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Partition coefficient

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Description of key information

log Kow:  >9.268-9.508 (overall weighted average of >9.411) (OECD 123)

Key value for chemical safety assessment

Log Kow (Log Pow):
at the temperature of:
25 °C

Additional information

The log Kow of the submission substance (L6, CAS 107-52-8) has been read-across from data available for another structurally-related substance, dodecamethylpentasiloxane (L5, CAS No. 141 -63 -9). Both substances are linear siloxane chains with six and five silicon atoms respectively, with methyl branches and alternated by oxygen. Both substances undergo slow hydrolysis in water to form the same silanol hydrolysis products, dimethylsilanediol and trimethylsilanol. In addition, both substances have similar impurities and the percentage purities of both L6 and L5 are similar (>95% and >93% respectively). It is therefore, considered appropriate to read-across the measured partition coefficient data for L5 to L6.

A measured log Kow value ranging from 9.268 -9.508, with an overall variance-weighted average value of 9.411was determined for L5 using a relevant test method and in compliance with GLP. Since, L6 has six silicon atoms and higher molecular weight than L5, the log Kow value of L6 is expected to be >9.41. The result is considered to be reliable and was selected as key study.

For L6, the read-across is supported by a predicted log Kow value of >9.0 at 20°C which was determined using a validated QSAR estimation method.

In a secondary source to which reliability could not be assigned, a log Kow value of 6.6 was reported for the submission substance.