Registration Dossier
Registration Dossier
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EC number: 242-472-2 | CAS number: 18643-08-8
Endpoint summary
Administrative data
Description of key information
Physico-chemical properties
Chlorodimethyloctadecylsilane is a solid at standard temperature and pressure, with a measured melting point of 25.7°C and a measured boiling point of 340.3°C. It has a measured density of 0.992 g/cm³ at 20°C and a predicted vapour pressure of 3.0E-04 hPa at 20°C.
The substance is not classified as flammable on the basis of a measured flash point of 114°C and the high boiling point. It has a measured auto-ignition temperature of 241°C, and is not explosive and not oxidising on the basis of chemical structure.
In contact with water, chlorodimethyloctadecylsilane is predicted to react very rapidly (half-life < 2 min at RT and pH 7) to produce octadecyldimethylsilanol and hydrochloric acid according to the following equation:
CH3(CH2)17Si(CH3)2Cl + H2O → CH3(CH2)17Si(CH3)2OH + HCl
Therefore the properties of the silanol hydrolysis product, octadecyldimethylsilanol are assessed instead. The hydrolysis product has very low solubility in water, 2.97E-05 mg/l (predicted), with a log Kow of 9.0 (predicted). It is considered to be slightly surface active. The hydrolysis product is less volatile than the parent substance (vapour pressure = 8.4E-06 Pa at 25°C).
Silanols may undergo condensation reactions to give siloxane dimers according to the scheme:
R3Si(OH) ⇄ R3SiOSiR3
(where R is an alkyl or aryl side-chain)
The degree of condensation that will occur may vary with:
- Concentration of the silanol; the greater the initial concentration, the greater the degree of condensation. Significant condensation is not expected at concentrations less than approximately 100 mg/l, but is dependent on specific conditions.
- pH, the condensation reaction may be either acid or base catalysed.
- Temperature.
- Other species present.
Additional information
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