Registration Dossier
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EC number: 701-410-9 | CAS number: -
Dissociation constant
Administrative data
Link to relevant study record(s)
- Endpoint:
- dissociation constant
- Data waiving:
- study scientifically not necessary / other information available
- Justification for data waiving:
- the study does not need to be conducted because the substance is hydrolytically unstable (half-life less than 12 hours)
Reference
Description of key information
Dissociation constant [amino groups of the constituents]: approximately 10
Dissociation constant [silanol groups of hydrolysis products]: pKa approximately 10
Dissociation constant [amino groups of hydrolysis products]: 9.7 – 10.9
Key value for chemical safety assessment
Additional information
The requirement to test the substance for dissociation constant is waived because in contact with water the constituents of the substance are expected to hydrolyse moderately to rapidly to form their corresponding silanol hydrolysis products. The typical dissociation constants for the hydroxyl protons of silanetriols are available from studies in other silanetriols (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.
The dissociation constant of the amino groups of the constituents of the substance is expected to be approximately 10. Similarly, the amino groups of the silanol hydrolysis products have predicted dissociation constant of 9.7 - 10.9.
Reference:
PFA (2013b). Peter Fisk Associates, Dissociation constant Analogue report, PFA.300.001.001
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