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Physical & Chemical properties

Dissociation constant

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Description of key information

Dissociation constant (parent, amine group): 10.65
Dissociation constant (silanol hydrolysis product): approximately 10, based on read-across from phenylsilanetriol

Key value for chemical safety assessment

pKa at 20°C:
10.65

Additional information

The requirement to test the substance for dissociation constant is waived because in contact with water the substance rapidly hydrolyses to form 3-(N-butylamino)propylsilanetriol and methanol.

A dissociation constant value of 10.65 for the amine group was reported for the substance in published data which has been subject to peer review (estimated value). The result is considered to be reliable.

There are no reliable measured data for the dissociation constant of 3-(N-butylamino)propylsilanetriol. 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-(N-butylamino)propylsilanetriol 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, (reliability 1; read-across conclusion is given reliability 2). Additional information is given in a supporting report, PFA (2013b) attached in Section 13 of the REACH technical dossier.