Registration Dossier
Registration Dossier
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EC number: 213-914-1 | CAS number: 1066-40-6
Endpoint summary
Administrative data
Description of key information
Additional information
Trimethylsilanol (TMS) is an organosilicon compound with no hydrolysable groups. TMS in the aqueous phase can react with itself in a condensation reaction to form hexamethyldisiloxane (HMDS, CAS 000107-46-0) and water. In aqueous solution, an equilibrium is established between TMS (monomer) and HMDS (dimer). The equilibrium of the reaction is in favour of TMS, particularly at low concentrations. This is supported by the results of an OECD 111 study in which HMDS was found to hydrolyse in water with a half-life of approx. 5 days at pH 7 to TMS. The condensation reactions of TMS are reversible unless the concentration of HMDS exceeds its solubility; in this case, HMDS forms a separate phase, driving the equilibrium towards HMDS. At a loading of 100 mg/l, >99.9% TMS is expected. At loadings above about 500-1000 mg/l the concentration of HMDS is predicted to exceed its solubility, resulting in formation of a separate phase. In addition, HMDS is a named impurity in the registration substance at concentrations between 0 and 15 % w/w. Therefore, the environmental hazard assessment is basedo n the properties of the parent substance in accordance with REACH guidance for Chemical Safety Assessment (ECHA, 2016).
REFERENCE:
ECHA (2016). REACH Guidance on Information Requirements and Chemical Safety Assessment Chapter R16: Environmental Exposure Assessment Version: 3.0. February 2016
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