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EC number: 297-566-6 | CAS number: 93642-68-3
Partition coefficient
Administrative data
Link to relevant study record(s)
Description of key information
log Kow [3-[3-(triethoxysilyl)propyl]oxolane-2,5-dione]: not relevant
log Kow [2-[3-(triethoxysilyl)propyl]butanedioic acid]: -0.8 at pH 7 and 20°C (QSAR)
log Kow [2-[3-(trihydroxysilyl)propyl]butanedioic acid]: -4.0 at pH 7 and 20°C (QSAR)
Log Kow [ethanol]: -0.3
Key value for chemical safety assessment
Additional information
The requirement to conduct an n-octanol/water partition coefficient for the substance is waived because in contact with water the substance hydrolyses very rapidly to form an intermediate ethoxysilane hydrolysis product, 2-[3-(triethoxysilyl)propyl]butanedioic acid. The ultimate hydrolysis products are 2-[3-(trihydroxysilyl)propyl]butanedioic acid and ethanol.
Predicted log Kow values of 2.0 at 20°C and -2.6 at 20°C were determined for the intermediate ethoxysilane hydrolysis product, 2-[3-(triethoxysilyl)propyl]butanedioic acid and ultimate silanol hydrolysis product, 2-[3-(trihydroxysilyl)propyl]butanedioic acid respectively, using a validated QSAR estimation method. This prediction refers to the unionised form of the substance. The butanedioic acid group in 2-[3-(triethoxysilyl)propyl]butanedioic acid will protonate in aqueous solution, therefore the estimated log Kow for the unionised form was corrected for ionisation using the equation provided in the ECHA Guidance R.7a (2008) and reported pKa value of 4.21 at 25°C (first ionisation) for butanedioic acid. At pH 2, pH 4, pH 7 and pH 9, the corrected log Kow values are 2.0, 1.8, -0.8 and -2.8 respectively. The relevant corrected log Kow values are used for risk assessment purposes.
Similarly, the ionised form of the ultimate hydrolysis product, 2-[3-(trihydroxysilyl)propyl]butanedioic acid has predicted log Kow values of -2.6, -2.8, -4.0 and -4.0 at pH 2, pH 4, pH 7 and pH 9 respectively.
Ethanol has a reported log Kow of -0.3 (Hansch 1995).
Hansch C 1995; Hansch C, Leo A and Hoekman D1995. Exploring QSAR. Hydrophobic, Electronic, and Steric Constants. ACS Professional Reference Book., American Chemical Society).
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