Registration Dossier
Registration Dossier
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EC number: 915-673-4 | CAS number: 211519-85-6
Dissociation constant
Administrative data
Link to relevant study record(s)
- Endpoint:
- dissociation constant
- Data waiving:
- study technically not feasible
- Justification for data waiving:
- the study does not need to be conducted because the substance has no ionic structure
Reference
Description of key information
Dissociation constant [constituents of the submission substance]: Not relevant
Dissociation constant [silanol hydrolysis products of the constituents]: approximately 10 (read across)
Key value for chemical safety assessment
Additional information
In accordance with Section 1 of REACH Annex XI, the study does not need to be conducted because there are no groups present in the molecule that are expected to ionize within an environmentally relevant range. Testing would also be technically difficult because the substance has very low water solubility and is hydrolytically unstable.
In contact with water the constituents of the submission substance hydrolyse moderately to slowly. The hydrolysis products are ethanol, and (3-{[3-(trihydroxysilyl)propyl]disulfanyl}propyl)silanetriol for the S2 constituent, (3-{[3-(trihydroxysilyl)propyl]trisulfanyl}propyl)silanetriol for the S3 constituent and [3-({[3-(trihydroxysilyl)propyl]disulfanyl}disulfanyl)propyl]silanetriol for the S4 constituent.
There are no reliable measured data for the dissociation constants of the silanol hydrolysis products. The typical dissociation constants for the hydroxyl protons of silanetriols are available from studies in other silanetriols.
It is appropriate to read-across dissociation constant data for the silanol hydrolysis products from phenylsilanetriol. This suggests that silanols are not expected to undergo significant dissociation within the range of pH relevant in the environment or in vivo.
Phenylsilanetriol has a measured first dissociation constant ca. 10 in a reliable study using a relevant test method. Additional information is given in a supporting report (PFA 2013b) attached in Section 13.
Reference:
PFA (2013b). Peter Fisk Associates, Dissociation constant Analogue report, PFA.300.001.001
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