Registration Dossier
Registration Dossier
Data platform availability banner - registered substances factsheets
Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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.
Diss Factsheets
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: 242-171-6 | CAS number: 18293-82-8
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
Endpoint summary
Administrative data
Description of key information
Key value for chemical safety assessment
Skin sensitisation
Endpoint conclusion
- Endpoint conclusion:
- no adverse effect observed (not sensitising)
- Additional information:
There are no sensitisation data for the registered substance so data has been read-across from the structurally similar read-across substance isobutyl(trimethoxy)silane.
In a traditional Buehler skin sensitisation study to GLP (Hüls, 1993d) twenty Dunkin-Hartley guinea-pigs were exposed to three separate induction phases on their shaved left flanks. On Day 0 undiluted test substance was applied under an occlusive patch for six hours. On Days and 14 this process was repeated with a 50% solution in corn oil and after each application the skin was monitored for reactions. Ten negative controls had patches with corn oil only applied to their left flanks. On Day 28 both negative controls and test animals had an occlusive patch of 50% test substance (in corn oil) applied to their right flanks for 6 hours. The skin was then assessed at 6, 24, 48 and 72 hours after administration. There were no skin reactions in any of the test or negative control animals during the challenge phase and it was concluded that isobutyl(trimethoxy)silane is not a skin sensitiser.
To reduce animal testing REACH recommends to make use of a read-across approach where appropriate based on the high accordance in properties relevant for the specific endpoint. In the case of acutetoxicity the relevant properties are structural similarity, physical-chemical parameters in the same range and they hydrolyse to similar silicon-containing hydrolysis products. In the following paragraphs the proposed read-across from isobutyl(trimethoxy)silane to isobutyl(dimethoxy)methylsilane is evaluated point by point.
Read-across hypothesis
The hypothesis is that the source and target substances have similar toxicological properties because they are structurally similar and have similar physicochemical properties. This is discussed further below and additional information is given in supporting reports (PFA, 2013aa and PFA, 2015t).
Isobutyl(dimethoxy)methylsilane hydrolyses rapidly, with calculated hydrolysis half-lives of 0.2 hours at pH 4, 1.7 hours at pH 7 and 0.04 hours at pH 9 and 25°C. At 37.5ºC and pH 7 the calculated hydrolysis half-life is approximately 0.6 hours. At 37.5ºC and pH 2 the hydrolysis half -life is approximately 5 seconds. At 37.5ºC and pH 4 the calculated hydrolysis half-life is 0.07 hours. At 37.5ºC and pH 5.5 (relevant for dermal exposure), the hydrolysis half -life will be in between the half-lives at pH 4 and pH 7 at 37.5ºC. The products of hydrolysis are isobutyl(methyl)silanediol and methanol.
Isobutyl(trimethoxy)silane (CAS 18395-30-7) hydrolyses rapidly, with calculated hydrolysis half-lives of 0.2 hours at pH 4, 4.1 hours at pH 7 and 0.1 hours at pH 9 and 25°C. At 37.5ºC and pH 7 the calculated hydrolysis half-life is approximately 1.5 hours. At 37.5ºC and pH 2 the hydrolysis half -life is approximately 5 seconds. At 37.5ºC and pH 4 the calculated hydrolysis half-life is 0.07 hours. At 37.5ºC and pH 5.5 (relevant for dermal exposure), the hydrolysis half -life will be in between the half-lives at pH 4 and pH 7 at 37.5ºC. The products of hydrolysis are (2-methylpropyl)silanetriol and methanol.
The non-silanol hydrolysis product, methanol, does not contribute to any adverse effects for acute toxicity at the relevant dose levels based on publicly available information (OECD 2004a).
Read-across justification
(a) Structural similarity
The registration and read-across substance are structurally similar and are members of a structural class of alkoxysilane substances. The registered substance, isobutyl(dimethoxy)methylsilane, has two methoxy groups bound to silicon, the read-across substance, isobutyl(trimethoxy)silane, has three methoxy groups. The registration and read-across substance both have an identical hydrocarbon side-chain (isobutyl) bound to the silicon, and the registration substance also has a methyl group attached. Both substances hydrolyse rapidly to produce the similar silicon-containing hydrolysis products, isobutyl(methyl)silanediol or (2-methylpropyl)silanetriol, and methanol.
(b) Similar physicochemical characteristics
The key physicochemical parameters are summarised below.
Table: Key physicochemical parameters
-
Target (registration substance)
Source (read-across substance
CAS number
18293-82-8
18395-30-7
EC number
242-171-6
242-272-5
Chemical Name
Isobutyl(dimethoxy)methylsilane
Isobutyl(trimethoxy)silane
Molecular weight
(gmol-1)162.31
178.31
log Kow
Waived because the substance hydrolyses rapidly in water to form isobutyl(methyl)silanediol and methanol..
Isobutyl(dimethoxy)methylsilane has a calculated log Kowof 3.4.
A log Kowof 1.0 has been calculated for the silanol hydrolysis product.
Methanol has a measured log Kowof -0.82 to -0.64
Waived because the substance hydrolyses rapidly in water to form (2 -methylpropyl)silanetriol and methanol.
Isobutyl(trimethoxy)silane has a calculated log Kowof 2.1.
A log Kowof -1.0 has been calculated for the silanol hydrolysis product.
Methanol has a measured log Kowof -0.82 to -0.64
Water solubility at 20°C
Waived because the substance hydrolyses rapidly in water to form isobutyl(methyl)silanediol and methanol.
Isobutyl(methyl)silanediol has a calculated water solubility of 8.1E+04 mg/l. However, the saturation concentration is limited by condensation reactions above approximately 100mg/l.
Methanol is miscible in water.
Waived because the substance hydrolyses rapidly in water to form (2 -methylpropyl)silanetriol and methanol.
(2 -methylpropyl)silanetriol is predicted to be very soluble, however solubility is expected to be limited by condensation reactions.
Methanol is miscible in water.
Vapour pressure at 20°C
Isobutyl(dimethoxy)methylsilane has a calculated vapour pressure of 310 Pa at 25°C.
Isobutyl(methyl)silanediol has a calculated vapour pressure of 0.33Pa at 25°C.
Methanol has a measured vapour pressure of 12790Pa.
Isobutyl(trimethoxy)silane has a calculated vapour pressure of 190 Pa at 25°C.
((2-methylpropyl)silanetriol) has a calculated vapour pressure of 0.00294 Pa at 25°C.
Methanol has a measured vapour pressure of 12790Pa.
PFA (2013a). Peter Fisk Associates, Application of Category - Analogue - QSAR for Reconsile, PFA.300.006.014
PFA, (2015t). Peter Fisk Associates, Analogue report – mammalian toxicity of alkyl alkoxysilanes, PFA.404.002.002.
Migrated from Short description of key information:
In a sensitisation study conducted according to an appropriate guideline and in compliance with GLP the read-across substance isobutyl(trimethoxy)silane was found to be non-sensitising. These data are read across to isobutyl(dimethoxy)methylsilane.
Justification for selection of skin sensitisation endpoint:
Study was conducted according to an appropriate OECD test guideline and in compliance with GLP.
Respiratory sensitisation
Endpoint conclusion
- Endpoint conclusion:
- no study available
Justification for classification or non-classification
Based on the available read-across data from isobutyl(trimethoxy)silane, the registered substance isobutyl(dimethoxy)methylsilane does not require classification for sensitisation according to Regulation (EC) No. 1272/2008.
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.