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Physical & Chemical properties

Partition coefficient

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partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2012-08-30 to 2013-09-04
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
according to guideline
OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)
GLP compliance:
Type of method:
HPLC method
Partition coefficient type:
Analytical method:
high-performance liquid chromatography
Key result
log Pow
Partition coefficient:
30 °C
Remarks on result:
other: pH not reported

A. Verification of Method Calibration:

The capacity factors for the 12 reference substances were determined from a single injection of each solution. The reference substances (in Table 1) were used to verify the original calibration. A plot of predicted versus observed log Kow values for the 12 reference substances (correlation coefficient >0.9999) reflects the stability of the calibration and long-term reproducibility of the method. The results are considered acceptable since the observed log Kow was within 0.2 log units of the predicted value from the original calibration (range = 0.10 to 0.14). These results indicate that a full re-calibration of the method was not required prior to making measurements on the test substance.

B. Estimation of log Kow Value of Test Substance from HPLC Retention:

The HPLC retention time for the test substance was obtained from duplicate injections at a mobile phase flow rate of I mL/min. Using the retention time for the test substance and hold-up time measurements (shown in Table 3), a value of log k was calculated. The measured log k value was used to estimate a log Kow value using the calibration equation previously described. The results for the test substance were considered acceptable since the calculated log Kow values from the duplicate determinations were within 0.1 log units of each other. The retention data and resulting value of log Kow is summarised in Table 4.

 Table 3: Hold-up time (min) results for 1 mL/min flow rate


T0, no column

T0, column




Standard deviation







Table 4: Retention data and estimated log Kow value of test substance


tr (min)

log k


log Kow

average log Kow

Test substance






Test substance





A log Kow value of 3.09 at 30°C was determined for the substance in accordance with a relevant test method and in compliance with GLP. The result is considered to be reliable
Executive summary:

The n-octanol/water partition coefficient of 2,4 -hexadienoic acid, 3-(trimethoxysilyl) propyl ester was estimated by the HPLC retention correlation method. The log Kow values of a chemically diverse group of organic compounds and permethylsiloxanes were correlated previously to capacity factors on a Phenomenex Luna C18(2) column with an isocratic mobile phase of 60% acetonitrile 40% deionized water. This stationary phase with acetonitrile/water mobile phases has been shown to yield correlations having low standard error, and a low degree of class-specific bias for estimation of log Kow an additional term was included to account for the differential behavior of hydrogen bond donor solutes. For this study, a subset of 12 reference substances including bromoalkanes, alcohols, and methyl esters were used to verify the original calibration model between log Kow and the capacity factor, log k. The current results of the verification set showed very high correlation (>0.9999) with previous results for the set of reference substances. The results were considered acceptable since the differences between the original and currently predicted log Kow values for the verification set ranged from 0.10 to 0.14 log units. The resulting estimate of log Kow for 2,4 -hexadienoic acid, 3-(trimethoxysilyl) propyl ester was 3.09.

Description of key information

log Kow [3-(trimethoxysilyl)propyl-(2E,4E)-hexa-2,4-dienoate]: 3.09 at 30°C (OECD 117)
log Kow [3-(trihydroxysilyl)propyl-(2E,4E)-2,4-hexadienoate]: -0.3 at 20°C (QSAR)
log Kow [methanol]: -0.82 to -0.64

Key value for chemical safety assessment

Log Kow (Log Pow):
at the temperature of:
30 °C

Additional information

A measured log Kow value of 3.09 at 30°C was determined for the substance with the use of an HPLC estimation method in accordance with OECD 117 Test Guideline and in compliance with GLP. The test substance was dissolved in 100% acetonitrile for the HPLC analyses, at a concentration of 1% (v/v), and the solutions were vortexed for at least 30 seconds. Duplicate analyses were used to verify the uniformity of the test substance in acetonitrile. The test substance was stable in acetonitrile and the solution was analysed immediately after preparation. The result is considered to be reliable and is used for assessment purposes.

In contact with water, the substance hydrolyses rapidly to form 3-(trihydroxysilyl)propyl-(2E,4E)-2,4-hexadienoate and methanol.

The log Kow of the silanol hydrolysis product, 3-(trihydroxysilyl)propyl-(2E,4E)-2,4-hexadienoate was predicted to be -0.3 at 20°C using a validated QSAR estimation method.

Methanol has a reported log Kow of -0.82 to -0.64 (OECD 2004).


OECD (2004): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 18-20 October 2004, Methanol, CAS 67-56-1.