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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

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Diss Factsheets

Physical & Chemical properties

Dissociation constant

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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)

Description of key information

Dissociation constant [tris(2-methoxyethoxy)(vinyl)silane]: Not relevant due to rapid hydrolysis in contact with water

Dissociation constant [vinylsilanetriol]: pKa approximately 10

Key value for chemical safety assessment

Additional information

The requirement to conduct a dissociation constant study for the substance is waived because in contact with water, the substance hydrolyses rapidly. The hydrolysis products in this case are vinylsilanetriol and 2-methoxyethanol.

There are no reliable measured data for the dissociation constant of vinylsilanetriol. 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 vinylsilanetriol 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 of the REACH technical dossier.

2 -Methoxyethanol has a first dissociation constant of 14.8 at 25°C, reported in a secondary source (Serjeant 1979).


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

Serjeant, E.P., Dempsey B (1979). Ionisation Constants of Organic Acids in Aqueous Solution. International Union of Pure and Applied Chemistry (IUPAC). IUPAC Chemical Data Series No. 23, 1979. New York, New York: Pergamon Press, Inc., p. 46