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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
In key acute oral and inhalation studies conducted according to appropriate guidelines and in compliance with GLP on read-across substance isobutyl(trimethoxy)silane, the LD50 (oral) was found to be > 2000 mg/kg bw and the LC50 (inhalation, 4 hour) was found to be > 11000 mg/m3. These data are read across to isobutyl(dimethoxy)methylsilane.
Key value for chemical safety assessment
Acute toxicity: via oral route
Endpoint conclusion
- Endpoint conclusion:
- no adverse effect observed
- Dose descriptor:
- LD50
- Value:
- 2 000 mg/kg bw
Acute toxicity: via inhalation route
Endpoint conclusion
- Endpoint conclusion:
- no adverse effect observed
- Dose descriptor:
- LC50
- Value:
- 11 000 mg/m³ air
Acute toxicity: via dermal route
Endpoint conclusion
- Endpoint conclusion:
- no study available
Additional information
There are no acute toxicity data for the registered substance so data have been read-across from the structurally similar read-across substance isobutyl(trimethoxy)silane.
In the key acute oral toxicity study (Hüls, 1993a) conducted to OECD test guideline 401 (now deleted) and GLP, the oral LD50 was greater than 2000 mg/kg bw in male and female rats. Within the first three hours after administration in males and the first six hours in females, there were signs of toxicity. Within three (males) or six (females) hours there were signs of ruffled fur, crouching posture, mild sedation, ataxia, and swaying motion. By five to six hours there were no signs clinical in 8/10 animals. Six hours after administration, one female was noted with ruffled fur, medium to heavy sedation, ataxia, prone position, hypothermia, laboured breathing, closed eyes and chromodacryorrhea and was also inappetant. After 24 hours there were no remarkable signs in any of the animals.
In the key acute inhalation study (DCC, 1984) that was comparable to OECD 403 and to GLP, the 4 -hour LC50 was greater than 1525 ppm (ca. 11000 mg/m3) (the only concentration tested) in Sprague-Dawley rats. The animals were lethargic and unresponsive during the exposure period. However, on removal from the chamber, the animals quickly recovered and did not show any stress or signs of toxicity during the 14-day observation period.
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 (relevant for lungs and blood) the calculated hydrolysis half-life is approximately 0.6 hours. At 37.5ºC and pH 2 (relevant for conditions in the stomach following oral exposure), the hydrolysis half -life is approximately 5 seconds. At 37.5ºC and pH 4 the calculated hydrolysis half-life is 0.07 hours. 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 (relevant for lungs and blood) the calculated hydrolysis half-life is approximately 1.5 hours. At 37.5ºC and pH 2 (relevant for conditions in the stomach following oral exposure), the hydrolysis half -life is approximately 5 seconds. At 37.5ºC and pH 4 the calculated hydrolysis half-life is 0.07 hours. 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 (lethality) 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 |
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 Kow of 3.4. A log Kow of 1.0 has been calculated for the silanol hydrolysis product. Methanol has a measured log Kow of -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 Kow of 2.1. A log Kow of -1.0 has been calculated for the silanol hydrolysis product. Methanol has a measured log Kow of -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 100 mg/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 0.33 Pa at 25°C.Methanol has a measured vapour pressure of 12790 Pa. |
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 12790 Pa. |
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.
Justification for selection of acute toxicity – oral endpoint
The study was carried out in accordance with an appropriate OECD test guideline and in compliance with GLP.
Justification for selection of acute toxicity – inhalation endpoint
The study was carried out in accordance with an appropriate OECD test guideline and in compliance with GLP.
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 acute toxicity 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.
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