Registration Dossier
Registration Dossier
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EC number: 273-054-8 | CAS number: 68937-17-7
Hydrolysis
Administrative data
Link to relevant study record(s)
Description of key information
Hydrolysis half-life of Si-Cl at pH 4, 7 and 9: very rapid, producing silanols. The Si-Si bond is also expected to be highly unstable.
Key value for chemical safety assessment
Additional information
No hydrolysis study is available fordisilane, chloro Me derivs.However, a reliable study according to OECD 111 is available for the related substance dichloro(dimethyl)silane. This substance is fully hydrolysed within a few minutes at pH 4, 7 and 9 and 1.5°C.Hydrolysis rates increase with temperature; therefore it can be concluded that the half-life at 25°C is <1 min at pH 4, 7 and 9.Data from the category of chlorosilanes suggests that hydrolysis is very rapid and vigorous for all chlorosilanes. Therefore, it can be concluded that each component of the submission substance will hydrolyse rapidly under environmentally-relevant conditions.
The expected first reactions are:
MeSi(Cl)2Si(Me)Cl2→ MeSi(OH)2Si(Me)(OH)2
Me2Si(Cl)Si(Me)Cl2→ Me2Si(OH)Si(Me)(OH)2
Me2Si(Cl)Si(Me)2Cl → Me2Si(OH)Si(Me)2(OH)
However, given that the cleaving of the Si-Si bond to give two Si-O bonds is highly thermodynamically-favoured, it can be envisaged that under environmental conditions, methylsilanetriol and dimethylsilanediol would soon be formed, with the amount of the triol being higher than the diol because of the proportions of the three constituents present in the reaction mass. These substances have been assessed as the breakdown products of the REACH-registered chlorosilane precursors trichloro(methyl)silane (CAS 75-79-6) and dichlorodimethylsilane (CAS 75-78-5).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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