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EC number: 216-467-0 | CAS number: 1591-02-2
- 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
Ecotoxicological Summary
Administrative data
Hazard for aquatic organisms
Hazard for air
Hazard for terrestrial organisms
Hazard for predators
Additional information
The hydrolysis half-life of dibutoxy(dimethyl)silane is <2 h at pH 7, 20-25°C. The registered substance will hydrolyse in contact with water and atmospheric moisture to dimethylsilanediol and n-butanol. REACH guidance (ECHA 2012, R.16) states that “for substances where hydrolytic DT50is less than 12 hours, environmental effects are likely to be attributed to the hydrolysis product rather than to the parent itself”. TGD and ECHA guidance, (EC 2003, ECHA 2012) also suggest that when the hydrolysis half-life is less than 12 hours, the breakdown products, rather than the parent substance, should be evaluated for aquatic toxicity. Therefore, the environmental hazard assessment, including sediment and soil compartments due to water and moisture being present, is based on the properties of the silanol hydrolysis product, in accordance with REACH guidance. As described in Sections 4.8 and 5.1.2, the silanol hydrolysis products may be susceptible to condensation reactions.
READ-ACROSS JUSTIFICATION
Read-across is proposed to fulfil REACH Annex VII requirements for the registered substance from substances that have similar structure and physicochemical properties. Ecotoxicological studies are conducted in aquatic medium or in moist environments; therefore the reactivity of the substance in water is particularly important, because after reaction in water occurs the resulting product has different structural features, physicochemical properties and structure.
Dibutoxy(dimethyl)silane (CAS 1591-02-2) undergoes a rapid hydrolysis reaction (half-life <2 hours at pH 7) toform the hydrolysis products dimethylsilanediol and n-butanol. Therefore, it is more relevant to assess the ecotoxicity of the dibutoxy(dimethyl)silane by reference to the properties of dimethylsilanediol (CAS 1066-42-8).Table 1 presents relevant physicochemical properties and the available ecotoxicological data.
Table 1: Summary of physicochemical and ecotoxicological properties of the registered and surrogate substances
CAS Number |
1591-02-2 |
1066-42-8 |
Chemical Name |
Dibutoxy(dimethyl)silane |
Dimethylsilanediol |
Si reaction product |
Dimethylsilanediol |
n/a (hydrolytically stable) |
Molecular weight (parent) g/mol |
204.39 |
92.17 |
Molecular weight (reaction product) g/mol |
92.17 |
n/a |
log Kow(parent) |
4.9 |
-0.38 |
log Kow(silanol reaction product) |
-0.38 |
n/a |
Water sol (parent) |
9.4 mg/l (QSAR) |
>1000 mg/l (QSAR), limited by condensation reactions |
Water sol (silanol reaction product) |
>1000 mg/l (QSAR), limited by condensation reactions |
n/a |
Vapour pressure (parent) |
30 Pa at 25°C (QSAR) |
7 Pa (QSAR) |
Vapour pressure (reaction product) |
7 Pa (QSAR) |
n/a |
Reaction t1/2at pH 7 and 25°C |
1.4 h |
n/a |
Reaction t1/2at pH 4 and 25°C |
<8 minutes (at 19.6°C) |
n/a |
Reaction t1/2at pH 9 and 25°C |
0.59 h |
n/a |
Short-term toxicity to fish (LC50) |
n/a |
>126 mg/l |
Short-term toxicity to aquatic invertebrates (EC50) |
n/a |
>117 mg/l |
Algal inhibition (ErC50and NOEC) |
n/a |
EC50: >118 and NOEC:≥118 mg/l |
Long-term toxicity to fish (NOEC) |
n/a |
n/a |
Long-term toxicity to aquatic invertebrates (NOEC) |
n/a |
n/a |
Read-across from dimethylsilanediol to dibutoxy(dimethyl)silane
Dibutoxy(dimethyl)silane (CAS 1591-02-2) will react in water to form dimethylsilanediol (CAS 1066-42-8) and n-butanol. The reaction rate half-life is <2 hours. The environmental hazard assessment is based on the registered substance silanol reaction product dimethysilanediol for which there are data. The E(L)C50values for dimethylsilanediol, presented in Table 1, indicate that it is not toxic to freshwater fish, invertebrates and algae at the highest concentrations tested (in excess of 100 mg/l). Dimethylsilanediol is unlikely to biodegrade.
Consideration of the non-silanol hydrolysis product n-butanol
The other hydrolysis product, n-butanol, is of low toxicity to aquatic organisms, with EC or LC50values in excess of 100 mg/l for fish, invertebrates and algae (OECD SIDS 2001 for n-Butyl Alcohol). Therefore it is not necessary to consider n-butanol further in the chemical safety assessment.
Reference:
OECD (2001) SIDS Initial Assessment Report for SIAM 13, n-Butyl Alcohol, CAS 71-36-3
Conclusion on classification
There are no data for the registered substance, however the substance hydrolyses rapidly to dimethylsilanediol and the hazard assessment is based on this substance. Dimethylsilanediol has reliable short-term E(L)C50 values of >117 mg/l for invertebrates and >118 mg/l for algae as well as a NOEC value of ≥118 mg/l for algae.
Dimethylsilanediol is not readily biodegradable.
These data are consistent with the following classification under Regulation (EC) No 1272/2008 (as amended) (CLP):
Acute toxicity: Not classified.
Chronic toxicity: Not classified
In addition the registered substance produces n-butanol as a hydrolysis product. Ecotoxicity data indicate that n-butanol is not classified for the environment since the short-term E(L)C50 values are in excess of 100 mg/L.
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