Triethoxy(methyl)silane

Biodegradation in water: screening tests

Description of key information

74 % biodegradation in 21 days; based on RA to triacetoxyethylsilane (CAS 17689 -77 -9)

Hydrolysis product ethanol: readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

There are no reliable ready biodegradation data available for triethoxy(methyl)silane, therefore good quality data for the analogue substance, triacetoxyethylsilane (CAS 17689 -77 -9), have been read across. Both substances hydrolyse to structurally-related silanol hydrolysis products, methylsilanetriol and ethylsilanetriol. The other hydrolysis products being ethanol and acetic acid, respectively.

 

Therefore, triethoxy(methyl)silane hydrolyzes rapidly into ethanol which is readily biodegradable and methylsilanetriol which is not. Both triethoxy(methyl)silane and triacetoxyethylsilane are within an analogue group of substances within which, in general, there is no evidence of any significant biodegradation once biodegradation of alkoxy/acetoxy groups has been taken into account.

 

It is therefore considered valid to read-across the results for triacetoxyethylsilane to fill the data gap for the registered substance. This wider analogue group for the ready biodegradability endpoint consists of a number of sub-classes of substances. However, read-across is carried out between substances with the same sub-class in most cases.

 

Table 4.1.4 presents ready biodegradation data available for substances within the sub-class of alkoxysilanes, silanols, acetoxysilanes and chlorosilanes, etc, where the Si part is of low-biological reactivity, once any hydrolysis has been taken into account. Both triethoxy(methyl)silane and triacetoxyethylsilane are members of this sub-class.

 

Additional information is given in a supporting report (PFA, 2013) attached in Section 13 of the IUCLID dossier.

 

A biodegradation rate of 74% in 21 days (DOC removal) was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP (1995). Triacetoxyethylsilane hydrolyses very rapidly in water, to produce acetic acid, which would biodegrade rapidly (six of the eight carbons in triacetoxyethylsilane are converted to acetic acid in a rapid hydrolysis reaction). The silanol hydrolysis product, ethylsilanetriol, is not expected to biodegrade to any significant extent. The study is considered to be reliability 1 (reliable without restrictions); the read across of the result is considered to be reliability 2 (reliable with restrictions).

Table 4.1.4 Ready biodegradation data available for substances within the relevant sub-class of chemicals.

CAS	Name	Readily biodegradable? Yes/No	Result: Biodegradation after 28 days	Guideline	Reliability	Corrected % biodegradation once alkoxy/acetoxy biodegradation is accounted for
001066-40-6	Hydroxytrimethylsilane	No	0%	OECD 310	1a	0
018748-98-6	Trimethyl(octadecyloxy)silane	No	68%	OECD 301B	1a	-18
017689-77-9	Triacetoxyethylsilane	Yes	74% in 21 days	EC C4-A	1a	-1
001067-25-0	Trimethoxypropylsilane	No	54%	Annex V C4-A	1a	4
002943-75-1	Triethoxyoctylsilane	No	31.5%	OECD 301D	1a	-11
016415-13-7	Triethoxyhexadecylsilane	No	43%	MITI	1c	16
087135-01-1	1,6-Bis(trimethoxysilyl)hexane	Yes, but not meeting 10-day window	74%	OECD 301B	1a	24
None45	Mixture of 1,1- and 1,2-bis(trimethoxysilyl)ethane	Yes	93%	"Biodegradation study of chemical substances by microorganisms and the like " stipulated in "Testing Method for New Chemical Substances etc." ( Kanhogyo No.5, Yakuhatsu 615, 49Kikyoku No.392, July 13, 1974 )	1a	18
013154-25-1	Chlorotri(3-methyl-propyl)silane	No	0%	OECD 301B	1a	0
035435-21-3	Triethoxy(2,4,4-trimethylpentyl)silane	No	13%	OECD310	1a	-30
018395-30-7	Trimethoxy(2-methylpropyl)silane	No	36 - 47%	OECD 301B	1a	4
142877-45-0	Silane, trimethoxy(1,1,2-trimethylpropyl)-	No	31%	OECD 301D	1a	-2
017980-47-1	Triethoxyisobutylsilane	Yes	75%	OECD 301D	1a	15
126990-35-0	Dicyclopentyldimethoxysilane	No	12%	OECD 301C	1	-5
139147-73-2	Silane, dichlorodicyclopentyl-	No	0.8%	OECD 301D	2b	1
017865-32-6	Cyclohexyldimethoxymethylsilane	No	15-17%	OECD 301D	1a	-5
None46	t-butoxycyclopentyldimethoxysilane	No	15%	OECD 301C	1a	7
000098-12-4	Cyclohexyltrichlorosilane	No	0%	OECD 301C	1a	0
000124-70-9	Dichloro(methyl)(vinyl)silane	No	-6.78%	OECD 301 A	1a	0
001067-53-4	Tris(2-methoxyethoxy)vinylsilane	Yes	89%	Annex V C4-A	1a	7
002768-02-7	Trimethoxyvinylsilane	No	51%	OECD 301F	1a	-9