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Physical & Chemical properties

Dissociation constant

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Reference
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

Description of key information

Dissociation constant [triethoxy(3-thiocyanatopropyl)silane]: Not relevant


Dissociation constant [(3-thiocyanatopropyl)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 group present in the molecule that are expected to ionize within an environmentally relevant pH range. However, in contact with water, the substance hydrolyses moderately. The hydrolysis products in this case are (3-thiocyanatopropyl)silanetriol and ethanol.

There are no reliable measured data for the dissociation constant of (3-thiocyanatopropyl)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 (3-thiocyanatopropyl)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 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