Registration Dossier
Registration Dossier
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EC number: 208-765-4 | CAS number: 541-05-9
Partition coefficient
Administrative data
Link to relevant study record(s)
Description of key information
log n-octanol-water partition coefficient (hexamethylcyclotrisiloxane): 4.4 (calculated)
log n-octanol-water partition coefficient (L3-diol): 3.2 (QSAR)
log n-octanol-water partition coefficient (DMSD): -0.38 at 20°C (measured)
Key value for chemical safety assessment
- Log Kow (Log Pow):
- 4.4
- at the temperature of:
- 20 °C
Additional information
The substance is hydrolytically unstable (half-life at pH 7 and 25°C = 23 min) and, therefore, the log Kow of the hydrolysis products are more relevant than that of the substance.
A log Kow of 3.2 was determined for the intermediate silanol hydrolysis product L3-diol using an appropriate estimation method. The result is considered reliable.
The log Kowof the final hydrolysis product, dimethylsilanediol, was determined to be -0.38 at 20°C using a relevant test method The result is considered to be reliable.
The log octanol-water partition coefficient of the parent substance, D3, has been calculated to be 4.4 (Dow Corning 2007). A measured log Kow of 3.9 has been reported (Bruggeman 1984), however, there is not enough information to validate the HPLC method used for use with siloxane substances and recent measurements for other siloxanes indicate that the HPLC method underestimates the log Kow.
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