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Dissociation constant

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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
the study does not need to be conducted because the substance is insoluble

Description of key information

Dissociation constant [triethoxy(2,4,4-trimethylpentyl)silane]: Not relevant

Dissociation constant [(2,4,4-trimethylpentyl)silanetriol]: pKa approximately 10

Key value for chemical safety assessment

Additional information

The requirement to test the substance for dissociation constant is waived because there are no ionisable groups present in the molecule. However, in contact with water the substance hydrolyses moderately to form (2,4,4-trimethylpentyl)silanetriol and ethanol.

There are no reliable measured data for the dissociation constant of (2,4,4-trimethylpentyl)silanetriol. 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 (2,4,4-trimethylpentyl)silanetriol 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 approximately 10 in a reliable study using a relevant test method. Additional information is given in a supporting report (PFA, 2013b) attached in Section 13.


PFA (2013b). Peter Fisk Associates, Dissociation constant Analogue report, PFA.300.001.001