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EC number: 916-331-7 | CAS number: -
Adsorption / desorption
Administrative data
Link to relevant study record(s)
Description of key information
Log Koc of Cyclabute is 3.5 using Cyclaprop and Cyclobutanate as well as QSAR predictions.
Key value for chemical safety assessment
- Koc at 20 °C:
- 3 162
Additional information
First the executive summaries on the Koc of two analogues, Cyclobutanate and Cyclaprop, will be presented and thereafter the derivation of the log Koc of Cyclabute
Cyclobutanate and its experimental log Koc
The adsorption coefficient of Cyclobutanate was investigated according to OECD guideline 121 using the HPLC method under GLP. The log Koc of Cyclobutanate was found to be 3.18.
Cyclaprop and its experimental log Koc
The adsorption of Cyclaprop to soil/sludge was investigated according to OECD guideline 121 using the HPLC method under GLP. The log Koc of the major compound was found to be 3.11 (Koc 1300) at neutral pH. The log Koc's for impurities I, II and III were found to be 1.86, 2.18 and 2.99 respectively.
The Koc of Cyclabute using Kocs of Cyclobutanate and Cyclaprop as well as QSAR calculations (IFF, 2017)
Introduction: Experimental adsorption/desorption information is not available for Cyclabute. Information on measured Kocs from Cyclobutanate, other Cycla-esters and QSAR predictions will be used to predict the Koc of Cyclabute. The Cycla-esters all have a tricyclodecenyl backbone and an ester bond to which an alkyl chain is attached. This alkyl chain can be an acetic (Cyclacet), propanoic (Cyclaprop), butanoic (Cyclobutanate) or isobutanoic group (Cyclabute) group. The increase in chain length will have an increase in the respective Koc values.
Method: At first a direct read across from Cyclobutanate was planned. However, in view of differences in experimental Log Kows between the butanoic and the isobutanoic group of these esters, it seemed more appropriate to look at the incremental increase in log Kow and Koc across these esters to predict the Koc value for Cyclabute.
Experimental and predicted Log Kow and Log Koc are used to retrieve the most appropriate value for Cyclabute. For the prediction of the Log Koc, three types of QSARs are used: the EpiSuite Koc model, the EUSES Log Koc model for 1) non-hydrophobics and 2) for esters.
For the EpiSuite Koc model, the EpiSuite Log Kow was included in the prediction.
The equations of EUSES used are:
Predominantly hydrophobics: logKoc = 0.10 + 0.81 * logKow (n = 81; r2 = 0,887; s = 0,451)
Esters: logKoc = 1.09 + 0.47 * logKow (n = 216; r2 = 0,681; s = 0,425),
as presented in Hansler et al., 2006 (and these equations are the same as presented in Lijzen and Rikken, 2004 and derived from Sablic, 1995).
Results: In the table below the experimental Log Kows and experimental and predicted Log Kocs are presented. It can be seen that the predicted Log Koc with EpiSuite and the EUSES model for esters of Cyclacet, Cyclaprop and Cyclobutanate are more close to the experimental Log Koc values than the QSAR for predominantly hydrophobics. Therefore the predicted results from the 'predominantly hydrophobics' will not be used for Koc prediction of Cyclabute.
The EUSES model for esters is well predicting the Koc of Cyclobutanate and seems to be the most appropriate prediction model. In view of the slightly higher measured log Kow of Cyclabute, compared to Cyclobutanate, the predicted Log Koc value of 3.5 will be used for risk assessment instead of a direct read across from Cyclobutanate.
Discussion: The experimental Log Kow of Cyclobutanate is slightly lower than what is expected from the overall category. This may, partly, be due to the shake flask method which was only used for Cyclobutanate, while for all others the HPLC method was used. The log Koc values of all substances other than Cyclabute have been determined with the HPLC method and thus limited uncertainty is expected for this value. It can be seen that with each extra methyl group in the Cycla-esters the Log Koc increases with circa 0.2-0.3 in the experimental values and in the QSAR values. Therefore the Log Koc of 3.5 for Cyclabute is justified.
|
| Exp. Log Kow | Exp. Log Koc | Pred. Log Koc (EUSES- esters) | Pred. Log Koc (KocWin) | Pred. Log Koc (EUSES-hydrophobics) |
Cyclacet | Acetic | 3.9 | 2.62 | 2.9 | 2.5 | 3.3 |
Cyclaprop | Propanoic | 4.4 | 3.11 | 3.15 | 2.7 | 3.7 |
Cyclobutanate | Butanoic | 4.48 | 3.18 | 3.2 | 3 | 3.7 |
Cyclabute | Isobutanoic | 5.1 | Data gap | 3.5 | 3 | 4.2 |
Hansler, R.J., Traas, T.P., and Mennes, W.C., 2006,Handreiking voor de afleiding van indicatieve milieukwaliteitsnormen,RIVM rapport 601503024/2006, Bilthoven, The Netherlands
[LogKoc: 3.5]
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