	Trimethyl(octadecyloxy)silane	II-2-1	No	65%	OECD 301B	CO2	2	-21
157859-20-6	2-Propenoic acid, tris(1-methylethyl)silyl ester	II-2-1	No	9%	OECD 301F	BOD	1	-16

[1]The negative values in this column are where the biodegradation rate observed in the test is less than that expected assuming only alkoxy/acetoxy parts biodegrade. This could be due to low solubility of parent substance or low rates of hydrolysis. These values should in effect be considered as zero.

In the key study with tris(2-methoxyethoxy)vinylsilane, 89% biodegradation was observed in 28 days, meeting the 10-day window.

Tris(2-methoxyethoxy)vinylsilane hydrolyses rapidly (half-life 61.5 min at pH 7 and 25°C) to vinylsilanetriol and 2-methoxyethanol. The biodegradation observed in the studies is attributable to the biodegradation of 2-methoxyethanol (CAS 109-86-4), which is readily biodegradable (reliable published literature cited in the disseminated REACH registration dossier as of May 2013; similar results are available in peer-reviewed secondary reference sources). The silanol hydrolysis product, vinylsilanetriol, is not expected to biodegrade to any significant extent.