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Physical & Chemical properties

Dissociation constant

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Description of key information

Dissociation constant (1,1,3,3-tetramethyldisiloxane): not relevant
Dissociation constant (dimethylsilanediol): ca. 12

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 substance hydrolyses very rapidly. The hydrolysis products in this case are dimethylsilanol (intermediate hydrolysis product) and dimethylsilanediol which is the ultimate product of hydrolysis and methanol. Silanols are not expected to undergo significant dissociation within the range of pH relevant in the environment or in vivo. Dimethylsilanediol is reported in a secondary source to have a first dissociation constant of 11.9.