Registration Dossier
Registration Dossier
Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.
The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.
Use of this information is subject to copyright laws and may require the permission of the owner of the information, as described in the ECHA Legal Notice.
EC number: 249-385-9 | CAS number: 29043-70-7
Biodegradation in water: screening tests
Administrative data
Link to relevant study record(s)
Description of key information
Biodegradation in water (screening tests): 65% in 28 days (OECD 301B) read-across from a structurally related substance.
Key value for chemical safety assessment
- Biodegradation in water:
- readily biodegradable but failing 10-day window
Additional information
There are no reliable ready biodegradation data available for dimethylbis(octadecyloxy)silane (CAS 29043-70-7), therefore good quality data for the structurally-related substance, trimethyl(octadecyloxy)silane (CAS 18748-98-6), have been read across.
The target and source substance have similar physico-chemical properties and hydrolysis rates; both are very poorly soluble, low volatility and highly absorbing. Hydrolysis rates of >15 h are predicted for both substances. The target substance, dimethylbis(octadecyloxy)silane (CAS 29043-70-7), has two octadecyloxy groups and two methyl groups bonded to a central silicon atom. The source substance, trimethyl(octadecyloxy)silane has a central silicon atom substituted by one octadecyloxy group and three methyl groups. Both substances are predicted to hydrolyse at a similar rate (>15 hours), though hydrolysis rates in the environment are expected to be slower and limited by the high absorption potential and low solubility of the substances. Dimethylbis(octadecyloxy)silane and trimethyl(octadecyloxy)silane have structurally similar silanol hydrolysis products, dimethylsilanediol and trimethylsilanol respectively, whilst the non-silanol hydrolysis product is octadecanol for both substances. Octadecanol is considered to be inherently biodegradable (OECD 1993). Any biodegradation observed for the parent can be attributed principally to the C18 hydrocarbon chain. Since the source substance contains one octadecyloxy group, whilst the target substance contains two octadecyloxy groups, the read-across can be considered conservative.
It is therefore considered valid to read-across the results for trimethyl(octadecyloxy)silane (CAS 18748-98-6) to fill the data gap for the registered substance.
In the study with trimethyl(octadecyloxy)silane (CAS 18748-98-6) 65% biodegradation was observed in 28 days. The study was conducted according to OECD Guideline 301B and is considered reliable. This is selected as the key study.
OECD (1993): Screening Information Data Set (SIDS) of 1-octadecanol (CAS No 112-92-5). OECD High Production Volume Chemicals Programme (1993).
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
